README
======

  This README file describes the port of NuttX to the SAMA5D3x-EK
  development boards. These boards feature the Atmel SAMA5D3
  microprocessors.  Four different SAMA5D3x-EK kits are available

    - SAMA5D31-EK with the ATSAMA5D31 (http://www.atmel.com/devices/sama5d31.aspx)
    - SAMA5D33-EK with the ATSAMA5D33 (http://www.atmel.com/devices/sama5d33.aspx)
    - SAMA5D34-EK with the ATSAMA5D34 (http://www.atmel.com/devices/sama5d34.aspx)
    - SAMA5D35-EK with the ATSAMA5D35 (http://www.atmel.com/devices/sama5d35.aspx)

  The each consist of an identical base board with different plug-in
  modules for each CPU.  I also have a 7 inch LCD for my SAMA5D3x-EK, but this
  is not yet generally available..

    SAMA5D3 Family

                              ATSAMA5D31    ATSAMA5D33    ATSAMA5D34    ATSAMA5D35
    ------------------------- ------------- ------------- ------------- -------------
    Pin Count                 324           324           324           324
    Max. Operating Frequency  536           536           536           536
    CPU                       Cortex-A5     Cortex-A5     Cortex-A5     Cortex-A5
    Max I/O Pins              160           160           160           160
    Ext Interrupts            160           160           160           160
    USB Transceiver           3             3             3             3
    USB Speed                 Hi-Speed      Hi-Speed      Hi-Speed      Hi-Speed
    USB Interface             Host, Device  Host, Device  Host, Device  Host, Device
    SPI                       6             6             6             6
    TWI (I2C)                 3             3             3             3
    UART                      7             5             5             7
    CAN                       -             -             2             2
    LIN                       4             4             4             4
    SSC                       2             2             2             2
    Ethernet                  1             1             1             2
    SD / eMMC                 3             2             3             3
    Graphic LCD               Yes           Yes           Yes           -
    Camera Interface          Yes           Yes           Yes           Yes
    ADC channels              12            12            12            12
    ADC Resolution (bits)     12            12            12            12
    ADC Speed (ksps)          440           440           440           440
    Resistive Touch Screen    Yes           Yes           Yes           Yes
    Crypto Engine             AES/DES/      AES/DES/      AES/DES/      AES/DES/
                              SHA/TRNG      SHA/TRNG      SHA/TRNG      SHA/TRNG
    SRAM (Kbytes)             128           128           128           128
    External Bus Interface    1             1             1             1
    DRAM Memory               DDR2/LPDDR,   DDR2/LPDDR,   DDR2/LPDDR,   DDR2/LPDDR,
                              SDRAM/LPSDR   SDRAM/LPSDR   DDR2/LPDDR,   DDR2/LPDDR,
    NAND Interface            Yes           Yes           Yes           Yes
    Temp. Range (deg C)       -40 to 85     -40 to 85     -40 to 85     -40 to 85
    I/O Supply Class          1.8/3.3       1.8/3.3       1.8/3.3       1.8/3.3
    Operating Voltage (Vcc)   1.08 to 1.32  1.08 to 1.32  1.08 to 1.32  1.08 to 1.32
    FPU                       Yes           Yes           Yes           Yes
    MPU / MMU                 No/Yes        No/Yes        No/Yes        No/Yes
    Timers                    5             5             5             6
    Output Compare channels   6             6             6             6
    Input Capture Channels    6             6             6             6
    PWM Channels              4             4             4             4
    32kHz RTC                 Yes           Yes           Yes           Yes
    Packages                  LFBGA324_A    LFBGA324_A    LFBGA324_A    LFBGA324_A

Contents
========

  - Development Environment
  - GNU Toolchain Options
  - IDEs
  - NuttX EABI "buildroot" Toolchain
  - NuttX OABI "buildroot" Toolchain
  - NXFLAT Toolchain
  - Loading Code into SRAM with J-Link
  - Writing to FLASH using SAM-BA
  - Creating and Using NORBOOT
  - Buttons and LEDs
  - Serial Consoles
  - Networking
  - AT25 Serial FLASH
  - HSMCI Card Slots
  - USB Ports
  - USB High-Speed Device
  - USB High-Speed Host
  - SDRAM Support
  - NAND Support
  - AT24 Serial EEPROM
  - I2C Tool
  - CAN Usage
  - SAMA5 ADC Support
  - SAMA5 PWM Support
  - RTC
  - Watchdog Timer
  - TRNG and /dev/random
  - Touchscreen Testing
  - OV2640 Camera Interface
  - I2S Audio Support
  - SAMA5D3x-EK Configuration Options
  - Configurations
  - To-Do List

Development Environment
=======================

  Several possible development environments may be use:

  - Linux or OSX native
  - Cygwin unders Windows
  - MinGW + MSYS under Windows
  - Windows native (with GNUMake from GNUWin32).

  All testing has been performed using Cygwin under Windows.

  The source has been built only using the GNU toolchain (see below).  Other
  toolchains will likely cause problems.

GNU Toolchain Options
=====================

  The NuttX make system will support the several different toolchain options.

  All testing has been conducted using the CodeSourcery GCC toolchain.  To use
  a different toolchain, you simply need to add change to one of the following
  configuration options to your .config (or defconfig) file:

    CONFIG_ARMV7A_TOOLCHAIN_CODESOURCERYW=y  : CodeSourcery under Windows
    CONFIG_ARMV7A_TOOLCHAIN_CODESOURCERYL=y  : CodeSourcery under Linux
    CONFIG_ARMV7A_TOOLCHAIN_ATOLLIC=y        : Atollic toolchain for Windos
    CONFIG_ARMV7A_TOOLCHAIN_DEVKITARM=y      : devkitARM under Windows
    CONFIG_ARMV7A_TOOLCHAIN_BUILDROOT=y      : NuttX buildroot under Linux or Cygwin (default)
    CONFIG_ARMV7A_TOOLCHAIN_GNU_EABIL=y      : Generic GCC ARM EABI toolchain for Linux
    CONFIG_ARMV7A_TOOLCHAIN_GNU_EABIW=y      : Generic GCC ARM EABI toolchain for Windows

  The CodeSourcery GCC toolchain is selected with
  CONFIG_ARMV7A_TOOLCHAIN_GNU_EABIW=y and setting the PATH variable
  appropriately.

  If you are not using AtmelStudio GCC toolchain, then you may also have to
  modify the PATH in the setenv.h file if your make cannot find the tools.

  NOTE about Windows native toolchains
  ------------------------------------

  There are several limitations to using a Windows based toolchain in a
  Cygwin environment.  The three biggest are:

  1. The Windows toolchain cannot follow Cygwin paths.  Path conversions are
     performed automatically in the Cygwin makefiles using the 'cygpath'
     utility but you might easily find some new path problems.  If so, check
     out 'cygpath -w'

  2. Windows toolchains cannot follow Cygwin symbolic links.  Many symbolic
     links are used in Nuttx (e.g., include/arch).  The make system works
     around these problems for the Windows tools by copying directories
     instead of linking them.  But this can also cause some confusion for
     you:  For example, you may edit a file in a "linked" directory and find
     that your changes had no effect.  That is because you are building the
     copy of the file in the "fake" symbolic directory.  If you use a\
     Windows toolchain, you should get in the habit of making like this:

       make clean_context all

     An alias in your .bashrc file might make that less painful.

  3. Dependencies are not made when using Windows versions of the GCC.  This is
     because the dependencies are generated using Windows paths which do not
     work with the Cygwin make.

       MKDEP                = $(TOPDIR)/tools/mknulldeps.sh

  NOTE 1: Older CodeSourcery toolchains (2009q1) do not work with default
  optimization level of -Os (See Make.defs).  It will work with -O0, -O1, or
  -O2, but not with -Os.

  NOTE 2: The devkitARM toolchain includes a version of MSYS make.  Make sure that
  the paths to Cygwin's /bin and /usr/bin directories appear BEFORE the devkitARM
  path or will get the wrong version of make.

IDEs
====

  NuttX is built using command-line make.  It can be used with an IDE, but some
  effort will be required to create the project (There is a simple RIDE project
  in the RIDE subdirectory).

  Makefile Build
  --------------
  Under Eclipse, it is pretty easy to set up an "empty makefile project" and
  simply use the NuttX makefile to build the system.  That is almost for free
  under Linux.  Under Windows, you will need to set up the "Cygwin GCC" empty
  makefile project in order to work with Windows (Google for "Eclipse Cygwin" -
  there is a lot of help on the internet).

  Native Build
  ------------
  Here are a few tips before you start that effort:

  1) Select the toolchain that you will be using in your .config file
  2) Start the NuttX build at least one time from the Cygwin command line
     before trying to create your project.  This is necessary to create
     certain auto-generated files and directories that will be needed.
  3) Set up include pathes:  You will need include/, arch/arm/src/sam34,
     arch/arm/src/common, arch/arm/src/armv7-m, and sched/.
  4) All assembly files need to have the definition option -D __ASSEMBLY__
     on the command line.

  Startup files will probably cause you some headaches.  The NuttX startup file
  is arch/arm/src/sam34/sam_vectors.S.  You may need to build NuttX
  one time from the Cygwin command line in order to obtain the pre-built
  startup object needed by RIDE.

NuttX EABI "buildroot" Toolchain
================================

  A GNU GCC-based toolchain is assumed.  The files */setenv.sh should
  be modified to point to the correct path to the Cortex-M3 GCC toolchain (if
  different from the default in your PATH variable).

  If you have no Cortex-M3 toolchain, one can be downloaded from the NuttX
  SourceForge download site (https://sourceforge.net/projects/nuttx/files/buildroot/).
  This GNU toolchain builds and executes in the Linux or Cygwin environment.

  1. You must have already configured Nuttx in <some-dir>/nuttx.

     cd tools
     ./configure.sh sama5d3x-ek/<sub-dir>

  2. Download the latest buildroot package into <some-dir>

  3. unpack the buildroot tarball.  The resulting directory may
     have versioning information on it like buildroot-x.y.z.  If so,
     rename <some-dir>/buildroot-x.y.z to <some-dir>/buildroot.

  4. cd <some-dir>/buildroot

  5. cp configs/cortexm3-eabi-defconfig-4.6.3 .config

  6. make oldconfig

  7. make

  8. Edit setenv.h, if necessary, so that the PATH variable includes
     the path to the newly built binaries.

  See the file configs/README.txt in the buildroot source tree.  That has more
  details PLUS some special instructions that you will need to follow if you are
  building a Cortex-M3 toolchain for Cygwin under Windows.

  NOTE:  Unfortunately, the 4.6.3 EABI toolchain is not compatible with the
  the NXFLAT tools.  See the top-level TODO file (under "Binary loaders") for
  more information about this problem. If you plan to use NXFLAT, please do not
  use the GCC 4.6.3 EABI toochain; instead use the GCC 4.3.3 OABI toolchain.
  See instructions below.

NuttX OABI "buildroot" Toolchain
================================

  The older, OABI buildroot toolchain is also available.  To use the OABI
  toolchain, use the build instructions above, but (1) modify the
  cortexm3-eabi-defconfig-4.6.3 configuration to use OABI (using 'make
  menuconfig'), or (2) use an existing OABI configuration such as
  cortexm3-defconfig-4.3.3

NXFLAT Toolchain
================

  If you are *not* using the NuttX buildroot toolchain and you want to use
  the NXFLAT tools, then you will still have to build a portion of the buildroot
  tools -- just the NXFLAT tools.  The buildroot with the NXFLAT tools can
  be downloaded from the NuttX SourceForge download site
  (https://sourceforge.net/projects/nuttx/files/).

  This GNU toolchain builds and executes in the Linux or Cygwin environment.

  1. You must have already configured Nuttx in <some-dir>/nuttx.

     cd tools
     ./configure.sh sama5d3x-ek/<sub-dir>

  2. Download the latest buildroot package into <some-dir>

  3. unpack the buildroot tarball.  The resulting directory may
     have versioning information on it like buildroot-x.y.z.  If so,
     rename <some-dir>/buildroot-x.y.z to <some-dir>/buildroot.

  4. cd <some-dir>/buildroot

  5. cp configs/cortexm3-defconfig-nxflat .config

  6. make oldconfig

  7. make

  8. Edit setenv.h, if necessary, so that the PATH variable includes
     the path to the newly built NXFLAT binaries.

Loading Code into SRAM with J-Link
==================================

  Loading code with the Segger tools and GDB
  ------------------------------------------

    1) Change directories into the directory where you built NuttX.
    2) Start the GDB server and wait until it is ready to accept GDB
       connections.
    3) Then run GDB like this:

         $ arm-none-eabi-gdb
         (gdb) target remote localhost:2331
         (gdb) mon reset
         (gdb) load nuttx
         (gdb) ... start debugging ...

  Loading code using J-Link Commander
  ----------------------------------

    J-Link> r
    J-Link> loadbin <file> <address>
    J-Link> setpc <address of __start>
    J-Link> ... start debugging ...

Writing to FLASH using SAM-BA
=============================

  Assumed starting configuration:

    1. You have installed the J-Link CDC USB driver (Windows only, there is
        no need to install a driver on any regular Linux distribution),
    2. You have the USB connected to DBGU port (J14)
    3. Terminal configuration:  115200 8N1

  Using SAM-BA to write to FLASH:

    1. Exit the terminal emulation program and remove the USB cable from
       the DBGU port (J14)
    2. Connect the USB cable to the device USB port (J20)
    3. JP9 must open (BMS == 1) to boot from on-chip Boot ROM.
    4. Press and maintain PB4 CS_BOOT button and power up the board.  PB4
       CS_BOOT button prevents booting from Nand or serial Flash by
       disabling Flash Chip Selects after having powered the board, you can
       release the PB4 BS_BOOT button.
    5. On Windows you may need to wait for a device driver to be installed.
    6. Start the SAM-BA application, selecting (1) the correct USB serial
       port, and (2) board = at91sama5d3x-ek.
    7. The SAM-BA menu should appear.
    8. Select the FLASH bank that you want to use and the address to write
       to and "Execute"
    9. When you are finished writing to FLASH, remove the USB cable from J20
       and re-connect the serial link on USB CDC / DBGU connector (J14) and
       re-open the terminal emulator program.
    10. If you loaded code in NOR flash (CS0), then you will need to close
        JP9 (BMS == 0) to force booting out of NOR flash (see NOTE).
    11. Power cycle the board.

  NOTES:  By closing JP9 (BMS == 0), you can force the board to boot
  directly to NOR FLASH.  Executing from other memories will require that
  you provide a special code header so that you code can be recognized as a
  boot-able image by the ROM bootloader.

Creating and Using NORBOOT
==========================

  In order to have more control of debugging code that runs out of NOR FLASH,
  I created the sama5d3x-ek/norboot configuration.  That configuration is
  described below under "Configurations."

  Here are some general instructions on how to build an use norboot:

  Building:
  1. Remove any old configurations (if applicable).

       cd <nuttx>
       make distclean

  2. Install and build the norboot configuration.  This steps will establish
     the norboot configuration and setup the PATH variable in order to do
     the build:

       cd tools
       ./configure.sh sama5d3x-ek/<subdir>
       cd -
       . ./setenv.sh

     Before sourcing the setenv.sh file above, you should examine it and
     perform edits as necessary so that TOOLCHAIN_BIN is the correct path
     to the directory than holds your toolchain binaries.

     NOTE:  Be aware that the default norboot also disables the watchdog.
     Since you will not be able to re-enable the watchdog later, you may
     need to set CONFIG_SAMA5_WDT=y in the NuttX configuration file.

     Then make norboot:

       make

     This will result in an ELF binary called 'nuttx' and also HEX and
     binary versions called 'nuttx.hex' and 'nuttx.bin'.

  3. Rename the binaries.  Since you will need two versions of NuttX:  this
     norboot version that runs in internal SRAM and another under test in
     NOR FLASH, I rename the resulting binary files so that they can be
     distinguished:

       mv nuttx norboot
       mv nuttx.hex norboot.hex
       mv nuttx.bin norboot.bin

  4. Build your NOR configuration and write this into NOR FLASH.  Here, for
     example, is how you would create the NSH NOR configuration:

       cd <nuttx>
       make distclean                 # Remove the norboot configuration
       cd tools
       ./configure.sh sama5d3x-ek/nsh # Establish the NSH configuration
       cd -
       make                           # Build the NSH configuration

     Then use SAM-BA to write the nuttx.bin binary into NOR FLASH.  This
     will involve holding the CS_BOOT button and power cycling to start
     the ROM loader.  The SAM-BA serial connection will be on the device
     USB port, not the debug USB port.  Follow the SAM-BA instruction to
     write the nuttx.bin binary to NOR FLASH.

