README
======

README for NuttX port to the Tiva TM4C123G LaunchPad.  The Tiva TM4C123G
LaunchPad Evaluation Board is a low-cost evaluation platform for ARM®
Cortex™-M4F-based microcontrollers from Texas Instruments.

Contents
========

  On-Board GPIO Usage
  Development Environment
  GNU Toolchain Options
  IDEs
  NuttX EABI "buildroot" Toolchain
  NuttX OABI "buildroot" Toolchain
  NXFLAT Toolchain
  LEDs
  Serial Console
  USB Device Controller Functions
  AT24 Serial EEPROM
  I2C Tool
  Using OpenOCD and GDB with an FT2232 JTAG emulator
  TM4C123G LaunchPad Configuration Options
  Configurations

On-Board GPIO Usage
===================

PIN SIGNAL(S)                                LanchPad Function
--- ---------------------------------------- ---------------------------------------
 17 PA0/U0RX                                 DEBUG/VCOM, Virtual COM port receive
 18 PA1/U0TX                                 DEBUG/VCOM, Virtual COM port transmit
 19 PA2/SSIOCLK                              GPIO, J2 pin 10
 20 PA3/SSIOFSS                              GPIO, J2 pin 9
 21 PA4/SSIORX                               GPIO, J2 pin 8
 22 PA5/SSIOTX                               GPIO, J1 pin 8
 23 PA6/I2CLSCL                              GPIO, J1 pin 9
 24 PA7/I2CLSDA                              GPIO, J1 pin 10

 45 PB0/T2CCP0/U1Rx                          GPIO, J1 pin 3
 46 PB1/T2CCP1/U1Tx                          GPIO, J1 pin 4
 47 PB2/I2C0SCL/T3CCP0                       GPIO, J2 pin 2
 48 PB3/I2C0SDA/T3CCP1                       GPIO, J4 pin 3
 58 PB4/AIN10/CAN0Rx/SSI2CLK/T1CCP0          GPIO, J1 pin 7
 57 PB5/AIN11/CAN0Tx/SSI2FSS/T1CCP1          GPIO, J1 pin 2
 01 PB6/SSI2RX/T0CCP0                        Connects to PD0 via resistor, GPIO, J2 pin 7
 04 PB7/SSI2TX/T0CCP1                        Connects to PD1 via resistor, GPIO, J2 pin 6

 52 PC0/SWCLK/T4CCP0/TCK                     DEBUG/VCOM
 51 PC1/SWDIO/T4CCP1/TMS                     DEBUG/VCOM
 50 PC2/T5CCP0/TDI                           DEBUG/VCOM
 49 PC3/SWO/T5CCP1/TDO                       DEBUG/VCOM
 16 PC4/C1-/U1RTS/U1RX/U4RX/WT0CCP0          GPIO, J4 pin 4
 15 PC5/C1+/U1CTS/U1TX/U4TX/WT0CCP1          GPIO, J4 pin 5
 14 PC6/C0+/U3RX/WT1CCP0                     GPIO, J4 pin 6
 13 PC7/C0-/U3TX/WT1CCP1                     GPIO, J4 pin 7

 61 PD0/AIN7/I2C3SCL/SSI1CLK/SSI3CLKWT2CCP0  Connects to PB6 via resistor, GPIO, J3 pin 3
 62 PD1/AIN6/I2C3SDA/SSI1Fss/SSI3Fss/WT2CCP1 Connects to PB7 via resistor, GPIO, J3 Pin 4
 63 PD2/AIN5/SSI1RX/SSI3RX/WT3CCP0           GPIO, J3 pin 5
 64 PD3/AIN4/SSI1TX/SSI3TX/WT3CCP1           GPIO, J3 pin 6
 43 PD4/U6RX/USB0DM/WT4CCP0                  USB_DM
 44 PD5/U6TX/USB0DP/WT4CCP1                  USB_DP
 53 PD6/U2RX/WT5CCP0                         GPIO, J4 pin 8
 10 PD7/NMI/U2TX/WT5CCP1                     +USB_VBUS, GPIO, J4 pin 9
                                             Used for VBUS detection when
                                             configured as a self-powered USB
                                             Device