   5. Restart the system without holding CS_BOOT to get back to the normal
      debug setup.

   6. Then start the J-Link GDB server and GDB.  In GDB, I do the following:

       (gdb) mon reset                # Reset and halt the CPU
       (gdb) load norboot             # Load norboot into internal SRAM
       (gdb) mon go                   # Start norboot
       (gdb) mon halt                 # Break in
       (gdb) mon reg pc = 0x10000040  # Set the PC to NOR flash entry point
       (gdb) mon go                   # And jump into NOR flash

      The norboot program can also be configured to jump directly into
      NOR FLASH without requiring the final halt and go by setting
      CONFIG_SAMA5_NOR_START=y in the NuttX configuration.  However,
      since I have been debugging the early boot sequence, the above
      sequence has been most convenient for me since it allows me to
      step into the program in NOR.

   7. An option is to use the SAM-BA tool to write the NORBOOT image into
      Serial FLASH.  Then, the system will boot from Serial FLASH by
      copying the NORBOOT image in SRAM which will run and then start the
      image in NOR FLASH automatically.  This is a very convenient usage!

      NOTES: (1) There is jumper on the CM module that must be closed to
      enable use of the AT25 Serial Flash.  (2) If using SAM-BA, make sure
      that you load the NOR boot program into the boot area via the pull-
      down menu.

    STATUS:
      2013-7-30:  I have been unable to execute these configurations from NOR
        FLASH by closing the BMS jumper (J9).  As far as I can tell, this
        jumper does nothing on my board???  So I have been using the norboot
        configuration exclusively to start the program-under-test in NOR FLASH.

Buttons and LEDs
================

  Buttons
  -------
  There are five push button switches on the SAMA5D3X-EK base board:

    1. One Reset, board reset (BP1)
    2. One Wake up, push button to bring the processor out of low power mode
      (BP2)
    3. One User momentary Push Button
    4. One Disable CS Push Button

  Only the momentary push button is controllable by software (labeled
  "PB_USER1" on the board):

    - PE27.  Pressing the switch connect PE27 to grounded.  Therefore, PE27
      must be pulled high internally.  When the button is pressed the SAMA5
      will sense "0" is on PE27.

  LEDs
  ----
  There are two LEDs on the SAMA5D3 series-CM board that can be controlled
  by software.  A  blue LED is controlled via PIO pins.  A red LED normally
  provides an indication that power is supplied to the board but can also
  be controlled via software.

    PE25.  This blue LED is pulled high and is illuminated by pulling PE25
    low.

    PE24.  The red LED is also pulled high but is driven by a transistor so
    that it is illuminated when power is applied even if PE24 is not
    configured as an output.  If PE24 is configured as an output, then the
    LCD is illuminated by a high output.

  These LEDs are not used by the board port unless CONFIG_ARCH_LEDS is
  defined.  In that case, the usage by the board port is defined in
  include/board.h and src/sam_leds.c. The LEDs are used to encode OS-related
  events as follows:

    SYMBOL                Meaning                     LED state
                                                    Blue     Red
    -------------------  -----------------------  -------- --------
    LED_STARTED          NuttX has been started     OFF      OFF
    LED_HEAPALLOCATE     Heap has been allocated    OFF      OFF
    LED_IRQSENABLED      Interrupts enabled         OFF      OFF
    LED_STACKCREATED     Idle stack created         ON       OFF
    LED_INIRQ            In an interrupt              No change
    LED_SIGNAL           In a signal handler          No change
    LED_ASSERTION        An assertion failed          No change
    LED_PANIC            The system has crashed     OFF      Blinking
    LED_IDLE             MCU is is sleep mode         Not used

  Thus if the blue LED is statically on, NuttX has successfully booted and
  is, apparently, running normally.  If the red is flashing at
  approximately 2Hz, then a fatal error has been detected and the system
  has halted.

Serial Consoles
===============

  USART1
  ------
  By default USART1 is used as the NuttX serial console in all
  configurations (unless otherwise noted).  USART1 is buffered with an
  RS-232 Transceiver (Analog Devices ADM3312EARU) and connected to the DB-9
  male socket (J8).

    USART1 Connector J8
    -------------------------------
    SAMA5 FUNCTION  NUTTX PIO
    PIO   NAME      CONFIGURATION
    ---- ---------- ---------------
    PB27 RTS1       PIO_USART1_RTS
    PB29 TXD1       PIO_USART1_TXD
    PB28 RXD1       PIO_USART1_RXD
    PB26 CTS1       PIO_USART1_CTS

    NOTE: Debug TX and RX pins also go to the ADM3312EARU, but I am
    uncertain of the functionality.

    -------------------------------
    SAMA5 FUNCTION  NUTTX PIO
    PIO   NAME      CONFIGURATION
    ---- ---------- ---------------
    PB31 DTXD       PIO_DBGU_DTXD
    PB30 DRXD       PIO_DBGU_DRXD

  Hardware UART via CDC
  ---------------------
  "J-Link-OB-ATSAM3U4C comes with an additional hardware UART that is
   accessible from a host via CDC which allows terminal communication with
   the target device. This feature is enabled only if a certain port (CDC
   disabled, PA25, pin 24 on J-Link-OB-ATSAM3U4C) is NOT connected to ground
   (open).

    - Jumper JP16 not fitted: CDC is enabled
    - Jumper JP16 fitted : CDC is disabled"

Networking
==========

  Networking support via the can be added to NSH by selecting the following
  configuration options.  The SAMA5D3x supports two different Ethernet MAC
  peripherals:  (1) The 10/100Base-T EMAC peripheral and (2) the
  10/100/1000Base-T GMAC peripheral.  Only the SAMA5D31 and SAMAD35 support
  the EMAC peripheral; Only the SAMA5D33, SAMA5D34, and SAMA5D35 support
  the GMAC perpheral!  NOTE that the SAMA5D35 supports both!

  Selecting the EMAC peripheral
  -----------------------------

  System Type
    CONFIG_ARCH_CHIP_ATSAMA5D31=y       : SAMA5D31 or SAMAD35 support EMAC
    CONFIG_ARCH_CHIP_ATSAMA5D35=y       : (others do not)

  System Type -> SAMA5 Peripheral Support
    CONFIG_SAMA5_EMAC=y                 : Enable the EMAC peripheral

  System Type -> EMAC device driver options
    CONFIG_SAMA5_EMAC_NRXBUFFERS=16     : Set aside some RS and TX buffers
    CONFIG_SAMA5_EMAC_NTXBUFFERS=4
    CONFIG_SAMA5_EMAC_PHYADDR=1         : KSZ8051 PHY is at address 1
    CONFIG_SAMA5_EMAC_AUTONEG=y         : Use autonegotiation
    CONFIG_SAMA5_EMAC_RMII=y            : Either MII or RMII interface should work
    CONFIG_SAMA5_EMAC_PHYSR=30          : Address of PHY status register on KSZ8051
    CONFIG_SAMA5_EMAC_PHYSR_ALTCONFIG=y : Needed for KSZ8051
    CONFIG_SAMA5_EMAC_PHYSR_ALTMODE=0x7 : "    " " " "     "
    CONFIG_SAMA5_EMAC_PHYSR_10HD=0x1    : "    " " " "     "
    CONFIG_SAMA5_EMAC_PHYSR_100HD=0x2   : "    " " " "     "
    CONFIG_SAMA5_EMAC_PHYSR_10FD=0x5    : "    " " " "     "
    CONFIG_SAMA5_EMAC_PHYSR_100FD=0x6   : "    " " " "     "

  PHY selection.  Later in the configuration steps, you will need to select
  the KSZ8051 PHY for EMAC (See below)

  Selecting the GMAC peripheral
  -----------------------------

  System Type
    CONFIG_ARCH_CHIP_ATSAMA5D33=y       : SAMA5D31, SAMA5D33 and SAMAD35
    CONFIG_ARCH_CHIP_ATSAMA5D34=y       : support GMAC (others do not)
    CONFIG_ARCH_CHIP_ATSAMA5D35=y       :

  System Type -> SAMA5 Peripheral Support
    CONFIG_SAMA5_GMAC=y                 : Enable the GMAC peripheral

  System Type -> GMAC device driver options
    CONFIG_SAMA5_GMAC_NRXBUFFERS=16     : Set aside some RS and TX buffers
    CONFIG_SAMA5_GMAC_NTXBUFFERS=4
    CONFIG_SAMA5_GMAC_PHYADDR=1         : KSZ8051 PHY is at address 1
    CONFIG_SAMA5_GMAC_AUTONEG=y         : Use autonegotiation

  If both EMAC and GMAC are selected, you will also need:

    CONFIG_SAMA5_GMAC_ISETH0=y          : GMAC is "eth0"; EMAC is "eth1"

  PHY selection.  Later in the configuration steps, you will need to select
  the  KSZ9021/31 PHY for GMAC (See below)

  Common configuration settings
  -----------------------------

  Networking Support
    CONFIG_NET=y                        : Enable Neworking
    CONFIG_NET_SOCKOPTS=y               : Enable socket operations
    CONFIG_NET_BUFSIZE=562              : Maximum packet size (MTD) 1518 is more standard
    CONFIG_NET_RECEIVE_WINDOW=562       : Should be the same as CONFIG_NET_BUFSIZE
    CONFIG_NET_TCP=y                    : Enable TCP/IP networking
    CONFIG_NET_TCPBACKLOG=y             : Support TCP/IP backlog
    CONFIG_NET_TCP_READAHEAD_BUFSIZE=562  Read-ahead buffer size
    CONFIG_NET_UDP=y                    : Enable UDP networking
    CONFIG_NET_ICMP=y                   : Enable ICMP networking
    CONFIG_NET_ICMP_PING=y              : Needed for NSH ping command
                                        : Defaults should be okay for other options
  Device drivers -> Network Device/PHY Support
    CONFIG_NETDEVICES=y                 : Enabled PHY selection
    CONFIG_ETH0_PHY_KSZ8051=y           : Select the KSZ8051 PHY (for EMAC), OR
    CONFIG_ETH0_PHY_KSZ90x1=y           : Select teh KSZ9021/31 PHY (for GMAC)

  Application Configuration -> Network Utilities
    CONFIG_NETUTILS_RESOLV=y            : Enable host address resolution
    CONFIG_NETUTILS_TELNETD=y           : Enable the Telnet daemon
    CONFIG_NETUTILS_TFTPC=y             : Enable TFTP data file transfers for get and put commands
    CONFIG_NETUTILS_UIPLIB=y            : Network library support is needed
    CONFIG_NETUTILS_WEBCLIENT=y         : Needed for wget support
                                        : Defaults should be okay for other options
  Application Configuration -> NSH Library
    CONFIG_NSH_TELNET=y                 : Enable NSH session via Telnet
    CONFIG_NSH_IPADDR=0x0a000002        : Select an IP address
    CONFIG_NSH_DRIPADDR=0x0a000001      : IP address of gateway/host PC
    CONFIG_NSH_NETMASK=0xffffff00       : Netmask
    CONFIG_NSH_NOMAC=y                  : Need to make up a bogus MAC address
                                        : Defaults should be okay for other options

  Using the network with NSH
  --------------------------

  So what can you do with this networking support?  First you see that
  NSH has several new network related commands:

    ifconfig, ifdown, ifup:  Commands to help manage your network
    get and put:             TFTP file transfers
    wget:                    HTML file transfers
    ping:                    Check for access to peers on the network
    Telnet console:          You can access the NSH remotely via telnet.

  You can also enable other add on features like full FTP or a Web
  Server or XML RPC and others.  There are also other features that
  you can enable like DHCP client (or server) or network name
  resolution.

  By default, the IP address of the SAMA5D3x-EK will be 10.0.0.2 and
  it will assume that your host is the gateway and has the IP address
  10.0.0.1.

    nsh> ifconfig
    eth0    HWaddr 00:e0:de:ad:be:ef at UP
            IPaddr:10.0.0.2 DRaddr:10.0.0.1 Mask:255.255.255.0

  You can use ping to test for connectivity to the host (Careful,
  Window firewalls usually block ping-related ICMP traffic).  On the
  target side, you can:

    nsh> ping 10.0.0.1
    PING 10.0.0.1 56 bytes of data
    56 bytes from 10.0.0.1: icmp_seq=1 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=2 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=3 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=4 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=5 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=6 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=7 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=8 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=9 time=0 ms
    56 bytes from 10.0.0.1: icmp_seq=10 time=0 ms
    10 packets transmitted, 10 received, 0% packet loss, time 10100 ms

  NOTE: In this configuration is is normal to have packet loss > 0%
  the first time you ping due to the default handling of the ARP
  table.

  On the host side, you should also be able to ping the SAMA5D3-EK:

    $ ping 10.0.0.2

  You can also log into the NSH from the host PC like this:

    $ telnet 10.0.0.2
    Trying 10.0.0.2...
    Connected to 10.0.0.2.
    Escape character is '^]'.
    sh_telnetmain: Session [3] Started

    NuttShell (NSH) NuttX-6.31
    nsh> help
    help usage:  help [-v] [<cmd>]

      [           echo        ifconfig    mkdir       mw          sleep
      ?           exec        ifdown      mkfatfs     ping        test
      cat         exit        ifup        mkfifo      ps          umount
      cp          free        kill        mkrd        put         usleep
      cmp         get         losetup     mh          rm          wget
      dd          help        ls          mount       rmdir       xd
      df          hexdump     mb          mv          sh

    Builtin Apps:
    nsh>

  NOTE:  If you enable this feature, you experience a delay on booting.
  That is because the start-up logic waits for the network connection
  to be established before starting NuttX.  In a real application, you
  would probably want to do the network bringup on a separate thread
  so that access to the NSH prompt is not delayed.

  This delay will be especially long if the board is not connected to
  a network.

AT25 Serial FLASH
=================

  Connections
  -----------

  Both the Ronetix and Embest versions of the SAMAD3x CPU modules include an
  Atmel AT25DF321A, 32-megabit, 2.7-volt SPI serial flash.  The SPI
  connection is as follows:

    AT25DF321A      SAMA5
    --------------- -----------------------------------------------
    SI              PD11 SPI0_MOSI
    SO              PD10 SPI0_MIS0
    SCK             PD12 SPI0_SPCK
    /CS             PD13 via NL17SZ126 if JP1 is closed (See below)

  JP1 and JP2 seem to related to /CS on the Ronetix board, but the usage is
  less clear.  For the Embest module, JP1 must be closed to connect /CS to
  PD13; on the Ronetix schematic, JP11 seems only to bypass a resistor (may
  not be populated?).  I think closing JP1 is correct in either case.

  Configuration
  -------------

  The Embest or Ronetix CPU module includes an Atmel AT25DF321A, 32-megabit,
  2.7-volt SPI serial flash.  Support for that serial FLASH can be enabled
  in these configurations.  These are the relevant  configuration settings:

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_SPI0=y                   : Enable SPI0
      CONFIG_SAMA5_DMAC0=y                  : Enable DMA controller 0

    System Type -> SPI device driver options
      CONFIG_SAMA5_SPI_DMA=y                : Use DMA for SPI transfers
      CONFIG_SAMA5_SPI_DMATHRESHOLD=4       : Don't DMA for small transfers

    Device Drivers -> SPI Driver Support
      CONFIG_SPI=y                          : Enable SPI support
      CONFIG_SPI_EXCHANGE=y                 : Support the exchange method

    Device Drivers -> Memory Technology Device (MTD) Support
      CONFIG_MTD=y                          : Enable MTD support
      CONFIG_MTD_AT25=y                     : Enable the AT25 driver
      CONFIG_AT25_SPIMODE=0                 : Use SPI mode 0
      CONFIG_AT25_SPIFREQUENCY=10000000     : Use SPI frequency 10MHz

  The AT25 is capable of higher SPI rates than this.  I have not experimented
  a lot, but at 20MHz, the behavior is not the same with all CM modules.  This
  lower rate gives more predictable performance.