 09 PE0/AIN3/U7RX                            GPIO, J2 pin 3
 08 PE1/AIN2/U7TX                            GPIO, J3 pin 7
 07 PE2/AIN1                                 GPIO, J3 pin 8
 06 PE3/AIN0                                 GPIO, J3 pin 9
 59 PE4/AIN9/CAN0RX/I2C2SCL/U5RX             GPIO, J1 pin 5
 60 PE5/AIN8/CAN0TX/I2C2SDA/U5TX             GPIO, J1 pin 6

 28 PF0/C0O/CAN0RX/NMI/SSI1RX/T0CCP0/U1RTS   USR_SW2 (Low when pressed), GPIO, J2 pin 4
 29 PF1/C1O/SSI1TX/T0CCP1/TRD1/U1CTS         LED_R, GPIO, J3 pin 10
 30 PF2/SSI1CLK/T1CCP0/TRD0                  LED_B, GPIO, J4 pin 1
 31 PF3/CAN0TX/SSI1FSS/T1CCP1/TRCLK          LED_G, GPIO, J4 pin 2
 05 PF4/T2CCP0                               USR_SW1 (Low when pressed), GPIO, J4 pin 10

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

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

  A AT24C512 Serial EEPPROM was used for tested I2C.  There are no I2C
  devices on-board the Launchpad, but an external serial EEPROM module 
  module was used.

  The Serial EEPROM was mounted on an external adaptor board and connected
  to the LaunchPad thusly:

    - VCC  J1 pin 1  3.3V
           J3 pin 1  5.0V
    - GND  J2 pin 1  GND
           J3 pin 2  GND
    - PB2  J2 pin 2  SCL
    - PB3  J4 pin 3  SDA

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

  The following configuration settings were used:

    System Type -> Tiva/Stellaris Peripheral Support
      CONFIG_TIVA_I2C0=y                    : Enable I2C

    System Type -> I2C device driver options
      TIVA_I2C_FREQUENCY=100000             : Select an I2C 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_TM4C123G_LAUNCHPAD_AT24_BLOCKMOUNT=y   : Mounts AT24 for NSH
      CONFIG_TM4C123G_LAUNCHPAD_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

  STATUS:
  2014-12-12:  I was unsuccessful getting my AT24 module to work on the TM4C123G
    LaunchPad.  I was unable to successuflly communication with the AT24 via
    I2C.  I did verify I2C using the I2C tool and other I2C devices and I now
    belive that my AT24 module is not fully functional.

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 can be enabled by setting the
  following:

    System Type -> TIVA Peripheral Support
      CONFIG_TIVA_I2C0=y                   : Enable I2C0
      CONFIG_TIVA_I2C1=y                   : Enable I2C1
      CONFIG_TIVA_I2C2=y                   : Enable I2C2
      ...

    System Type -> I2C device driver options
      CONFIG_TIVA_I2C0_FREQUENCY=100000    : Select an I2C0 frequency
      CONFIG_TIVA_I2C1_FREQUENCY=100000    : Select an I2C1 frequency
      CONFIG_TIVA_I2C2_FREQUENCY=100000    : Select an I2C2 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               : I2C0 has the minimum bus number 0
      CONFIG_I2CTOOL_MAXBUS=2               : I2C2 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 command can be used to list all devices
    responding on I2C0 (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>

    NOTE:  This is output from a different board and shows I2C
    devices responding at addresses 0x1a, 0x39, 0x3d, and 0x60.

Using OpenOCD and GDB with an FT2232 JTAG emulator
==================================================

  Building OpenOCD under Cygwin:

    Refer to configs/olimex-lpc1766stk/README.txt

  Installing OpenOCD in Linux:

      sudo apt-get install openocd

    As of this writing, there is no support for the tm4c123g in the package
    above. You will have to build openocd from its source (as of this writing
    the latest commit was b9b4bd1a6410ff1b2885d9c2abe16a4ae7cb885f):

      git clone http://git.code.sf.net/p/openocd/code openocd
      cd openocd

    Then, add the patches provided by http://openocd.zylin.com/922:

      git fetch http://openocd.zylin.com/openocd refs/changes/22/922/14 && git checkout FETCH_HEAD
      ./bootstrap
      ./configure --enable-maintainer-mode --enable-ti-icdi
      make
      sudo make install

    For additional help, see http://processors.wiki.ti.com/index.php/Tiva_Launchpad_with_OpenOCD_and_Linux

  Helper Scripts.

    I have been using the on-board In-Circuit Debug Interface (ICDI) interface.
    OpenOCD requires a configuration file.  I keep the one I used last here:

      configs/tm4c123g-launchpad/tools/tm4c123g-launchpad.cfg

    However, the "correct" configuration script to use with OpenOCD may
    change as the features of OpenOCD evolve.  So you should at least
    compare that tm4c123g-launchpad.cfg file with configuration files in
    /usr/share/openocd/scripts.  As of this writing, the configuration
    files of interest were:

      /usr/local/share/openocd/scripts/board/ek-tm4c123gxl.cfg
      /usr/local/share/openocd/scripts/interface/ti-icdi.cfg
      /usr/local/share/openocd/scripts/target/stellaris_icdi.cfg

    There is also a script on the tools/ directory that I use to start
    the OpenOCD daemon on my system called oocd.sh.  That script will
    probably require some modifications to work in another environment:

    - Possibly the value of OPENOCD_PATH and TARGET_PATH
    - It assumes that the correct script to use is the one at
      configs/tm4c123g-launchpad/tools/tm4c123g-launchpad.cfg

  Starting OpenOCD

    If you are in the top-level NuttX build directlory then you should
    be able to start the OpenOCD daemon like:

      oocd.sh $PWD

    The relative path to the oocd.sh script is configs/tm4c123g-launchpad/tools,
    but that should have been added to your PATH variable when you sourced
    the setenv.sh script.

    Note that OpenOCD needs to be run with administrator privileges in
    some environments (sudo).

  Connecting GDB

    Once the OpenOCD daemon has been started, you can connect to it via
    GDB using the following GDB command:

      arm-nuttx-elf-gdb
      (gdb) target remote localhost:3333

    NOTE:  The name of your GDB program may differ.  For example, with the
    CodeSourcery toolchain, the ARM GDB would be called arm-none-eabi-gdb.

    After starting GDB, you can load the NuttX ELF file:

      (gdb) symbol-file nuttx
      (gdb) monitor reset
      (gdb) monitor halt
      (gdb) load nuttx

    NOTES:
    1. Loading the symbol-file is only useful if you have built NuttX to
       include debug symbols (by setting CONFIG_DEBUG_SYMBOLS=y in the
       .config file).
    2. The MCU must be halted prior to loading code using 'mon reset'
       as described below.

    OpenOCD will support several special 'monitor' commands.  These
    GDB commands will send comments to the OpenOCD monitor.  Here
    are a couple that you will need to use:

     (gdb) monitor reset
     (gdb) monitor halt

    NOTES:
    1. The MCU must be halted using 'mon halt' prior to loading code.
    2. Reset will restart the processor after loading code.
    3. The 'monitor' command can be abbreviated as just 'mon'.

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

  Either Linux or Cygwin on Windows can be used for the development environment.
  The source has been built only using the GNU toolchain (see below).  Other
  toolchains will likely cause problems. Testing was performed using the Cygwin
  environment.

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

  The NuttX make system has been modified to support the following different
  toolchain options.