    Application Configuration -> NSH Library
      CONFIG_NSH_ARCHINIT=y                 : NSH board-initialization

    Board Selection
      CONFIG_SAMA5_AT25_AUTOMOUNT=y         : Mounts AT25 for NSH
      CONFIG_SAMA5_AT25_FTL=y               : Create block driver for FAT

  NOTE that you must close JP1 on the Embest/Ronetix board in order to
  enable the AT25 FLASH chip select.

  You can then format the AT25 FLASH for a FAT file system and mount the
  file system at /mnt/at25 using these NSH commands:

    nsh> mkfatfs /dev/mtdblock0
    nsh> mount -t vfat /dev/mtdblock0 /mnt/at25

  Then you an use the FLASH as a normal FAT file system:

    nsh> echo "This is a test" >/mnt/at25/atest.txt
    nsh> ls -l /mnt/at25
    /mnt/at25:
     -rw-rw-rw-      16 atest.txt
    nsh> cat /mnt/at25/atest.txt
    This is a test

  NOTE:  It appears that if Linux runs out of NAND, it will destroy the
  contents of the AT25.

HSMCI Card Slots
================

  Physical Slots
  --------------

  The SAMA5D3x-EK provides a two SD memory card slots:  (1) a full size SD
  card slot (J7 labelled MCI0), and (2) a microSD memory card slot (J6
  labelled MCI1).

  The full size SD card slot connects via HSMCI0.  The card detect discrete
  is available on PB17 (pulled high).  The write protect discrete is tied to
  ground (via PP6) and not available to software.  The slot supports 8-bit
  wide transfer mode, but the NuttX driver currently uses only the 4-bit
  wide transfer mode

    PD17 MCI0_CD
    PD1  MCI0_DA0
    PD2  MCI0_DA1
    PD3  MCI0_DA2
    PD4  MCI0_DA3
    PD5  MCI0_DA4
    PD6  MCI0_DA5
    PD7  MCI0_DA6
    PD8  MCI0_DA7
    PD9  MCI0_CK
    PD0  MCI0_CDA

  The microSD connects vi HSMCI1.  The card detect discrete is available on
  PB18 (pulled high):

    PD18  MCI1_CD
    PB20  MCI1_DA0
    PB21  MCI1_DA1
    PB22  MCI1_DA2
    PB23  MCI1_DA3
    PB24  MCI1_CK
    PB19  MCI1_CDA

  Configuration Settings
  ----------------------

  Enabling HSMCI support. The SAMA5D3x-EK provides a two SD memory card
  slots:  (1) a full size SD card slot (J7 labelled MCI0), and (2) a
  microSD memory card slot (J6 labelled MCI1).  The full size SD card slot
  connects via HSMCI0; the microSD connects vi HSMCI1.  Support for both SD
  slots can be enabled with the following settings:

    System Type->ATSAMA5 Peripheral Support
      CONFIG_SAMA5_HSMCI0=y                 : Enable HSMCI0 support
      CONFIG_SAMA5_HSMCI1=y                 : Enable HSMCI1 support
      CONFIG_SAMA5_DMAC0=y                  : DMAC0 is needed by HSMCI0
      CONFIG_SAMA5_DMAC1=y                  : DMAC1 is needed by HSMCI1

    System Type
      CONFIG_SAMA5_PIO_IRQ=y                : PIO interrupts needed
      CONFIG_SAMA5_PIOD_IRQ=y               : Card detect pins are on PIOD

    Device Drivers -> MMC/SD Driver Support
      CONFIG_MMCSD=y                        : Enable MMC/SD support
      CONFIG_MMSCD_NSLOTS=1                 : One slot per driver instance
      CONFIG_MMCSD_HAVECARDDETECT=y         : Supports card-detect PIOs
      CONFIG_MMCSD_MMCSUPPORT=n             : Interferes with some SD cards
      CONFIG_MMCSD_SPI=n                    : No SPI-based MMC/SD support
      CONFIG_MMCSD_SDIO=y                   : SDIO-based MMC/SD support
      CONFIG_SDIO_DMA=y                     : Use SDIO DMA
      CONFIG_SDIO_BLOCKSETUP=y              : Needs to know block sizes

    Library Routines
      CONFIG_SCHED_WORKQUEUE=y              : Driver needs work queue support

    Application Configuration -> NSH Library
      CONFIG_NSH_ARCHINIT=y                 : NSH board-initialization

    Using the SD card
    -----------------

    1) After booting, the HSCMI devices will appear as /dev/mmcsd0
       and /dev/mmcsd1.

    2) If you try mounting an SD card with nothing in the slot, the
       mount will fail:

         nsh> mount -t vfat /dev/mmcsd1 /mnt/sd1
         nsh: mount: mount failed: 19

       NSH can be configured to provide errors as strings instead of
       numbers.  But in this case, only the error number is reported.  The
       error numbers can be found in nuttx/include/errno.h:

         #define ENODEV              19
         #define ENODEV_STR          "No such device"

       So the mount command is saying that there is no device or, more
       correctly, that there is no card in the SD card slot.

    3) Inserted the SD card.  Then the mount should succeed.

        nsh> mount -t vfat /dev/mmcsd1 /mnt/sd1
        nsh> ls /mnt/sd1
        /mnt/sd1:
         atest.txt
        nsh> cat /mnt/sd1/atest.txt
        This is a test

    4) Before removing the card, you must umount the file system.  This is
       equivalent to "ejecting" or "safely removing" the card on Windows:  It
       flushes any cached data to the card and makes the SD card unavailable
       to the applications.

         nsh> umount -t /mnt/sd1

       It is now safe to remove the card.  NuttX provides into callbacks
       that can be used by an application to automatically unmount the
       volume when it is removed.  But those callbacks are not used in
       these configurations.

USB Ports
=========

  The SAMA5D3 series-MB features three USB communication ports:

    * Port A Host High Speed (EHCI) and Full Speed (OHCI) multiplexed with
      USB Device High Speed Micro AB connector, J20

    * Port B Host High Speed (EHCI) and Full Speed (OHCI) standard type A
      connector, J19 upper port

    * Port C Host Full Speed (OHCI) only standard type A connector, J19
      lower port

  All three USB host ports are equipped with 500 mA high-side power switch
  for self-powered and bus powered applications. The USB device port feature
  VBUS inserts detection function.

  Port A
  ------

    PIO  Signal Name Function
    ---- ----------- -------------------------------------------------------
    PD29  VBUS_SENSE VBus detection
    PD25  EN5V_USBA  VBus power enable (via MN15 AIC1526 Dual USB High-Side
                     Power Switch.  The other channel of the switch is for
                     the LCD)

  Port B
  ------

    PIO  Signal Name Function
    ---- ----------- -------------------------------------------------------
    PD26 EN5V_USBB   VBus power enable (via MN14 AIC1526 Dual USB High-Side
                     Power Switch).  To the A1 pin of J19 Dual USB A
                     connector

  Port C
  ------

    PIO  Signal Name Function
    ---- ----------- -------------------------------------------------------
    PD27 EN5V_USBC   VBus power enable (via MN14 AIC1526 Dual USB High-Side
                     Power Switch).  To the B1 pin of J19 Dual USB A
                     connector

  Both Ports B and C
  ------------------

    PIO  Signal Name Function
    ---- ----------- -------------------------------------------------------
    PD28 OVCUR_USB   Combined overrcurrent indication from port A and B

USB High-Speed Device
=====================

  Basic USB High-Speed Device Configuration
  -----------------------------------------

  Support the USB high-speed device (UDPHS) driver can be enabled with these
  NuttX configuration settings.

    Device Drivers -> USB Device Driver Support
      CONFIG_USBDEV=y                       : Enable USB device support
      CONFIG_USBDEV_DUALSPEED=y             : Device support High and Full Speed
      CONFIG_USBDEV_DMA=y                   : Device uses DMA

    System Type -> ATSAMA5 Peripheral Support
      CONFIG_SAMA5_UDPHS=y                  : Enable UDPHS High Speed USB device

    Application Configuration -> NSH Library
      CONFIG_NSH_ARCHINIT=y                 : NSH board-initialization

  Mass Storage Class
  ------------------

  The Mass Storage Class (MSC) class driver is selected for use with
  UDPHS:

    Device Drivers -> USB Device Driver Support
      CONFIG_USBMSC=y                       : Enable the USB MSC class driver
      CONFIG_USBMSC_EPBULKOUT=1             : Use EP1 for the BULK OUT endpoint
      CONFIG_USBMSC_EPBULKIN=2              : Use EP2 for the BULK IN endpoint

  The following setting enables an add-on that can can be used to control
  the USB MSC device.  It will add two new NSH commands:

    a. msconn will connect the USB serial device and export the AT25
       to the host, and
    b. msdis which will disconnect the USB serial device.

    Application Configuration -> System Add-Ons:
      CONFIG_SYSTEM_USBMSC=y                : Enable the USBMSC add-on
      CONFIG_SYSTEM_USBMSC_NLUNS=1          : One LUN
      CONFIG_SYSTEM_USBMSC_DEVMINOR1=0      : Minor device zero
      CONFIG_SYSTEM_USBMSC_DEVPATH1="/dev/mtdblock0"
                                            : Use a single, LUN:  The AT25
                                            : block driver.

    NOTES:

    a. To prevent file system corruption, make sure that the AT25 is un-
       mounted *before* exporting the mass storage device to the host:

         nsh> umount /mnt/at25
         nsh> mscon

       The AT25 can be re-mounted after the mass storage class is disconnected:

        nsh> msdis
        nsh> mount -t vfat /dev/mtdblock0 /mnt/at25

    b. If you change the value CONFIG_SYSTEM_USBMSC_DEVPATH1, then you
       can export other file systems:

        "/dev/mmcsd1" will export the HSMCI1 microSD
        "/dev/mmcsd0" will export the HSMCI0 full-size SD slot
        "/dev/ram0" could even be used to export a RAM disk.  But you would
          first have to use mkrd to create the RAM disk and mkfatfs to put
          a FAT file system on it.

  CDC/ACM Serial Device Class
  ---------------------------

  This will select the CDC/ACM serial device.  Defaults for the other
  options should be okay.

    Device Drivers -> USB Device Driver Support
      CONFIG_CDCACM=y                       : Enable the CDC/ACM device
      CONFIG_CDCACM_BULKIN_REQLEN=768       : Default too small for high-speed

  The following setting enables an example that can can be used to control
  the CDC/ACM device.  It will add two new NSH commands:

    a. sercon will connect the USB serial device (creating /dev/ttyACM0), and
    b. serdis which will disconnect the USB serial device (destroying
        /dev/ttyACM0).

    Application Configuration -> Examples:
      CONFIG_SYSTEM_CDCACM=y              : Enable an CDC/ACM example

  Debugging USB Device
  --------------------

  There is normal console debug output available that can be enabled with
  CONFIG_DEBUG + CONFIG_DEBUG_USB.  However, USB device operation is very
  time critical and enabling this debug output WILL interfere with the
  operation of the UDPHS.  USB device tracing is a less invasive way to get
  debug information:  If tracing is enabled, the USB device will save
  encoded trace output in in-memory buffer; if the USB monitor is also
  enabled, that trace buffer will be periodically emptied and dumped to the
  system logging device (the serial console in this configuration):

    Device Drivers -> "USB Device Driver Support:
      CONFIG_USBDEV_TRACE=y                   : Enable USB trace feature
      CONFIG_USBDEV_TRACE_NRECORDS=256        : Buffer 256 records in memory
      CONFIG_USBDEV_TRACE_STRINGS=y           : (optional)

    Application Configuration -> NSH LIbrary:
      CONFIG_NSH_USBDEV_TRACE=n               : No builtin tracing from NSH
      CONFIG_NSH_ARCHINIT=y                   : Automatically start the USB monitor

    Application Configuration -> System NSH Add-Ons:
      CONFIG_SYSTEM_USBMONITOR=y              : Enable the USB monitor daemon
      CONFIG_SYSTEM_USBMONITOR_STACKSIZE=2048 : USB monitor daemon stack size
      CONFIG_SYSTEM_USBMONITOR_PRIORITY=50    : USB monitor daemon priority
      CONFIG_SYSTEM_USBMONITOR_INTERVAL=1     : Dump trace data every second
      CONFIG_SYSTEM_USBMONITOR_TRACEINIT=y    : Enable TRACE output
      CONFIG_SYSTEM_USBMONITOR_TRACECLASS=y
      CONFIG_SYSTEM_USBMONITOR_TRACETRANSFERS=y
      CONFIG_SYSTEM_USBMONITOR_TRACECONTROLLER=y
      CONFIG_SYSTEM_USBMONITOR_TRACEINTERRUPTS=y

  NOTE: If USB debug output is also enabled, both outputs will appear on the
  serial console.  However, the debug output will be asynchronous with the
  trace output and, hence, difficult to interpret.

USB High-Speed Host
===================

  OHCI Only
  ---------

  Support the USB low/full-speed OHCI host driver can be enabled by changing
  the NuttX configuration file as follows:

    System Type -> ATSAMA5 Peripheral Support
      CONFIG_SAMA5_UHPHS=y                 : USB Host High Speed

    System Type -> USB High Speed Host driver options
      CONFIG_SAMA5_OHCI=y                  : Low/full-speed OHCI support
                                           : Defaults for values probably OK
    Device Drivers
      CONFIG_USBHOST=y                     : Enable USB host support

    Device Drivers -> USB Host Driver Support
      CONFIG_USBHOST_ISOC_DISABLE=y        : Isochronous endpoints not used
      CONFIG_USBHOST_MSC=y                 : Enable the mass storage class driver
      CONFIG_USBHOST_HIDKBD=y              : Enable the HID keyboard class driver

    Library Routines
      CONFIG_SCHED_WORKQUEUE=y             : Worker thread support is required

    Application Configuration -> NSH Library
      CONFIG_NSH_ARCHINIT=y                 : NSH board-initialization

  NOTE:  When OHCI is selected, the SAMA5 will operate at 384MHz instead of
  396MHz.  This is so that the PLL generates a frequency which is a multiple
  of the 48MHz needed for OHCI.  The delay loop calibration values that are
  used will be off slightly because of this.

  EHCI
  ----

  Support the USB high-speed EHCI host driver can be enabled by changing the
  NuttX configuration file as follows.  If EHCI is enabled by itself, then
  only high-speed devices can be supported.  If OHCI is also enabled, then
  all low-, full-, and high speed devices will work.