  1. The NuttX buildroot Toolchain (default, see below),
  2. The CodeSourcery GNU toolchain,
  3. The devkitARM GNU toolchain,
  4. The Atollic toolchain, or
  5. The Code Red toolchain

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

    CONFIG_ARMV7M_TOOLCHAIN_BUILDROOT=y      : NuttX buildroot under Linux or Cygwin (default)
    CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYW=y  : CodeSourcery under Windows or Cygwin
    CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYL=y  : CodeSourcery under Linux
    CONFIG_ARMV7M_TOOLCHAIN_DEVKITARM=y      : The Atollic toolchain under Windows or Cygwin
    CONFIG_ARMV7M_TOOLCHAIN_CODEREDW=y       : The Code Red toolchain under Windows
    CONFIG_ARMV7M_TOOLCHAIN_CODEREDL=y       : The Code Red toolchain under Linux

    CONFIG_ARMV7M_OABI_TOOLCHAIN=y           : If you use an older, OABI buildroot toolchain

  If you change the default toolchain, then you may also have to modify the PATH in
  the setenv.h file if your make cannot find the tools.

  NOTE: the CodeSourcery (for Windows), Atollic, devkitARM, and Code Red (for Windows)
  toolchains are Windows native toolchains.  The CodeSourcey (for Linux) and NuttX
  buildroot toolchains are Cygwin and/or Linux 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 pathes which do not
     work with the Cygwin make.

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

  NOTE 1: The CodeSourcery toolchain (2009q1) does 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.

  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 paths:  You will need include/, arch/arm/src/tiva,
     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/tiva/tiva_vectors.S.

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 tm4c123g-launchpad/<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:

  1. When building the buildroot toolchain, either (1) modify the cortexm3-eabi-defconfig-4.6.3
     configuration to use EABI (using 'make menuconfig'), or (2) use an exising OABI
     configuration such as cortexm3-defconfig-4.3.3

  2. Modify the Make.defs file to use the OABI conventions:

    +CROSSDEV = arm-nuttx-elf-
    +ARCHCPUFLAGS = -mtune=cortex-m3 -march=armv7-m -mfloat-abi=soft
    +NXFLATLDFLAGS2 = $(NXFLATLDFLAGS1) -T$(TOPDIR)/binfmt/libnxflat/gnu-nxflat-gotoff.ld -no-check-sections
    -CROSSDEV = arm-nuttx-eabi-
    -ARCHCPUFLAGS = -mcpu=cortex-m3 -mthumb -mfloat-abi=soft
    -NXFLATLDFLAGS2 = $(NXFLATLDFLAGS1) -T$(TOPDIR)/binfmt/libnxflat/gnu-nxflat-pcrel.ld -no-check-sections

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 tm4c123g-launchpad/<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 builtNXFLAT binaries.

LEDs
====
  The TM4C123G has a single RGB LED.  If CONFIG_ARCH_LEDS is defined, then
  support for the LaunchPad LEDs will be included in the build.  See:

  - configs/tm4c123g-launchpad/include/board.h - Defines LED constants, types and
    prototypes the LED interface functions.

  - configs/tm4c123g-launchpad/src/tm4c123g-launchpad.h - GPIO settings for the LEDs.

  - configs/tm4c123g-launchpad/src/up_leds.c - LED control logic.

  OFF:
  - OFF means that the OS is still initializing. Initialization is very fast so
    if you see this at all, it probably means that the system is hanging up
    somewhere in the initialization phases.

  GREEN or GREEN-ish
  - This means that the OS completed initialization.

  Bluish:
  - Whenever and interrupt or signal handler is entered, the BLUE LED is
    illuminated and extinguished when the interrupt or signal handler exits.
    This will add a BLUE-ish tinge to the LED.

  Redish:
  - If a recovered assertion occurs, the RED component will be illuminated
    briefly while the assertion is handled.  You will probably never see this.

  Flashing RED:
  - In the event of a fatal crash, the BLUE and GREEN components will be
    extinguished and the RED component will FLASH at a 2Hz rate.

Serial Console
==============

  By default, all configurations use UART0 which connects to the USB VCOM
  on the DEBUG port on the TM4C123G LaunchPad:

    UART0 RX - PA.0
    UART0 TX - PA.1

  However, if you use an external RS232 driver, then other options are
  available.  UART1 has option pin settings and flow control capabilities
  that are not available with the other UARTS::

    UART1 RX - PB.0 or PC.4 (Need disambiguation in board.h)
    UART1 TX - PB.1 or PC.5 ("  " "            " "" "     ")

    UART1_RTS - PF.0 or PC.4
    UART1_CTS - PF.1 or PC.5

  NOTE: board.h currently selects PB.0, PB.1, PF.0 and PF.1 for UART1, but
  that can be changed by editting board.h

  UART2-5, 7 are also available, UART2 is not recommended because it shares
  some pin usage with USB device mode.  UART6 is not available because its
  only RX/TX pin options are dedicated to USB support.

    UART2 RX - PD.6
    UART2 TX - PD.7 (Also used for USB VBUS detection)

    UART3 RX - PC.6
    UART3 TX - PC.7

    UART4 RX - PC.4
    UART4 TX - PC.5

    UART5 RX - PE.4
    UART5 TX - PE.5

    UART6 RX - PD.4, Not available.  Dedicated for USB_DM
    UART6 TX - PD.5, Not available.  Dedicated for USB_DP

    UART7 RX - PE.0
    UART7 TX - PE.1

USB Device Controller Functions
===============================

  Device Overview

    An FT2232 device from Future Technology Devices International Ltd manages
    USB-to-serial conversion. The FT2232 is factory configured by Luminary
    Micro to implement a JTAG/SWD port (synchronous serial) on channel A and
    a Virtual COM Port (VCP) on channel B. This feature allows two simultaneous
    communications links between the host computer and the target device using
    a single USB cable. Separate Windows drivers for each function are provided
    on the Documentation and Software CD.

  Debugging with JTAG/SWD

    The FT2232 USB device performs JTAG/SWD serial operations under the control
    of the debugger or the Luminary Flash Programmer.  It also operate as an
    In-Circuit Debugger Interface (ICDI), allowing debugging of any external
    target board.  Debugging modes:

    MODE DEBUG FUNCTION       USE                         SELECTED BY
    1    Internal ICDI        Debug on-board TM4C123G     Default Mode
                              microcontroller over USB
                              interface.
    2    ICDI out to JTAG/SWD The EVB is used as a USB    Connecting to an external
         header               to SWD/JTAG interface to    target and starting debug
                              an external target.         software. The red Debug Out
                                                          LED will be ON.
    3    In from JTAG/SWD     For users who prefer an     Connecting an external
         header               external debug interface    debugger to the JTAG/SWD
                              (ULINK, JLINK, etc.) with   header.
                              the EVB.

  Virtual COM Port

    The Virtual COM Port (VCP) allows Windows applications (such as HyperTerminal)
    to communicate with UART0 on the TM4C123G over USB. Once the FT2232 VCP
    driver is installed, Windows assigns a COM port number to the VCP channel.

TM4C123G LaunchPad 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_CORTEXM4=y

    CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory

       CONFIG_ARCH_CHIP="tiva"

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

       CONFIG_ARCH_CHIP_TM4C123GH6PMI

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

       CONFIG_ARCH_BOARD=tm4c123g-launchpad (for the TM4C123G LaunchPad)

    CONFIG_ARCH_BOARD_name - For use in C code

       CONFIG_ARCH_BOARD_TM4C123G_LAUNCHPAD

    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=0x00008000 (32Kb)

    CONFIG_RAM_START - The start address of installed DRAM

       CONFIG_RAM_START=0x20000000

    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 calibratre
       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.