    System Type -> ATSAMA5 Peripheral Support
      CONFIG_SAMA5_UHPHS=y                 : USB Host High Speed

    System Type -> USB High Speed Host driver options
      CONFIG_SAMA5_EHCI=y                  : High-speed EHCI support
      CONFIG_SAMA5_OHCI=y                  : Low/full-speed OHCI support
                                               : Defaults for values probably OK for both
    Device Drivers
      CONFIG_USBHOST=y                     : Enable USB host support
      CONFIG_USBHOST_INT_DISABLE=y         : Interrupt endpoints not needed
      CONFIG_USBHOST_ISOC_DISABLE=y        : Isochronous endpoints not needed

    Device Drivers -> USB Host Driver Support
      CONFIG_USBHOST_ISOC_DISABLE=y        : Isochronous endpoints not used
      CONFIG_USBHOST_MSC=y                 : Enable the mass storage class driver
      CONFIG_USBHOST_HIDKBD=y              : Enable the HID keyboard class driver

    Library Routines
      CONFIG_SCHED_WORKQUEUE=y             : Worker thread support is required

    Application Configuration -> NSH Library
      CONFIG_NSH_ARCHINIT=y                 : NSH board-initialization

  Mass Storage Device Usage
  -------------------------

  Example Usage:

    NuttShell (NSH) NuttX-6.29
    nsh> ls /dev
     /dev:
     console
     mtdblock0
     null
     ttyS0

  Here a USB FLASH stick is inserted.  Nothing visible happens in the
  shell.  But a new device will appear:

    nsh> ls /dev
    /dev:
     console
     mtdblock0
     null
     sda
     ttyS0
    nsh> mount -t vfat /dev/sda /mnt/sda
    nsh> ls -l /mnt/sda
    /mnt/sda:
     -rw-rw-rw-    8788 viminfo
     drw-rw-rw-       0 .Trash-1000/
     -rw-rw-rw-    3378 zmodem.patch
     -rw-rw-rw-    1503 sz-1.log
     -rw-rw-rw-     613 .bashrc

  HID Keyboard Usage
  ------------------

  If a (supported) USB keyboard is connected, a /dev/kbda device will appear:

    nsh> ls /dev
    /dev:
     console
     kbda
     mtdblock0
     null
     ttyS0

  /dev/kbda is a read-only serial device.  Reading from /dev/kbda will get
  keyboard input as ASCII data (other encodings are possible):

    nsh> cat /dev/kbda

  Debugging USB Host
  ------------------

  There is normal console debug output available that can be enabled with
  CONFIG_DEBUG + CONFIG_DEBUG_USB.  However, USB host operation is very time
  critical and enabling this debug output might interfere with the operation
  of the UDPHS.  USB host tracing is a less invasive way to get debug
  information:  If tracing is enabled, the USB host will save encoded trace
  output in in-memory buffer; if the USB monitor is also enabled, that trace
  buffer will be periodically emptied and dumped to the system logging device
  (the serial console in this configuration):

    Device Drivers -> "USB Host Driver Support:
      CONFIG_USBHOST_TRACE=y                   : Enable USB host trace feature
      CONFIG_USBHOST_TRACE_NRECORDS=256        : Buffer 256 records in memory
      CONFIG_USBHOST_TRACE_VERBOSE=y           : Buffer everything

    Application Configuration -> NSH LIbrary:
      CONFIG_NSH_USBDEV_TRACE=n               : No builtin tracing from NSH
      CONFIG_NSH_ARCHINIT=y                   : Automatically start the USB monitor

    Application Configuration -> System NSH Add-Ons:
      CONFIG_SYSTEM_USBMONITOR=y              : Enable the USB monitor daemon
      CONFIG_SYSTEM_USBMONITOR_STACKSIZE=2048 : USB monitor daemon stack size
      CONFIG_SYSTEM_USBMONITOR_PRIORITY=50    : USB monitor daemon priority
      CONFIG_SYSTEM_USBMONITOR_INTERVAL=1     : Dump trace data every second

  NOTE: If USB debug output is also enabled, both outpus will appear on the
  serial console.  However, the debug output will be asynchronous with the
  trace output and, hence, difficult to interpret.

NOR FLASH Support
=================

  Most of these configurations execute out of CS0 NOR flash and can only be
  loaded via SAM-BA.  These are the relevant configuration options the
  define the NOR FLASH configuration:

    CONFIG_SAMA5_BOOT_CS0FLASH=y            : Boot from FLASH on CS0
    CONFIG_BOOT_RUNFROMFLASH=y              : Run in place on FLASH (vs copying to RAM)

    CONFIG_SAMA5_EBICS0=y                   : Enable CS0 external memory
    CONFIG_SAMA5_EBICS0_SIZE=134217728      : Memory size is 128KB
    CONFIG_SAMA5_EBICS0_NOR=y               : Memory type is NOR FLASH

    CONFIG_FLASH_START=0x10000000           : Physical FLASH start address
    CONFIG_FLASH_VSTART=0x10000000          : Virtual FLASH start address
    CONFIG_FLASH_SIZE=134217728             : FLASH size (again)

    CONFIG_RAM_START=0x00300400             : Data stored after page table
    CONFIG_RAM_VSTART=0x00300400
    CONFIG_RAM_SIZE=114688                  : Available size of 128KB - 16KB for page table

  NOTE:  In order to boot in this configuration, you need to close the BMS
  jumper.

  STATUS:  I have been unable to execute these configurations from NOR FLASH
  by closing the BMS jumper (J9).  As far as I can tell, this jumper does
  nothing on my board???  So I have been using the norboot configuration
  exclusively to start the program-under-test in NOR FLASH (see the section
  entitled "Creating and Using NORBOOT" above.)

SDRAM Support
=============

  SRAM Heap Configuration
  -----------------------

  In these configurations, .data and .bss are retained in ISRAM.  SDRAM can
  be initialized and included in the heap.  Relevant configuration settings:

    System Type->ATSAMA5 Peripheral Support
      CONFIG_SAMA5_MPDDRC=y                 : Enable the DDR controller

    System Type->External Memory Configuration
      CONFIG_SAMA5_DDRCS=y                  : Tell the system that DRAM is at the DDR CS
      CONFIG_SAMA5_DDRCS_SIZE=268435456     : 2Gb DRAM -> 256GB
      CONFIG_SAMA5_DDRCS_LPDDR2=y           : Its DDR2
      CONFIG_SAMA5_MT47H128M16RT=y          : This is the type of DDR2

    System Type->Heap Configuration
      CONFIG_SAMA5_DDRCS_HEAP=y             : Add the SDRAM to the heap
      CONFIG_SAMA5_DDRCS_HEAP_OFFSET=0
      CONFIG_SAMA5_DDRCS_HEAP_SIZE=268435456

    Memory Management
      CONFIG_MM_REGIONS=2                   : Two heap memory regions:  ISRAM and SDRAM

  RAM Test
  --------

  Another thing you could do is to enable the RAM test built-in application.
  You can enable the NuttX RAM test that may be used to verify the external
  SDRAM.  To do this, keep the SDRAM out of the heap so that it can be tested
  without crashing programs using the memory:

    System Type->Heap Configuration
      CONFIG_SAMA5_DDRCS_HEAP=n             : Don't add the SDRAM to the heap

    Memory Management
      CONFIG_MM_REGIONS=1                   : One memory regions:  ISRAM

  Then enable the RAM test built-in application:

    Application Configuration->System NSH Add-Ons->Ram Test
      CONFIG_SYSTEM_RAMTEST=y

  In this configuration, the SDRAM is not added to heap and so is not
  accessable to the applications.  So the RAM test can be freely executed
  against the SRAM memory beginning at address 0x2000:0000 (DDR CS):

    nsh> ramtest -h
    Usage: <noname> [-w|h|b] <hex-address> <decimal-size>

    Where:
      <hex-address> starting address of the test.
      <decimal-size> number of memory locations (in bytes).
      -w Sets the width of a memory location to 32-bits.
      -h Sets the width of a memory location to 16-bits (default).
      -b Sets the width of a memory location to 8-bits.

    To test the entire external 256MB SRAM:

    nsh> ramtest -w 20000000 268435456
    RAMTest: Marching ones: 20000000 268435456
    RAMTest: Marching zeroes: 20000000 268435456
    RAMTest: Pattern test: 20000000 268435456 55555555 aaaaaaaa
    RAMTest: Pattern test: 20000000 268435456 66666666 99999999
    RAMTest: Pattern test: 20000000 268435456 33333333 cccccccc
    RAMTest: Address-in-address test: 20000000 268435456

  SDRAM Data Configuration
  ------------------------
 
  In these configurations, .data and .bss are retained in ISRAM by default.
  .data and .bss can also be retained in SDRAM using these slightly
  different configuration settings.  In this configuration, ISRAM is
  used only for the Cortex-A5 page table for the IDLE thread stack.

    System Type->ATSAMA5 Peripheral Support
      CONFIG_SAMA5_MPDDRC=y                 : Enable the DDR controller

    System Type->External Memory Configuration
      CONFIG_SAMA5_DDRCS=y                  : Tell the system that DRAM is at the DDR CS
      CONFIG_SAMA5_DDRCS_SIZE=268435456     : 2Gb DRAM -> 256GB
      CONFIG_SAMA5_DDRCS_LPDDR2=y           : Its DDR2
      CONFIG_SAMA5_MT47H128M16RT=y          : This is the type of DDR2

    System Type->Heap Configuration
      CONFIG_SAMA5_ISRAM_HEAP=n              : These do not apply in this case
      CONFIG_SAMA5_DCRS_HEAP=n

    System Type->Boot Memory Configuration
      CONFIG_RAM_START=0x20000000           : Physical address of SDRAM
      CONFIG_RAM_VSTART=0x20000000          : Virtual address of SDRAM
      CONFIG_RAM_SIZE=268435456             : Size of SDRAM
      CONFIG_BOOT_SDRAM_DATA=y              : Data is in SDRAM

      Care must be used applied these RAM locations; the graphics
      configurations use SDRAM in an incompatible way to set aside
      LCD framebuffers.

    Memory Management
      CONFIG_MM_REGIONS=1                   : One heap memory region:  ISDRAM

NAND Support
============

  NAND support is only partial in that there is no file system that works
  with it properly.  Lower-level NAND support has been developed and
  verified, but there is no way to use it in the current NuttX architecture
  other than through the raw MTD interface.

  NAND should still be considered a work in progress.  You will not want to
  use NAND unless you are interested in investing a little effort,
  particularly in infrastructure. See the "STATUS SUMMARY" section below.

  NAND Support
  ------------

  NAND Support can be added to the NSH configuration by modifying the
  NuttX configuration file as follows:

    Build Setup
      CONFIG_EXPERIMENTAL=y             : NXFFS implementation is incomplete and
                                        : not yet fully functional.

    System Type -> SAMA5 Peripheral support
      CONFIG_SAMA5_HSMC=y               : Make sure that the SMC is enabled

    Drivers -> Memory Technology Device (MTD) Support
      CONFIG_MTD=y                      : Enable MTD support
      CONFIG_MTD_NAND=y                 : Enable NAND support
      CONFIG_MTD_NAND_BLOCKCHECK=n      : Interferes with NXFFS bad block checking
      CONFIG_MTD_NAND_SWECC=y           : Use S/W ECC calculation

      Defaults for all other NAND settings should be okay

    System Type -> External Memory Configuration
      CONFIG_SAMA5_EBICS3=y             : Enable External CS3 memory
      CONFIG_SAMA5_EBICS3_NAND=y        : Select NAND memory type
      CONFIG_SAMA5_EBICS3_SIZE=8388608  : Use this size
      CONFIG_SAMA5_EBICS3_SWECC=y       : Use S/W ECC calculation

      Defaults for ROM page table addresses should be okay

    Application Configuration -> NSH Library
      CONFIG_NSH_ARCHINIT=y             : Use architecture-specific initialization

    NOTES:

    1. WARNING:  This will wipe out everything that you may have on the NAND
       FLASH!  I have found that using the JTAG with no valid image on NAND
       or Serial FLASH is a problem:  In that case, the code always ends up
       in the SAM-BA bootloader.

       My understanding is that you can enable JTAG in this case by simply
       entering any data on the DBG serial port.  I have not tried this.
       Instead, I just changed to boot from Serial Flash:

    2. Booting from Serial Flash. The work around for this case is to put
       the NORBOOT image into Serial FLASH.  Then, the system will boot from
       Serial FLASH by copying the NORBOOT image in SRAM which will run and
       then start the image in NOR FLASH.  See the discussion of the NORBOOT
       configuration in the "Creating and Using NORBOOT" section above.

       NOTE that there is jumper on the CM module that must be closed to enable
       use of the AT25 Serial Flash.  Also, if you are using using SAM-BA,
       make sure that you load the NOR boot program into the boot area via
       the pull-down menu.

    3. Unfortunately, there are no appropriate NAND file system in NuttX as
       of this writing.  The following sections discussion issues/problems
       with using NXFFS and FAT.

    PMECC
    -----

    Hardware ECC calculation using the SAMA5D3's PMECC can be enable as
    follows:

    Drivers -> Memory Technology Device (MTD) Support
      CONFIG_MTD_NAND_SWECC=y           : Don't use S/W ECC calculation
      CONFIG_MTD_NAND_HWECC=y           : Use H/W ECC instead

    System Type -> External Memory Configuration
      CONFIG_SAMA5_EBICS3_SWECC=n       : Don't use S/W ECC calculation
      CONFIG_SAMA5_HAVE_PMECC=n         : Use H/W ECC instead

    Other PMECC-related default settings should be okay.

    STATUS:  As of the writing, NAND transfers using PMECC appear to
    work correctly.  However, the PMECC based systems do not work as
    as well with FAT or NXFFS.  My belief that that the FAT/NXFFS layers
    are inappropriate for NAND and, as a result, happen not to work with
    the PMECC ECC calculation.  See also the "STATUS SUMMARY" section below.

    DMA Support
    -----------

    DMA support can be enabled as follows:

    System Type -> SAMA5 Peripheral support
      CONFIG_SAMA5_DMAC0=y              : Use DMAC0 for memory-to-memory DMA

    System Type -> External Memory Configuration
      CONFIG_SAMA5_NAND_DMA=y           : Use DMAC0 for NAND data transfers

    STATUS:  DMA appears to be functional, but probably has not been
    exercised enough to claim that with any certainty.  See also the "STATUS
    SUMMARY" section below.

    NXFFS
    -----

    The NuttX FLASH File System (NXFFS) works well with NOR-like FLASH
    but does not work well with NAND (See comments below under STATUS)

    File Systems:
      CONFIG_FS_NXFFS=y                 : Enable the NXFFS file system

      Defaults for all other NXFFS settings should be okay.

      NOTE:  NXFFS will require some significant buffering because of
      the large size of the NAND flash blocks.  You will also need
      to enable SDRAM as described above.

    Board Selection
      CONFIG_SAMA5_NAND_AUTOMOUNT=y     : Enable FS support on NAND
      CONFIG_SAMA5_NAND_NXFFS=y         : Use the NXFFS file system

      Other file systems are not recommended because only NXFFS can handle
      bad blocks and only NXFFS performs wear-levelling.

    FAT
    ---

    Another option is FAT.  FAT, however, is not appropriate for use with
    NAND: FAT will not handle bad blocks, does not perform any wear
    levelling, and may not conform to writing ordering requirements of NAND.
    Also, there appear to be issues with FAT when PMECC is enabled (see
    "STATUS SUMMARY" below).

    File Systems:
      CONFIG_FS_FAT=y                   : Enable the FAT FS
      CONFIG_FAT_LCNAMES=y              : With lower case name support
      CONFIG_FAT_LFN=y                  : And (patented) FAT long file name support
      CONFIG_FS_NXFFS=n                 : Don't need NXFFS

      Defaults for all other NXFFS settings should be okay.

    Board Selection
      CONFIG_SAMA5_NAND_AUTOMOUNT=y     : Enable FS support on NAND
      CONFIG_SAMA5_NAND_FTL=y           : Use an flash translation layer

      NOTE:  FTL will require some significant buffering because of
      the large size of the NAND flash blocks.  You will also need
      to enable SDRAM as described above.

    SMART FS
    --------

    Another option is Smart FS.  Smart FS is another small file system
    designed to work with FLASH.  Properties:  It does support some wear-
    leveling like NXFFS, but like FAT, cannot handle bad blocks and like
    NXFFS, it will try to re-write erased bits.

    Using NAND with NXFFS
    ---------------------

    With the options CONFIG_SAMA5_NAND_AUTOMOUNT=y and
    CONFIG_SAMA5_NAND_NXFFS=y, the NAND FLASH will be mounted in the NSH
    start-up logic before the NSH prompt appears.  There is no feedback as
    to whether or not the mount was successful.  You can, however, see the
    mounted file systems using the nsh 'mount' command:

      nsh> mount
      /mnt/nand type nxffs

    Then NAND can be used like any other file system:

      nsh> echo "This is a test" >/mnt/nand/atest.txt
      nsh> ls -l /mnt/nand
      /mnt/nand:
       ---x--x--x      16 atest.txt
      nsh> cat /mnt/nand/atest.txt
      This is a test

    The NAND volume can be un-mounted with this comment:

      nsh> umount /mnt/nand
      nsh> mount

    And re-mounted with this command:

      nsh> mount -t nxffs /mnt/mystuff
      nsh> mount
        /mnt/mystuff type nxffs

    NOTES:
      1. NXFFS can be very slow.  The first time that you start the system,
         be prepared for a wait; NXFFS will need to format the NAND volume.
         I have lots of debug on so I don't yet know what the optimized wait
         will be.  But with debug ON, software ECC, and no DMA the wait is
         in many tens of minutes (and substantially  longer if many debug
         options are enabled.

         [I don't yet have data for the more optimal cases. It will be
          significantly less, but still not fast.]

      2. On subsequent boots, after the NXFFS file system has been created
         the delay will be less.  When the new file system is empty, it will
         be very fast.  But the NAND-related boot time can become substantial
         when there has been a lot of usage of the NAND.  This is because
         NXFFS needs to scan the NAND device and build the in-memory dataset
         needed to access NAND and there is more that must be scanned after
         the device has been used.  You may want to create a separate thread at
         boot time to bring up NXFFS so that you don't delay the boot-to-prompt
         time excessively in these longer delay cases.

      3. There is another NXFFS related performance issue:  When the FLASH
         is fully used, NXFFS will restructure the entire FLASH, the delay
         to restructure the entire FLASH will probably be even larger.  This
         solution in this case is to implement an NXFSS clean-up daemon that
         does the job a little-at-a-time so that there is no massive clean-up
         when the FLASH becomes full.

      4. Bad NXFFS behavior with NAND:  If you restart NuttX, the files that
         you wrote to NAND will be gone.  Why?  Because the multiple writes
         have corrupted the NAND ECC bits.  See STATUS below.  NXFFS would
         require a major overhaul to be usable with NAND.

    Using NAND with FAT
    -------------------

    If configured for FAT, the system will create block driver at
    /dev/mtdblock0:

      NuttShell (NSH)
      nsh> ls /dev
      /dev:
       console
       mtdblock0
       null
       ttyS0

    You will not that the system comes up immediately because there is not
    need to scan the volume in this case..

    The NSH 'mkfatfs' command can be used to format a FAT file system on
    NAND.

      nsh> mkfatfs /dev/mtdblock0

    This step, on the other hand, requires quite a bit of time.

    And the FAT file system can be mounted like:

      nsh> mount -t vfat /dev/mtdblock0 /mnt/nand
      nsh> ls /mnt/nand
      /mnt/nand:

      nsh> echo "This is a test" > /mnt/nand/atest.txt

        NOTE:  This will take a long time because it will require reading,
        modifying, and re-writing the 128KB erase page!

      nsh> ls -l /mnt/nand
      /mnt/nand:
       -rw-rw-rw-      16 atest.txt

      nsh> cat /mnt/fat/atest.txt
      This is a test

    NOTES:

    1. Unlike NXFFS, FAT can work with NAND (at least with PMECC disabled).
       But there are some significant issues.

    2. First, each NAND write access will cause a 256KB data transfer:  It
       will read the entire 128KB erase block, modify it and write it back
       to memory.  There is some caching logic so that this cached erase
       block can be re-used if possible and writes will be deferred as long
       as possible.

    3. If you hit a bad block, then FAT is finished.  There is no mechanism
       in place in FAT not to mark and skip over bad blocks.

    What is Needed
    --------------

    What is needed to work with FAT properly would be another MTD layer
    between the FTL layer and the NAND FLASH layer.  That layer would
    perform bad block detection and sparing so that FAT works transparently
    on top of the NAND.

    Another, less general, option would be support bad blocks within FAT.

  STATUS SUMMARY
  --------------

  1. PMECC appears to be working in that I can write a NAND block with its
     ECC and read the block back and verify that that is are no bit
     failures.  However, when attempting to work with FAT, it does not
     work correctly:  The MBR is written and read back correctly, but gets
     corrupted later for unknown reasons.

  2. DMA works (at least with software ECC), but I have seen occasional
     failures.  I recommend enabling DMA with caution.

     In NuttX, DMA will also cost two context switches (and, hence, four
     register state transfers).  With smaller NAND page sizes (say 2KiB and
     below), I would expect little or no performance improvement with DMA
     for this reason.

  3. NXFFS does not work with NAND. NAND differs from other other FLASH
     types several ways.  For one thing, NAND requires error correction
     (ECC) bytes that must be set in order to work around bit failures.
     This affects NXFFS in two ways:

     a. First, write failures are not fatal. Rather, they should be tried by
        bad blocks and simply ignored.  This is because unrecoverable bit
        failures will cause read failures when reading from NAND.  Setting
        the CONFIG_EXPERIMENTAL+CONFIG_NXFFS_NANDs option will enable this
        behavior.

     b. Secondly, NXFFS will write a block many times.  It tries to keep
        bits in the erased state and assumes that it can overwrite those bits
        to change them from the erased to the non-erased state.  This works
        will with NOR-like FLASH.  NAND behaves this way too.  But the
        problem with NAND is that the ECC bits cannot be re-written in this
        way.  So once a block has been written, it cannot be modified.  This
        behavior has NOT been fixed in NXFFS.  Currently, NXFFS will attempt
        to re-write the ECC bits causing the ECC to become corrupted because
        the ECC bits cannot be overwritten without erasing the entire block.

     This may prohibit NXFFS from ever being used with NAND.

  4. As mentioned above, FAT does work but (1) has some performance issues on
     writes and (2) cannot handle bad blocks.

AT24 Serial EEPROM
==================

  AT24 Connections
  ----------------

  A AT24C512 Serial EEPPROM was used for tested I2C.  There are other I2C/TWI
  devices on-board, but the serial EEPROM is the simplest test.

  There is, however, no AT24 EEPROM on board the SAMA5D3x-EK:  The Serial
  EEPROM was mounted on an external adaptor board and connected to the
  SAMA5D3x-EK thusly:

    - VCC -- VCC
    - GND -- GND
    - TWCK0(PA31) -- SCL
    - TWD0(PA30)  -- SDA

  By default, PA30 and PA31 are SWJ-DP pins, it can be used as a pin for TWI
  peripheral in the end application.

  Configuration Settings
  ----------------------

  The following configuration settings were used:

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_TWI0=y                   : Enable TWI0

    System Type -> TWI device driver options
      SAMA5_TWI0_FREQUENCY=100000           : Select a TWI frequency

    Device Drivers -> I2C Driver Support
      CONFIG_I2C=y                          : Enable I2C support
      CONFIG_I2C_TRANSFER=y                 : Driver supports the transfer() method
      CONFIG_I2C_WRITEREAD=y                : Driver supports the writeread() method

    Device Drivers -> Memory Technology Device (MTD) Support
      CONFIG_MTD=y                          : Enable MTD support
      CONFIG_MTD_AT24XX=y                   : Enable the AT24 driver
      CONFIG_AT24XX_SIZE=512                : Specifies the AT 24C512 part
      CONFIG_AT24XX_ADDR=0x53               : AT24 I2C address

    Application Configuration -> NSH Library
      CONFIG_NSH_ARCHINIT=y                 : NSH board-initialization

    File systems
      CONFIG_NXFFS=y                        : Enables the NXFFS file system
      CONFIG_NXFFS_PREALLOCATED=y           : Required
                                            : Other defaults are probably OK

    Board Selection
      CONFIG_SAMA5_AT24_AUTOMOUNT=y         : Mounts AT24 for NSH
      CONFIG_SAMA5_AT24_NXFFS=y             : Mount the AT24 using NXFFS

  You can then format the AT24 EEPROM for a FAT file system and mount the
  file system at /mnt/at24 using these NSH commands:

    nsh> mkfatfs /dev/mtdblock0
    nsh> mount -t vfat /dev/mtdblock0 /mnt/at24

  Then you an use the FLASH as a normal FAT file system:

    nsh> echo "This is a test" >/mnt/at24/atest.txt
    nsh> ls -l /mnt/at24
    /mnt/at24:
     -rw-rw-rw-      16 atest.txt
    nsh> cat /mnt/at24/atest.txt
    This is a test

I2C Tool
========

  I2C Tool. NuttX supports an I2C tool at apps/system/i2c that can be used
  to peek and poke I2C devices.  That tool cal be enabled by setting the
  following:

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_TWI0=y                   : Enable TWI0
      CONFIG_SAMA5_TWI1=y                   : Enable TWI1
      CONFIG_SAMA5_TWI2=y                   : Enable TWI2

    System Type -> TWI device driver options
      SAMA5_TWI0_FREQUENCY=100000           : Select a TWI0 frequency
      SAMA5_TWI1_FREQUENCY=100000           : Select a TWI1 frequency
      SAMA5_TWI2_FREQUENCY=100000           : Select a TWI2 frequency

    Device Drivers -> I2C Driver Support
      CONFIG_I2C=y                          : Enable I2C support
      CONFIG_I2C_TRANSFER=y                 : Driver supports the transfer() method
      CONFIG_I2C_WRITEREAD=y                : Driver supports the writeread() method

    Application Configuration -> NSH Library
      CONFIG_SYSTEM_I2CTOOL=y               : Enable the I2C tool
      CONFIG_I2CTOOL_MINBUS=0               : TWI0 has the minimum bus number 0
      CONFIG_I2CTOOL_MAXBUS=2               : TWI2 has the maximum bus number 2
      CONFIG_I2CTOOL_DEFFREQ=100000         : Pick a consistent frequency

    The I2C tool has extensive help that can be accessed as follows:

    nsh> i2c help
    Usage: i2c <cmd> [arguments]
    Where <cmd> is one of:

      Show help     : ?
      List busses   : bus
      List devices  : dev [OPTIONS] <first> <last>
      Read register : get [OPTIONS] [<repititions>]
      Show help     : help
      Write register: set [OPTIONS] <value> [<repititions>]
      Verify access : verf [OPTIONS] [<value>] [<repititions>]

    Where common "sticky" OPTIONS include:
      [-a addr] is the I2C device address (hex).  Default: 03 Current: 03
      [-b bus] is the I2C bus number (decimal).  Default: 0 Current: 0
      [-r regaddr] is the I2C device register address (hex).  Default: 00 Current: 00
      [-w width] is the data width (8 or 16 decimal).  Default: 8 Current: 8
      [-s|n], send/don't send start between command and data.  Default: -n Current: -n
      [-i|j], Auto increment|don't increment regaddr on repititions.  Default: NO Current: NO
      [-f freq] I2C frequency.  Default: 100000 Current: 100000

    NOTES:
    o Arguments are "sticky".  For example, once the I2C address is
      specified, that address will be re-used until it is changed.

    WARNING:
    o The I2C dev command may have bad side effects on your I2C devices.
      Use only at your own risk.

    As an example, the I2C dev comman can be used to list all devices
    responding on TWI0 (the default) like this:

      nsh> i2c dev 0x03 0x77
          0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
      00:          -- -- -- -- -- -- -- -- -- -- -- -- --
      10: -- -- -- -- -- -- -- -- -- -- 1a -- -- -- -- --
      20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
      30: -- -- -- -- -- -- -- -- -- 39 -- -- -- 3d -- --
      40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
      50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
      60: 60 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
      70: -- -- -- -- -- -- -- --
      nsh>

     Address 0x1a is the WM8904.  Address 0x39 is the SIL9022A. I am not sure
     what is at address 0x3d and 0x60

CAN Usage
=========
  I planned to verify CAN using the IXXAT USB-to-CAN Compact.  This section
  provides miscellaneous CAN-related notes, mostly to myself but perhaps of
  interest to others.

  [Unfortunately, as of this writing, I still do not have a proper CAN test
   bed to verify the CAN driver.]

  CAN Configuration
  -----------------

  The following steps illustrate how to enable CAN0 and/or CAN1 in the NuttX
  configuration:

    System Type -> SAMA5 Peripheral Support
       CONFIG_SAMA5_CAN0=y            : Select CAN0 and/or CAN1
       CONFIG_SAMA5_CAN1=y

    Device Drivers -> CAN Driver Support
       CONFIG_CAN=y                   : (Automatically selected)
       CONFIG_CAN_EXTID=y             : For extended, 29-bit CAN IDs

    System Type -> CAN Drive Support
       CONFIG_SAMA5_CAN0_BAUD=250000  : Select some BAUD for CAN0 (if enabled)
       CONFIG_SAMA5_CAN0_NRECVMB=1    : Select number of receive mailboxes (see below)
       CONFIG_SAMA5_CAN1_BAUD=250000  : Select some BAUD for CAN1 (if enabled)
       CONFIG_SAMA5_CAN1_NRECVMB=1    : Select number of receive mailboxes (see below)

  Receive Mailboxes and Address Filtering
  ---------------------------------------

  The SAMA5 CAN0 peripheral supports 8 mailboxes that can be used for sending
  and receiving messages.  Note that the number of dedicated receive mailboxes
  (CONFIG_SAMA5_CANn_NRECVMB) was set to one in the above configuration.  This
  could be set to any value from 1 to 3 (the upper limit of 3 is purely
  arbrary and can be increased with some minor code enhancement).  The
  remainder can be configured dynamically to send CAN messages.

  Why would you want to use more than one receive mailbox?  There are two
  reasons. Multiple receive mailboxes might needed to either (1) receive
  bursts of messages, or (2) to support multiple groups of messages filtered
  on message ID.

  You must also specify the address filtering for each dedicated receive mailbox:

    System Type -> CAN Drive Support
       CONFIG_SAMA5_CAN0_ADDR0 and CONFIG_SAMA5_CAN0_MASK0 : If CONFIG_SAMA5_CAN0_NRECVMB >= 1
       CONFIG_SAMA5_CAN0_ADDR1 and CONFIG_SAMA5_CAN0_MASK1 : If CONFIG_SAMA5_CAN0_NRECVMB >= 2
       CONFIG_SAMA5_CAN0_ADDR2 and CONFIG_SAMA5_CAN0_MASK2 : If CONFIG_SAMA5_CAN0_NRECVMB >= 3
       CONFIG_SAMA5_CAN1_ADDR0 and CONFIG_SAMA5_CAN1_MASK0 : If CONFIG_SAMA5_CAN1_NRECVMB >= 1
       CONFIG_SAMA5_CAN1_ADDR1 and CONFIG_SAMA5_CAN1_MASK1 : If CONFIG_SAMA5_CAN1_NRECVMB >= 2
       CONFIG_SAMA5_CAN1_ADDR2 and CONFIG_SAMA5_CAN1_MASK2 : If CONFIG_SAMA5_CAN1_NRECVMB >= 3

  Only messages that have IDs that match the CONFIG_SAMA5_CANn_ADDRn when both
  the received and the configured address are masked by CONFIG_SAMA5_CANn_MASKn
  will be accepted.  For example, if the mask is all ones, then only messasges
  with exact address matches will be accepted; if the mask is all zeroes than
  any address will be accepted.

  CAN connectors
  --------------

  CAN1 and CAN2 are available via RJ-11 connectors on the SAMA5Dx-EK.  Each
  is wired as follows.  Also shown below is the matching pins if you want connect
  the CAN to a device that uses an DB-9 connector (Such as the IXXAT USB-to-CAN
  Compact).  Both connector types (as well as RJ-45) are common.

                    +----------+     RJ-11       DB-9
                    |    O     |     ----------- --------------
  +------------+    |          |     Pin 1 3v3   Pin 1 N/C
  |    +--+    |    |  o5      |     Pin 2 5v    Pin 2 CANL
  |    |  |    |    |       o9 |     Pin 3 N/C   Pin 3 GND
  |  +-+  +-+  |    |  o4      |     Pin 4 CANL  Pin 4 N/C
  |  |      |  |    |       o8 |     Pin 5 CANH  Pin 5 N/C
  |  |654321|  |    |  o3      |     Pin 6 N/C   Pin 6 N/C
  |  |oooooo|  |    |       o7 |                 Pin 7 CANH
  |  +------+  |    |  o2      |                 Pin 8 N/C
  +------------+    |       o6 |                 Pin 9 CANV+ (N/C on IXXAT)   RJ-11 Female     |  x1      |
                    |          |
                    |    O     |
                    +----------+
                      DB-9 Male

SAMA5 ADC Support
=================

  Basic driver configuration
  --------------------------
  ADC support can be added to the NSH configuration.  However, there are no
  ADC input pins available to the user for ADC testing (the touchscreen ADC
  inputs are intended for other functionality).  Because of this, there is
  not much motivation to enable ADC support on the SAMA5D3x-EK.  This
  paragraph is included here, however, for people using a custom SAMA5D3x
  board that requires ADC support.

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_ADC=y               : Enable ADC driver support
      CONFIG_SAMA5_TC0=y               : Enable the Timer/counter library need for periodic sampling

    Drivers
      CONFIG_ANALOG=y                  : Should be automatically selected
      CONFIG_ADC=y                     : Should be automatically selected

    System Type -> ADC Configuration
      CONFIG_SAMA5_ADC_CHAN0=y         : These settings enable the sequencer to collect
      CONFIG_SAMA5_ADC_CHAN1=y         : Samples from ADC channels 0-3 on each trigger
      CONFIG_SAMA5_ADC_CHAN2=y
      CONFIG_SAMA5_ADC_CHAN3=y
      CONFIG_SAMA5_ADC_SEQUENCER=y

      CONFIG_SAMA5_ADC_TIOA0TRIG=y     : Trigger on the TC0, channel 0 output A
      CONFIG_SAMA5_ADC_TIOAFREQ=2      : At a frequency of 2Hz
      CONFIG_SAMA5_ADC_TIOA_RISING=y   : Trigger on the rising edge

    Default ADC settings (like gain and offset) may also be set if desired.