  There are configurations for disabling support for interrupts GPIO ports.
  Only GPIOP and GPIOQ pins can be used as interrupting sources on the
  TM4C129x.  Additional interrupt support can be disabled if desired to
  reduce memory footprint.

    CONFIG_TIVA_GPIOP_IRQS=y
    CONFIG_TIVA_GPIOQ_IRQS=y

  TM4C123G specific device driver settings

    CONFIG_UARTn_SERIAL_CONSOLE - selects the UARTn for the
       console and ttys0 (default is the UART0).
    CONFIG_UARTn_RXBUFSIZE - Characters are buffered as received.
       This specific the size of the receive buffer
    CONFIG_UARTn_TXBUFSIZE - Characters are buffered before
       being sent.  This specific the size of the transmit buffer
    CONFIG_UARTn_BAUD - The configure BAUD of the UART.  Must be
    CONFIG_UARTn_BITS - The number of bits.  Must be either 7 or 8.
    CONFIG_UARTn_PARTIY - 0=no parity, 1=odd parity, 2=even parity
    CONFIG_UARTn_2STOP - Two stop bits

    CONFIG_TIVA_SSI0 - Select to enable support for SSI0
    CONFIG_TIVA_SSI1 - Select to enable support for SSI1
    CONFIG_SSI_POLLWAIT - Select to disable interrupt driven SSI support.
      Poll-waiting is recommended if the interrupt rate would be to
      high in the interrupt driven case.
    CONFIG_SSI_TXLIMIT - Write this many words to the Tx FIFO before
      emptying the Rx FIFO.  If the SPI frequency is high and this
      value is large, then larger values of this setting may cause
      Rx FIFO overrun errors.  Default: half of the Tx FIFO size (4).

    CONFIG_TIVA_ETHERNET - This must be set (along with CONFIG_NET)
      to build the Tiva Ethernet driver
    CONFIG_TIVA_ETHLEDS - Enable to use Ethernet LEDs on the board.
    CONFIG_TIVA_BOARDMAC - If the board-specific logic can provide
      a MAC address (via tiva_ethernetmac()), then this should be selected.
    CONFIG_TIVA_ETHHDUPLEX - Set to force half duplex operation
    CONFIG_TIVA_ETHNOAUTOCRC - Set to suppress auto-CRC generation
    CONFIG_TIVA_ETHNOPAD - Set to suppress Tx padding
    CONFIG_TIVA_MULTICAST - Set to enable multicast frames
    CONFIG_TIVA_PROMISCUOUS - Set to enable promiscuous mode
    CONFIG_TIVA_BADCRC - Set to enable bad CRC rejection.
    CONFIG_TIVA_DUMPPACKET - Dump each packet received/sent to the console.

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

Each TM4C123G LaunchPad configuration is maintained in a
sub-directory and can be selected as follow:

    cd tools
    ./configure.sh tm4c123g-launchpad/<subdir>
    cd -
    . ./setenv.sh

Where <subdir> is one of the following:

  nsh:
  ---
    Configures the NuttShell (nsh) located at apps/examples/nsh.  The
    configuration enables the serial VCOM interfaces on UART0.  Support for
    builtin applications is enabled, but in the base configuration no
    builtin applications are selected.

    NOTES:

    1. This configuration uses the mconf-based configuration tool.  To
       change this configuration 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. By default, this configuration uses the CodeSourcery toolchain
       for Windows and builds under Cygwin (or probably MSYS).  That
       can easily be reconfigured, of course.

       CONFIG_HOST_LINUX=y                 : Linux (Cygwin under Windows okay too).
       CONFIG_ARMV7M_TOOLCHAIN_BUILDROOT=y : Buildroot (arm-nuttx-elf-gcc)
       CONFIG_RAW_BINARY=y                 : Output formats: ELF and raw binary