    System Type -> Timer/counter Configuration
      CONFIG_SAMA5_TC0_TIOA0=y         : Should be automatically selected

  Work queue supported is also needed:

    Library routines
      CONFIG_SCHED_WORKQUEUE=y

  ADC Test Example
  ----------------
  For testing purposes, there is an ADC program at apps/examples/adc that
  will collect a specified number of samples.  This test program can be
  enabled as follows:

    Application Configuration -> Examples -> ADC example
      CONFIG_EXAMPLES_ADC=y            : Enables the example code
      CONFIG_EXAMPLES_ADC_DEVPATH="/dev/adc0"

    Other default settings for the ADC example should be okay.

  ADC DMA Support
  ---------------
  At 2Hz, DMA is not necessary nor desire-able.  The ADC driver has support
  for DMA transfers of converted data (although that support has not been
  tested as of this writing).  DMA support can be added by include the
  following in the configuration.

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_DMAC1=y             : Enable DMAC1 support

    System Type -> ADC Configuration
      CONFIG_SAMA5_ADC_DMA=y           : Enable ADC DMA transfers
      CONFIG_SAMA5_ADC_DMASAMPLES=2    : Collect two sets of samples per DMA

    Drivers -> Analog device (ADC/DAC) support
      CONFIG_ADC_FIFOSIZE=16           : Driver may need a large ring buffer

    Application Configuration -> Examples -> ADC example
      CONFIG_EXAMPLES_ADC_GROUPSIZE=16 : Larger buffers in the test

SAMA5 PWM Support
=================

  Basic driver configuration
  --------------------------
  PWM support can be added to the NSH configuration.  However, there are no
  PWM output pins available to the user for PWM testing.  Because of this,
  there is not much motivation to enable PWM support on the SAMA5D3x-EK.  This
  paragraph is included here, however, for people using a custom SAMA5D3x
  board that requires PWM support.

  Basic driver configuration:

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_PWM=y               : Enable PWM driver support

    Drivers
      CONFIG_PWM=y                     : Should be automatically selected

    PWM Channel/Output Selection
    ----------------------------
    In order to use the PWM, you must enable one or more PWM Channels:

    System Type -> PWM Configuration
      CONFIG_SAMA5_PWM_CHAN0=y         : Enable one or more of channels 0-3
      CONFIG_SAMA5_PWM_CHAN1=y
      CONFIG_SAMA5_PWM_CHAN2=y
      CONFIG_SAMA5_PWM_CHAN3=y

    For each channel that is enabled, you must also specify the output pins
    to be enabled and the clocking supplied to the PWM channel.

      CONFIG_SAMA5_PWM_CHANx_FAULTINPUT=n : (not used currently)
      CONFIG_SAMA5_PWM_CHANx_OUTPUTH=y  : Enable One of both of the H and L output pins
      CONFIG_SAMA5_PWM_CHANx_OUTPUTL=y

    Where x=0..3.

    Care must be taken because all PWM output pins conflict with some other
    usage of the pin by other devices.  Furthermore, many of these pins have
    not been brought out to an external connector:

      -----+---+---+----+------+----------------
       PWM  PIN PER PIO   I/O   CONFLICTS
      -----+---+---+----+------+----------------
       PWM0 FI   B  PC28 J2.30  SPI1, ISI
            H    B  PB0   ---   GMAC
                 B  PA20 J1.14  LCDC, ISI
            L    B  PB1   ---   GMAC
                 B  PA21 J1.16  LCDC, ISI
      -----+---+---+----+------+----------------
       PWM1 FI   B  PC31 J2.36  HDMI
            H    B  PB4   ---   GMAC
                 B  PA22 J1.18  LCDC, ISI
            L    B  PB5   ---   GMAC
                 B  PE31 J3.20  ISI, HDMI
                 B  PA23 J1.20  LCDC, ISI
      -----+---+---+----+------+----------------
       PWM2 FI   B  PC29 J2.29  UART0, ISI, HDMI
            H    C  PD5   ---   HSMCI0
                 B  PB8   ---   GMAC
            L    C  PD6   ---   HSMCI0
                 B  PB9   ---   GMAC
      -----+---+---+----+------+----------------
       PWM3 FI   C  PD16  ---  SPI0, Audio
            H    C  PD7   ---  HSMCI0
                 B  PB12 J3.7  GMAC
            L    C  PD8   ---  HSMCI0
                 B  PB13  ---  GMAC
      -----+---+---+----+--------------------

    See configs/sama5d3x-ek/include/board.h for all of the default PWM
    pin selections.  I used PWM channel 0, pins PA20 and PA21 for testing.

    Clocking is addressed in the next paragraph.

    PWM Clock Configuration
    -----------------------
    PWM Channels can be clocked from either a coarsely divided divided down
    MCK or from a custom frequency from PWM CLKA and/or CLKB.  If you want
    to use CLKA or CLKB, you must enable and configure them.

    System Type -> PWM Configuration
      CONFIG_SAMA5_PWM_CLKA=y
      CONFIG_SAMA5_PWM_CLKA_FREQUENCY=3300
      CONFIG_SAMA5_PWM_CLKB=y
      CONFIG_SAMA5_PWM_CLKB_FREQUENCY=3300

    Then for each of the enabled, channels you must select the input clock
    for that channel:

    System Type -> PWM Configuration
      CONFIG_SAMA5_PWM_CHANx_CLKA=y     : Pick one of MCK, CLKA, or CLKB (only)
      CONFIG_SAMA5_PWM_CHANx_CLKB=y
      CONFIG_SAMA5_PWM_CHANx_MCK=y
      CONFIG_SAMA5_PWM_CHANx_MCKDIV=128 : If MCK is selected, then the MCK divider must
                                        : also be provided (1,2,4,8,16,32,64,128,256,512, or 1024).

  PWM Test Example
  ----------------
  For testing purposes, there is an PWM program at apps/examples/pwm that
  will collect a specified number of samples.  This test program can be
  enabled as follows:

    Application Configuration -> Examples -> PWM example
      CONFIG_EXAMPLES_PWM=y            : Enables the example code

    Other default settings for the PWM example should be okay.

      CONFIG_EXAMPLES_PWM_DEVPATH="/dev/pwm0"
      CONFIG_EXAMPLES_PWM_FREQUENCY=100

  Usage of the example is straightforward:

    nsh> pwm -h
    Usage: pwm [OPTIONS]

    Arguments are "sticky".  For example, once the PWM frequency is
    specified, that frequency will be re-used until it is changed.

    "sticky" OPTIONS include:
      [-p devpath] selects the PWM device.  Default: /dev/pwm0 Current: /dev/pwm0
      [-f frequency] selects the pulse frequency.  Default: 100 Hz Current: 100 Hz
      [-d duty] selects the pulse duty as a percentage.  Default: 50 % Current: 50 %
      [-t duration] is the duration of the pulse train in seconds.  Default: 5 Current: 5
      [-h] shows this message and exits

RTC
===

  The Real Time Clock/Calendar RTC) may be enabled with these settings:

    System Type:
      CONFIG_SAMA5_RTC=y                   : Enable the RTC driver

    Drivers (these values will be selected automatically):
      CONFIG_RTC=y                         : Use the RTC for system time
      CONFIG_RTC_DATETIME=y                : RTC supports data/time

  The RTC supports an alarm that may be enable with the following settings.
  However, there is nothing in the system that currently makes use of this
  alarm.

    Drivers:
      CONFIG_RTC_ALARM=y                   : Enable the RTC alarm

    Library Routines
      CONFIG_SCHED_WORKQUEUE=y              : Alarm needs work queue support

Watchdog Timer
==============

  NSH can be configured to exercise the watchdog timer test
  (apps/examples/watchdog).  This can be selected with the following
  settings in the NuttX configuration file:

    System Type:
      CONFIG_SAMA5_WDT=y                  : Enable the WDT peripheral
                                          : Defaults in "RTC Configuration" should be OK

    Drivers (this will automatically be selected):
      CONFIG_WATCHDOG=y                   : Enables watchdog timer driver support

    Application Configuration -> Examples
      CONFIG_EXAMPLES_WATCHDOG=y          : Enable apps/examples/watchdog

  The WDT timer is driven off the slow, 32768Hz clock divided by 128. As a
  result, the watchdog a maximum timeout value of 16 seconds.  The SAMA5 WDT
  may also only be programmed one time; the processor must be reset before
  the WDT can be reprogrammed.

  The SAMA5 always boots with the watchdog timer enabled at its maximum
  timeout (16 seconds).  In the normal case where no watchdog timer driver
  has been configured, the watchdog timer is disabled as part of the start
  up logic.  But, since we are permitted only one opportunity to program
  the WDT, we cannot disable the watchdog time if CONFIG_SAMA5_WDT=y.  So,
  be forewarned:  You have only 16 seconds to run your watchdog timer test!

  NOTE:  If you are using the norboot program to run from FLASH as I did,
  beware that the default version also disables the watchdog.  You will
  need a special version of norboot with CONFIG_SAMA5_WDT=y.

TRNG and /dev/random
====================

  NSH can be configured to enable the SAMA5 TRNG peripheral so that it
  provides /dev/random.  The following configuration will enable the TRNG,
  /dev/random, and the simple test of /dev/random at apps/examples/ranadom:

    System Type:
      CONFIG_SAMA5_TRNG=y                 : Enable the TRNG peripheral

    Drivers (automatically selected):
      CONFIG_DEV_RANDOM=y                 : Enable /dev/random

    Applications -> Examples
      CONFIG_EXAMPLES_RANDOM=y            : Enable apps/examples/random
      CONFIG_EXAMPLES_MAXSAMPLES=64       : Default settings are probably OK
      CONFIG_EXAMPLES_NSAMPLES=8

Touchscreen Testing
===================

  You can enable the touchscreen by modifying the configuration in the
  following ways:

    System Type:
      CONFIG_SAMA5_ADC=y                  : ADC support is required
      CONFIG_SAMA5_TSD=y                  : Enabled touchcreen device support
      SAMA5_TSD_4WIRE=y                   : 4-Wire interface with pressure

  You might want to tinker with the SWAPXY and THRESHX and THRESHY settings
  to get the result that you want.

    Drivers:
      CONFIG_INPUT=y                      : (automatically selected)

    Board Selection:
       CONFIG_SAMA5_TSD_DEVMINOR=0        : Register as /dev/input0

    Library Support:
      CONFIG_SCHED_WORKQUEUE=y            : Work queue support required

  These options may also be applied to enable a built-in touchscreen test
  application:

    Application Configuration:
      CONFIG_EXAMPLES_TOUCHSCREEN=y       : Enable the touchscreen built-int test
      CONFIG_EXAMPLES_TOUCHSCREEN_MINOR=0 : To match the board selection
      CONFIG_EXAMPLES_TOUCHSCREEN_DEVPATH="/dev/input0"

  Defaults should be okay for all related settings.

OV2640 Camera Interface
=======================

    SAMA5D3x PIN             SAMA5D3x-EK    OV2640
    PIO  PER SIGNAL        ISI Socket J11
    ---- --- ------------- --- ------------ ----------------------------------------
    ---                     1  VDDISI       ---
    ---                     2  GND          ---
    ---                     3  VDDISI       ---
    ---                     4  GND          ---
    PE28  ?  ?              5  ZB_SLPTR     ???
    PE29  ?  ?              6  ZB_RST       C6 RESETB Reset mode (?)
    PC27  B  TWI1_CK        7  TWCK1        C2 SIO_C SCCB serial interface clock input
    PC26  B  TWI1_D         8  TWD1         C1 SIO_D SCCB serial interface data I/O
    ---                     9  GND          ---
    PD31  B  PCK1 (ISI_MCK) 10 ISI_MCK      C4 XVCLK System clock input (?)
    ---                     11 GND          ---
    PA30  C  ISI_VSYNC      12 ISI_VSYNC    D2 VSYNC Vertical synchronization
    ---                     13 GND          ---
    PA31  C  ISI_HSYNC      14 ISI_HSYNC    C3 HREF Horizontal reference output (?)
    ---                     15 GND          ---
    PC30  C  ISI_PCK        16 ISI_PCK      E3 PCLK Pixel clock output
    ---                     17 GND          ---
    PA16  C  ISI_D0         18 ISI_D0       E2 Y0 Video port output bit[0]
    PA17  C  ISI_D1         19 ISI_D1       E1 Y1 Video port output bit[1]
    PA18  C  ISI_D2         20 ISI_D2       F3 Y2 Video port output bit[2]
    PA19  C  ISI_D3         21 ISI_D3       G3 Y3 Video port output bit[3]
    PA20  C  ISI_D4         22 ISI_D4       F4 Y4 Video port output bit[4]
    PA21  C  ISI_D5         23 ISI_D5       G4 Y5 Video port output bit[5]
    PA22  C  ISI_D6         24 ISI_D6       E5 Y6 Video port output bit[6]
    PA23  C  ISI_D7         25 ISI_D7       G5 Y7 Video port output bit[7]
    PC29  C  ISI_D8         26 ISI_D8       F5 Y8 Video port output bit[8]
    PC28  C  ISI_D9         27 ISI_D9       G6 Y9 Video port output bit[9]
    PC27  C  ISI_D10        28 ISI_D10      ---
    PC26  C  ISI_D11        29 ISI_D11      ---
    ---                     30 GND          ---

    ???                     ??              A2 EXPST_B Snapshot exposure start trigger
    ???                     ??              A6 STROBE  Flash control output
    ???                     ??              B2 FREX    Snapshot trigger
    ???                     ??              B6 PWDN    Power-down mode enable

I2S Audio Support
=================

  The SAMA5D3x-EK has two devices on-board that can be used for verification
  of I2S functionality:  HDMI and a WM8904 audio CODEC.  As of this writing,
  the I2S driver is present, but there are not drivers for either the HDMI
  or the WM8904.

  WM8904 Audio CODEC Interface
  ----------------------------

    ------------- ---------------- -----------------
    WM8904        SAMA5D3          NuttX Pin Name
    ------------- ---------------- -----------------
     3 SDA        PA30 TWD0        PIO_TWI0_D
     2 SCLK       PA31 TWCK0       PIO_TWI0_CK
    28 MCLK       PD30 PCK0        PIO_PMC_PCK0
    29 BCLK/GPIO4 PC16 TK          PIO_SSC0_TK
    "" "        " PC19 RK          PIO_SSC0_RK
    30 LRCLK      PC17 TF          PIO_SSC0_TF
    "" "   "      PC20 RF          PIO_SSC0_RF
    31 ADCDAT     PC21 RD          PIO_SSC0_RD
    32 DACDAT     PC18 TD          PIO_SSC0_TD
     1 IRQ/GPIO1  PD16 INT_AUDIO   N/A
    ------------- ---------------- -----------------

  I2S Loopback Test
  -----------------

  The I2S driver was verified using a special I2C character driver (at
  nuttx/drivers/audio/i2schar.c) and a test driver at apps/examples/i2schar.
  The I2S driver was verified in loopback mode with no audio device.

  [NOTE: The above statement is anticipatory:  As of this writing I2S driver
   verification is underway and still not complete].

  This section describes the modifications to the NSH configuration that were
  used to perform the I2S testing:

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_SSCO=y              : Enable SSC0 driver support
      CONFIG_SAMA5_DMAC0=y             : DMAC0 required by SSC0

    Alternatively, SSC1 could have be used:

    System Type -> SAMA5 Peripheral Support
      CONFIG_SAMA5_SSC1=y              : Enable SSC0 driver support
      CONFIG_SAMA5_DMAC1=y             : DMAC0 required by SSC0

    System Type -> SSC Configuration
      CONFIG_SAMA5_SSC_MAXINFLIGHT=16  : Up to 16 pending DMA transfers
      CONFIG_SAMA5_SSC0_MASTER=y       : Master mode
      CONFIG_SAMA5_SSC0_DATALEN=16     : 16-bit data
      CONFIG_SAMA5_SSC0_RX=y           : Support a receiver
      CONFIG_SAMA5_SSC0_RX_RKINPUT=y   : Receiver gets clock from RK input
      CONFIG_SAMA5_SSC0_TX=y           : Support a transmitter
      CONFIG_SAMA5_SSC0_TX_MCKDIV=y    : Transmitter gets clock from MCK/2
      CONFIG_SAMA5_SSC0_MCKDIV_SAMPLERATE=48000 : Sampling at 48K samples/sec
      CONFIG_SAMA5_SSC0_TX_TKOUTPUT_XFR=y  : Outputs clock on TK when transferring data
      CONFIG_SAMA5_SSC0_LOOPBACK=y     : Loopmode mode connects RD/TD and RK/TK

    Audio
      CONFIG_AUDIO=y                   : Audio support needed
                                       : Defaults should be okay

    Drivers -> Audio
      CONFIG_I2S=y                     : General I2S support
      CONFIG_AUDIO_DEVICES=y           : Audio device support
      CONFIG_AUDIO_I2SCHAR=y           : Build I2S character driver

    The following describes how I have the test application at
    apps/examples/i2schar configured:

      CONFIG_EXAMPLES_I2SCHAR=y
      CONFIG_EXAMPLES_I2SCHAR_DEVPATH="/dev/i2schar0"
      CONFIG_EXAMPLES_I2SCHAR_TX=y
      CONFIG_EXAMPLES_I2SCHAR_TXBUFFERS=4
      CONFIG_EXAMPLES_I2SCHAR_TXSTACKSIZE=1536
      CONFIG_EXAMPLES_I2SCHAR_RX=y
      CONFIG_EXAMPLES_I2SCHAR_RXBUFFERS=4
      CONFIG_EXAMPLES_I2SCHAR_RXSTACKSIZE=1536
      CONFIG_EXAMPLES_I2SCHAR_BUFSIZE=256
      CONFIG_EXAMPLES_I2SCHAR_DEVINIT=y

    Board Selection
      CONFIG_SAMA5D3X_EK_I2SCHAR_MINOR=0
      CONFIG_SAMA5D3X_EK_SSC_PORT=0     : 0 or SSC0, 1 for SSC1

    Library Routines
      CONFIG_SCHED_WORKQUEUE=y          : Driver needs work queue support

SAMA5D3x-EK Configuration Options
=================================

  CONFIG_ARCH - Identifies the arch/ subdirectory.  This should
  be set to:

    CONFIG_ARCH="arm"

  CONFIG_ARCH_family - For use in C code:

    CONFIG_ARCH_ARM=y

  CONFIG_ARCH_architecture - For use in C code:

    CONFIG_ARCH_CORTEXA5=y

  CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory

    CONFIG_ARCH_CHIP="sama5"

  CONFIG_ARCH_CHIP_name - For use in C code to identify the exact
  chip:

    CONFIG_ARCH_CHIP_SAMA5=y

  and one of:

   CONFIG_ARCH_CHIP_ATSAMA5D31=y
   CONFIG_ARCH_CHIP_ATSAMA5D33=y
   CONFIG_ARCH_CHIP_ATSAMA5D34=y
   CONFIG_ARCH_CHIP_ATSAMA5D35=y

  CONFIG_ARCH_BOARD - Identifies the configs subdirectory and
  hence, the board that supports the particular chip or SoC.

    CONFIG_ARCH_BOARD="sama5d3x-ek" (for the SAMA5D3x-EK development board)

  CONFIG_ARCH_BOARD_name - For use in C code

    CONFIG_ARCH_BOARD_SAMA5D3X_EK=y

  CONFIG_ARCH_LOOPSPERMSEC - Must be calibrated for correct operation
  of delay loops

  CONFIG_ENDIAN_BIG - define if big endian (default is little
  endian)

  CONFIG_RAM_SIZE - Describes the installed DRAM (SRAM in this case):

    CONFIG_RAM_SIZE=0x0002000 (128Kb)

  CONFIG_RAM_START - The physical start address of installed DRAM

    CONFIG_RAM_START=0x20000000

  CONFIG_RAM_VSTART - The virutal start address of installed DRAM

    CONFIG_RAM_VSTART=0x20000000

  CONFIG_ARCH_IRQPRIO - The SAM3UF103Z supports interrupt prioritization

    CONFIG_ARCH_IRQPRIO=y

  CONFIG_ARCH_LEDS - Use LEDs to show state. Unique to boards that
  have LEDs

  CONFIG_ARCH_INTERRUPTSTACK - This architecture supports an interrupt
  stack. If defined, this symbol is the size of the interrupt
  stack in bytes.  If not defined, the user task stacks will be
  used during interrupt handling.

  CONFIG_ARCH_STACKDUMP - Do stack dumps after assertions

  CONFIG_ARCH_LEDS -  Use LEDs to show state. Unique to board architecture.

  CONFIG_ARCH_CALIBRATION - Enables some build in instrumentation that
  cause a 100 second delay during boot-up.  This 100 second delay
  serves no purpose other than it allows you to calibrate
  CONFIG_ARCH_LOOPSPERMSEC.  You simply use a stop watch to measure
  the 100 second delay then adjust CONFIG_ARCH_LOOPSPERMSEC until
  the delay actually is 100 seconds.

  Individual subsystems can be enabled:

    CONFIG_SAMA5_DBGU        - Debug Unit Interrupt
    CONFIG_SAMA5_PIT         - Periodic Interval Timer Interrupt
    CONFIG_SAMA5_WDT         - Watchdog timer Interrupt
    CONFIG_SAMA5_HSMC        - Multi-bit ECC Interrupt
    CONFIG_SAMA5_SMD         - SMD Soft Modem
    CONFIG_SAMA5_USART0      - USART 0
    CONFIG_SAMA5_USART1      - USART 1
    CONFIG_SAMA5_USART2      - USART 2
    CONFIG_SAMA5_USART3      - USART 3
    CONFIG_SAMA5_UART0       - UART 0
    CONFIG_SAMA5_UART1       - UART 1
    CONFIG_SAMA5_TWI0        - Two-Wire Interface 0
    CONFIG_SAMA5_TWI1        - Two-Wire Interface 1
    CONFIG_SAMA5_TWI2        - Two-Wire Interface 2
    CONFIG_SAMA5_HSMCI0      - High Speed Multimedia Card Interface 0
    CONFIG_SAMA5_HSMCI1      - High Speed Multimedia Card Interface 1
    CONFIG_SAMA5_HSMCI2      - High Speed Multimedia Card Interface 2
    CONFIG_SAMA5_SPI0        - Serial Peripheral Interface 0
    CONFIG_SAMA5_SPI1        - Serial Peripheral Interface 1
    CONFIG_SAMA5_TC0         - Timer Counter 0 (ch. 0, 1, 2)
    CONFIG_SAMA5_TC1         - Timer Counter 1 (ch. 3, 4, 5)
    CONFIG_SAMA5_PWM         - Pulse Width Modulation Controller
    CONFIG_SAMA5_ADC         - Touch Screen ADC Controller
    CONFIG_SAMA5_DMAC0       - DMA Controller 0
    CONFIG_SAMA5_DMAC1       - DMA Controller 1
    CONFIG_SAMA5_UHPHS       - USB Host High Speed
    CONFIG_SAMA5_UDPHS       - USB Device High Speed
    CONFIG_SAMA5_GMAC        - Gigabit Ethernet MAC
    CONFIG_SAMA5_EMAC        - Ethernet MAC
    CONFIG_SAMA5_LCDC        - LCD Controller
    CONFIG_SAMA5_ISI         - Image Sensor Interface
    CONFIG_SAMA5_SSC0        - Synchronous Serial Controller 0
    CONFIG_SAMA5_SSC1        - Synchronous Serial Controller 1
    CONFIG_SAMA5_CAN0        - CAN controller 0
    CONFIG_SAMA5_CAN1        - CAN controller 1
    CONFIG_SAMA5_SHA         - Secure Hash Algorithm
    CONFIG_SAMA5_AES         - Advanced Encryption Standard
    CONFIG_SAMA5_TDES        - Triple Data Encryption Standard
    CONFIG_SAMA5_TRNG        - True Random Number Generator
    CONFIG_SAMA5_ARM         - Performance Monitor Unit
    CONFIG_SAMA5_FUSE        - Fuse Controller
    CONFIG_SAMA5_MPDDRC      - MPDDR controller

  Some subsystems can be configured to operate in different ways. The drivers
  need to know how to configure the subsystem.

    CONFIG_SAMA5_PIOA_IRQ    - Support PIOA interrupts
    CONFIG_SAMA5_PIOB_IRQ    - Support PIOB interrupts
    CONFIG_SAMA5_PIOC_IRQ    - Support PIOD interrupts
    CONFIG_SAMA5_PIOD_IRQ    - Support PIOD interrupts
    CONFIG_SAMA5_PIOE_IRQ    - Support PIOE interrupts

    CONFIG_USART0_ISUART     - USART0 is configured as a UART
    CONFIG_USART1_ISUART     - USART1 is configured as a UART
    CONFIG_USART2_ISUART     - USART2 is configured as a UART
    CONFIG_USART3_ISUART     - USART3 is configured as a UART

  ST91SAMA5 specific device driver settings

    CONFIG_U[S]ARTn_SERIAL_CONSOLE - selects the USARTn (n=0,1,2,3) or UART
           m (m=4,5) for the console and ttys0 (default is the USART1).
    CONFIG_U[S]ARTn_RXBUFSIZE - Characters are buffered as received.
       This specific the size of the receive buffer
    CONFIG_U[S]ARTn_TXBUFSIZE - Characters are buffered before
       being sent.  This specific the size of the transmit buffer
    CONFIG_U[S]ARTn_BAUD - The configure BAUD of the UART.  Must be
    CONFIG_U[S]ARTn_BITS - The number of bits.  Must be either 7 or 8.
    CONFIG_U[S]ARTn_PARTIY - 0=no parity, 1=odd parity, 2=even parity
    CONFIG_U[S]ARTn_2STOP - Two stop bits

  AT91SAMA5 USB Host Configuration
  Pre-requisites

    CONFIG_USBDEV          - Enable USB device support
    CONFIG_USBHOST         - Enable USB host support
    CONFIG_SAMA5_UHPHS     - Needed
    CONFIG_SAMA5_OHCI      - Enable the STM32 USB OTG FS block
    CONFIG_SCHED_WORKQUEUE - Worker thread support is required

  Options:

    CONFIG_SAMA5_OHCI_NEDS
      Number of endpoint descriptors
    CONFIG_SAMA5_OHCI_NTDS
      Number of transfer descriptors
    CONFIG_SAMA5_OHCI_TDBUFFERS
      Number of transfer descriptor buffers
    CONFIG_SAMA5_OHCI_TDBUFSIZE
      Size of one transfer descriptor buffer
    CONFIG_USBHOST_INT_DISABLE
      Disable interrupt endpoint support
    CONFIG_USBHOST_ISOC_DISABLE
      Disable isochronous endpoint support
    CONFIG_USBHOST_BULK_DISABLE
      Disable bulk endpoint support

config SAMA5_OHCI_REGDEBUG

Configurations
==============

  Information Common to All Configurations
  ----------------------------------------
  Each SAM3U-EK configuration is maintained in a sub-directory and
  can be selected as follow:

    cd tools
    ./configure.sh sama5d3x-ek/<subdir>
    cd -
    . ./setenv.sh

  Before sourcing the setenv.sh file above, you should examine it and perform
  edits as necessary so that TOOLCHAIN_BIN is the correct path to the directory
  than holds your toolchain binaries.

  And then build NuttX by simply typing the following.  At the conclusion of
  the make, the nuttx binary will reside in an ELF file called, simply, nuttx.

    make

  The <subdir> that is provided above as an argument to the tools/configure.sh
  must be is one of the following.

  NOTES:

  1. These configurations use the mconf-based configuration tool.  To
    change any of these configurations using that tool, you should:

    a. Build and install the kconfig-mconf tool.  See nuttx/README.txt
       and misc/tools/

    b. Execute 'make menuconfig' in nuttx/ in order to start the
       reconfiguration process.

  2. Unless stated otherwise, all configurations generate console
     output on UART0 (J3).

  3. All of these configurations use the Code Sourcery for Windows toolchain
     (unless stated otherwise in the description of the configuration).  That
     toolchain selection can easily be reconfigured using 'make menuconfig'.
     Here are the relevant current settings:

     Build Setup:
       CONFIG_HOST_WINDOWS=y               : Microsoft Windows
       CONFIG_WINDOWS_CYGWIN=y             : Using Cygwin or other POSIX environment

     System Type -> Toolchain:
       CONFIG_ARMV7A_TOOLCHAIN_GNU_EABIW=y : GNU EABI toolchain for windows

     That same configuration will work with Atmel GCC toolchain.  The only
     change required to use the Atmel GCC toolchain is to change the PATH
     variable so that those tools are selected instead of the CodeSourcery
     tools.  Try 'which arm-none-eabi-gcc' to make sure that you are
     selecting the right tool.

     The setenv.sh file is available for you to use to set the PATH
     variable.  The path in the that file may not, however, be correct
     for your installation.

     See also the "NOTE about Windows native toolchains" in the section call
     "GNU Toolchain Options" above.

     !!!WARNING!!! The first time that you type 'make', the system will
     configure itself based on the settings in the .config file.  One of
     these settings can cause a lot of confusion if you configure the build
     in the wrong state:  If you are running on Linux, make *certain* that
     you have CONFIG_HOST_LINUX=y *before* the first make or you will
     create a very corrupt configuration that may not be easy to recover
     from.

  Configuration Sub-directories
  -----------------------------
  Summary:  Some of the descriptions below are long and wordy. Here is the
  concise summary of the available SAMA5D3x-EK configurations:

    demo: This is an NSH configuration that supports as much functionality
      as possible.  That is why it gets its name:  It attempts to show as
      much as possible
    hello:  The tiniest configuration possible (almost).  It just says
      "Hello, World!"  On the serial console.  It is so tiny that it is
      able to run entirely out of internal SRAM (all of the other
      configurations except norboot use NOR FLASH for .text and internal
      SRAM for .data and .bass).  This configuration is only useful for
      bring-up.
    norboot:
      This is a little program to help debug of code in NOR flash.  I wrote
      it because I don't yet understand how to get the SAMA5 to boot from
      NOR FLASH.  See the description below and the section above entitled
      "Creating and Using NORBOOT" for more information
    nsh:  This is another NSH configuration, not too different from the
      demo configuration.  The nsh configuration is, however, bare bones.
      It is the simplest possible NSH configuration and is useful as a
      platform for debugging and integrating new features in isolation.
    nx: A simple test using the NuttX graphics system (NX) that has been
      used to verify the SAMA5D3x-EK TFT LCD.  This test case focuses on
      general window controls, movement, mouse and keyboard input.  It
      requires no user interaction.
   nxwm: This is a special configuration setup for the NxWM window manager
      UnitTest.  It integrates support for both the SAMA5 LCDC and the
      SAMA5 ADC touchscreen controller and provides a more advance
      graphics demo. It provides an interactive windowing experience.
   ov2640:  A test of the SAMA5 ISI using an OV2640 camera.

  There may be issues with some of these configurations.  See the details
  before of the status of individual configurations.

  Now for the gory details:

  demo:

    This configuration directory provide the NuttShell (NSH).  There are
    two NSH configurations:  nsh and demo.  The difference is that nsh is
    intended to be a very simple NSH configuration upon which you can build
    further functionality.  The demo configuration, on the other hand, is
    intended to be a rich configuration that shows many features all working
    together.

    See also the NOTES associated with the nsh configuration for other hints
    about features that can be included with this configuration.

    NOTES:
    1. This configuration uses the default USART1 serial console.  That
       is easily changed by reconfiguring to (1) enable a different
       serial peripheral, and (2) selecting that serial peripheral as
       the console device.

    2. By default, this configuration is set up to build on Windows
       under either a Cygwin or MSYS environment using a recent, Windows-
       native, generic ARM EABI GCC toolchain (such as the CodeSourcery
       toolchain).  Both the build environment and the toolchain
       selection can easily be changed by reconfiguring:

       CONFIG_HOST_WINDOWS=y                   : Windows operating system
       CONFIG_WINDOWS_CYGWIN=y                 : POSIX environment under windows
       CONFIG_ARMV7A_TOOLCHAIN_CODESOURCERYW=y : CodeSourcery for Windows

       If you are running on Linux, make *certain* that you have
       CONFIG_HOST_LINUX=y *before* the first make or you will create a
       corrupt configuration that may not be easy to recover from. See
       the warning in the section "Information Common to All Configurations"
       for further information.

    3. This configuration executes out of CS0 NOR flash and can only
       be loaded via SAM-BA.  The are the relevant configuration options
       are provided above in the section entitled "NOR FLASH Support".

    4. Data resides in ISRAM, but can be moved to SDRAM as described above
       under "SDRAM Data Configuration."

    The following features are pre-enabled in the demo configuration, but not
    in the nsh configuration:

    5. SDRAM is supported.  .data and .bss is still retained in ISRAM, but
       SDRAM is initializeed and the SDRAM memory is included in the heap.
       Relevant configuration settings are provided in the paragraph entitled
       "SDRAM Support" above.

    6. The Real Time Clock/Calendar RTC) is enabled.  See the section entitled
       "RTC" above.

    7. The Embest or Ronetix CPU module includes an Atmel AT25DF321A,
       32-megabit, 2.7-volt SPI serial flash.  Support for that serial
       FLASH can is enabled in this configuration.  See the paragraph
       entitle "AT25 Serial FLASH" for detailed configuration settings.

    8. Support for HSMCI car slots. The SAMA5D3x-EK provides a two SD memory
       card slots:  (1) a full size SD card slot (J7 labelled MCI0), and (2)
       a microSD memory card slot (J6 labelled MCI1).  The full size SD card
       slot connects via HSMCI0; the microSD connects vi HSMCI1.  Relevant
       configuration settings can be found in the section entitle "HSMCI
       Card Slots" above.

    9. Support the USB high-speed device (UDPHS) driver is enabled.  See the
       section above entitled "USB High-Speed Device" for relevant NuttX
       configuration settings.

    10. The USB high-speed EHCI and the low-/full- OHCI host drivers are supported
        in this configuration.  See the section above entitle "USB High-Speed Host"
        for relevant configuration information.

    11. Support SAMA5D3 TRNG peripheral is enabled so that it provides
        /dev/random.  See the section entitled "TRNG and /dev/random"
        above for detailed configuration information.

    STATUS:
       See the To-Do list below

  hello:

    This configuration directory, performs the (almost) simplest of all
    possible examples:  examples/hello.  This just comes up, says hello
    on the serial console and terminates.  This configuration is of
    value during bring-up because it is small and can run entirely out
    of internal SRAM.

    NOTES:
    1. This configuration uses the default USART1 serial console.  That
       is easily changed by reconfiguring to (1) enable a different
       serial peripheral, and (2) selecting that serial peripheral as
       the console device.

    2. By default, this configuration is set up to build on Windows
       under either a Cygwin or MSYS environment using a recent, Windows-
       native, generic ARM EABI GCC toolchain (such as the CodeSourcery
       toolchain).  Both the build environment and the toolchain
       selection can easily be changed by reconfiguring:

       CONFIG_HOST_WINDOWS=y                   : Windows operating system
       CONFIG_WINDOWS_CYGWIN=y                 : POSIX environment under windows
       CONFIG_ARMV7A_TOOLCHAIN_CODESOURCERYW=y : CodeSourcery for Windows

       If you are running on Linux, make *certain* that you have
       CONFIG_HOST_LINUX=y *before* the first make or you will create a
       corrupt configuration that may not be easy to recover from. See
       the warning in the section "Information Common to All Configurations"
       for further information.

    3. This configuration executes out of internal SRAM and can only
       be loaded via JTAG.

       CONFIG_SAMA5_BOOT_ISRAM=y               : Boot into internal SRAM
       CONFIG_BOOT_RUNFROMISRAM=y              : Run from internal SRAM

    STATUS:
       See the To-Do list below

  norboot:
    This is a little program to help debug of code in NOR flash.  It
    does the following:

    - It enables and configures NOR FLASH, then
    - Waits for you to break in with GDB.

    At that point, you can set the PC and begin executing from NOR FLASH
    under debug control.  See the section entitled "Creating and Using
    NORBOOT" above.

    NOTES:

    1. This program derives from the hello configuration.  All of the
       notes there apply to this configuration as well.

    2. The default norboot program initializes the NOR memory,
       displays a message and halts.  The norboot program can also be
       configured to jump directly into NOR FLASH without requiring the
       final halt and go by setting CONFIG_SAMA5_NOR_START=y in the
       NuttX configuration.

    3. Be aware that the default norboot also disables the watchdog.
       Since you will not be able to re-enable the watchdog later, you may
       need to set CONFIG_SAMA5_WDT=y in the NuttX configuration file.

    4. If you put norboot on the Serial FLASH, you can automatically
       boot to NOR on reset.  See the section "Creating and Using NORBOOT"
       above.

    STATUS:
       See the To-Do list below

  nsh:

    This configuration directory provide the NuttShell (NSH).  There are
    two NSH configurations:  nsh and demo.  The difference is that nsh is
    intended to be a very simple NSH configuration upon which you can build
    further functionality.  The demo configuration, on the other hand, is
    intended to be a rich configuration that shows many features all working
    together.

    NOTES:
    1. This configuration uses the default USART1 serial console.  That
       is easily changed by reconfiguring to (1) enable a different
       serial peripheral, and (2) selecting that serial peripheral as
       the console device.

    2. By default, this configuration is set up to build on Windows
       under either a Cygwin or MSYS environment using a recent, Windows-
       native, generic ARM EABI GCC toolchain (such as the CodeSourcery
       toolchain).  Both the build environment and the toolchain
       selection can easily be changed by reconfiguring:

       CONFIG_HOST_WINDOWS=y                   : Windows operating system
       CONFIG_WINDOWS_CYGWIN=y                 : POSIX environment under windows
       CONFIG_ARMV7A_TOOLCHAIN_CODESOURCERYW=y : CodeSourcery for Windows

       If you are running on Linux, make *certain* that you have
       CONFIG_HOST_LINUX=y *before* the first make or you will create a
       corrupt configuration that may not be easy to recover from. See
       the warning in the section "Information Common to All Configurations"
       for further information.

    3. This configuration executes out of CS0 NOR flash and can only
       be loaded via SAM-BA.  The are the relevant configuration options
       are provided above in the section entitled "NOR FLASH Support".

    4. This configuration has support for NSH built-in applications enabled.
       However, no built-in applications are selected in the base configuration.

    5. Data resides in ISRAM, but can be moved to SDRAM as described above
       under "SDRAM Data Configuration."

    6. This configuration has support for the FAT file system built in.  However,
       by default, there are no block drivers initialized.  The FAT file system can
       still be used to create RAM disks.

    7. SDRAM support can be enabled by modifying your NuttX configuration as
       described above in the paragraph entitle "SDRAM Support"

    8. The Embest or Ronetix CPU module includes an Atmel AT25DF321A,
       32-megabit, 2.7-volt SPI serial flash.  Support for that serial
       FLASH can be enabled by modifying the NuttX configuration as
       described above in the paragraph entitled "AT25 Serial FLASH".

    9. Enabling HSMCI support. The SAMA5D3x-EK provides a two SD memory card
       slots:  (1) a full size SD card slot (J7 labeled MCI0), and (2) a
       microSD memory card slot (J6 labeled MCI1).  The full size SD card
       slot connects via HSMCI0; the microSD connects vi HSMCI1.  Support
       for both SD slots can be enabled with the settings provided in the
       paragraph entitled "HSMCI Card Slots" above.

    10. Support the USB low-, high- and full-speed OHCI host driver can be enabled
        by changing the NuttX configuration file as described in the section
        entitled "USB High-Speed Host" above.

    11. Support the USB high-speed USB device driver (UDPHS) can be enabled
        by changing the NuttX configuration file as described above in the
        section entitled "USB High-Speed Device."

    12. AT24 Serial EEPROM. A AT24C512 Serial EEPPROM was used for tested
        I2C.  There is, however, no AT24 EEPROM on board the SAMA5D3x-EK:
        The  serial EEPROM was mounted on an external adaptor board and
        connected to the SAMA5D3x-EK thusly.  See the section above entitle
        "AT24 Serial EEPROM" for further information.

    13. I2C Tool. NuttX supports an I2C tool at apps/system/i2c that can be
        used to peek and poke I2C devices.  See the discussion above under
        "I2C Tool" for detailed configuration settings.

    14. Networking support via the can be added to NSH by modifying the
        configuration.  See the "Networking" section above for detailed
        configuration settings.

    15. You can enable the touchscreen and a touchscreen by following the
        configuration instrcutions in the section entitled "Touchscreen
        Testing" above.

    16. The Real Time Clock/Calendar RTC) may be enabled by reconfiguring NuttX.
        See the section entitled "RTC" above for detailed configuration settings.

    17. This example can be configured to exercise the watchdog timer test
        (apps/examples/watchdog).  See the detailed configuration settings in
        the section entitled "Watchdog Timer" above.

    18. This example can be configured to enable the SAMA5 TRNG peripheral so
        that it provides /dev/random.  See the section entitled "TRNG and
        /dev/random" above for detailed configuration information.

    19. See also the sections above for additional configuration options:
        "AT24 Serial EEPROM", "CAN Usage", "SAMA5 ADC Support", "SAMA5 PWM
        Support", "OV2640 Camera Interface", "I2S Audio Support"

    STATUS:
       See the To-Do list below

      I2C
      2013-9-12:  I have been unsuccessful getting the external serial
        AT24 EEPROM to work.  I am pretty sure that this is a problem with
        my external AT24 board (the TWI0 bus hangs when the AT24 is plugged
        in).  I will skip the AT24 integration since it is not on the critical
        path at the moment.
      2013-9-12:  The I2C tool, however, seems to work well.  It succesfully
        enumerates the devices on the bus and successfully exchanges a few
        commands.  The real test of the come later when a real I2C device is
        integrated.

  nx:

    A simple test using the NuttX graphics system (NX) that has been used to
    verify the SAMA5D3x-EK TFT LCD.  This test case focuses on general
    window controls, movement, mouse and keyboard input.  It requires no
    user interaction.

  nxwm:

    This is a special configuration setup for the NxWM window manager
    UnitTest.  It integrates support for both the SAMA5 LCDC and the
    SAMA5 ADC touchscreen controller and provides a more advance
    graphics demo. It provides an interactive windowing experience.

    The NxWM window manager is a tiny window manager tailored for use
    with smaller LCDs.  It supports a toolchain, a start window, and
    multiple application windows.  However, to make the best use of
    the visible LCD space, only one application window is visible at
    at time.

    The NxWM window manager can be found here:

      nuttx-git/NxWidgets/nxwm

    The NxWM unit test can be found at:

      nuttx-git/NxWidgets/UnitTests/nxwm

    Documentation for installing the NxWM unit test can be found here:

      nuttx-git/NxWidgets/UnitTests/README.txt

    Here is the quick summary of the build steps.  These steps assume that
    you have the entire NuttX GIT in some directory ~/nuttx-git.  You may
    have these components installed elsewhere.  In that case, you will need
    to adjust all of the paths in the following accordingly:

    1. Intall the nxwm configuration

       $ cd ~/nuttx-git/nuttx/tools
       $ ./configure.sh sama5d3x-ek/nxwm

    2. Make the build context (only)

       $ cd ..
       $ . ./setenv.sh
       $ make context
       ...

       NOTE: the use of the setenv.sh file is optional.  All that it will
       do is to adjust your PATH variable so that the build system can find
       your tools.  If you use it, you will most likely need to modify the
       script so that it has the correct path to your tool binaries
       directory.

    3. Install the nxwm unit test

       $ cd ~/nuttx-git/NxWidgets
       $ tools/install.sh ~/nuttx-git/apps nxwm
       Creating symbolic link
        - To ~/nuttx-git/NxWidgets/UnitTests/nxwm
        - At ~/nuttx-git/apps/external

    4. Build the NxWidgets library

       $ cd ~/nuttx-git/NxWidgets/libnxwidgets
       $ make TOPDIR=~/nuttx-git/nuttx
       ...

    5. Build the NxWM library

       $ cd ~/nuttx-git/NxWidgets/nxwm
       $ make TOPDIR=~/nuttx-git/nuttx
       ...

    6. Built NuttX with the installed unit test as the application

       $ cd ~/nuttx-git/nuttx
       $ make

    STATUS:
    See the To-Do list below

    2013-10-18.  This example kind of works, but there are still far too
    many outstanding issues:

    a) It runs of the SAMA5D31 and SAMA5D34, but not on the SAMA5D33.  This
       board is from a different manufacturer and there may be some SDRAM-
       related issues?
    b) There may be an SDRAM noise issue on the SAMA5D31 and SAMA5D34.
       I suspect that the SDRAM setup is non-optimal.  The symptom is that
       writing into frame buffer (in SDRAM) occasionally corrupts the DMA
       descriptors (also in SDRAM)  When the bad DMA descriptors are
       fetched, the channel shuts down and the display goes black.  This
       problem could also be cause by a bad write outside of the framebuffer
       and, in fact, putting a guard band around the framebuffers seems to
       eliminate the problem.
    c) There are some occasional start up issues.  It appears that the LCDC
       is programed incorrectly and groups of pixels in the images are
       reversed (producing an odd serrated look to the images).
    d) I think that there may be more issues if GRAPHICS and INPUT debug is
       off.  I have not tested with DEBUG off.
    e) The biggest problem is the touchscreen accuracy.  The touchscreen
       seems stable during calibration, but the first thing that this
       example requires is a touch in the far, far, upper left corner of
       the display.  In that region, I cannot get reliable touch measurements
       and so I cannot get past the opening display.
    f) The NxWM example was designed tiny displays.  On this large 800x480
       display, the icons are too tiny to be usable.  I have created a large
       320x320 logo for the opening screen and added image scaling to expand
       the images in the taskbar.  The expanded images are not great.  If I
       ever get past the opening screen, the same problems will exist in the
       application toolbar and in the start winow.  These icons are not yet
       scaled.

    Bottom line:  Not ready for prime time.

  ov2640:

    A test of the SAMA5 ISI using an OV2640 camera.

To-Do List
==========

1) Currently the SAMA5Dx is running at 396MHz in these configurations.  This
   is because the timing for the PLLs, NOR FLASH, and SDRAM came from the
   Atmel NoOS sample code which runs at that rate.  The SAMA5Dx is capable
   of running at 528MHz, however.  The setup for that configuration exists
   in the Bareboard assembly language setup and should be incorporated.

2) Most of these configurations execute from NOR FLASH. I have been unable
   to execute these configurations from NOR FLASH by closing the BMS jumper
   (J9).  As far as I can tell, this jumper does nothing on my board???  I
   have been using the norboot configuration to start the program in NOR
   FLASH (see just above).  See "Creating and Using NORBOOT" above.

3) Neither USB OHCI nor EHCI support Isochronous endpoints.  Interrupt
   endpoint support in the EHCI driver is untested (but works in similar
   EHCI drivers).

4) HSCMI TX DMA support is currently commented out.

5) I believe that there is an issue when the internal AT25 FLASH is
   formatted by NuttX.  That format works fine with Linux, but does not
   appear to work with Windows.  Reformatting on Windows can resolve this.
   NOTE:  This is not a SAMA5Dx issue.

   UPDATE: Two important bugs were recently fixed in the NuttX FAT
   formatting function (mkfatfs).  It is likely that these fixes will
   eliminate this issue, but that has not yet been verified.

6) CAN testing has not yet been performed due to issues with cabling.  I
   just do not have a good test bed (or sufficient CAN knowledge) for
   good CAN testing.

7) The NxWM example does not work well.  This example was designed to work
   with much smaller displays and does not look good or work well with the
   SAMA5Dx-EKs 800x480 display.  See above for details.

8) There are lots of LCDC hardware features that are not tested with NuttX.
   The simple NuttX graphics system does not have support for all of the
   layers and other features of the LCDC.

9) I have a Camera, but there is still no ISI driver.  I am not sure what to
   do with the camera.  NuttX needs something like V4L to provide the
   definition for what a camera driver is supposed to do.

   I will probably develop a test harness for ISI, but it is of only
   minimal value with no OS infrastructure to deal with images and video.

10) GMAC has only been tested on a 10/100Base-T network.  I don't have a
    1000Base-T network to support additional testing.
