README
^^^^^^

This README discusses issues unique to NuttX configurations for the
Atmel SAM3U-EK development board.

Contents
^^^^^^^^

  - Development Environment
  - GNU Toolchain Options
  - IDEs
  - NuttX buildroot Toolchain
  - LEDs
  - SAM3U-EK-specific Configuration Options
  - Configurations

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 CodeSourcery GNU toolchain,
  2. The devkitARM GNU toolchain, ok
  4. The NuttX buildroot Toolchain (see below).

  All testing has been conducted using the NuttX buildroot toolchain.  However,
  the make system is setup to default to use the devkitARM toolchain.  To use
  the CodeSourcery, devkitARM or Raisonance GNU toolchain, you simply need to
  add one of the following configuration options to your .config (or defconfig)
  file:

    CONFIG_SAM3U_CODESOURCERYW=y  : CodeSourcery under Windows
    CONFIG_SAM3U_CODESOURCERYL=y  : CodeSourcery under Linux
    CONFIG_SAM3U_DEVKITARM=y      : devkitARM under Windows
    CONFIG_SAM3U_BUILDROOT=y	  : NuttX buildroot under Linux or Cygwin (default)

  If you are not using CONFIG_SAM3U_BUILDROOT, 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), devkitARM, and Raisonance 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 not 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.

     Support has been added for making dependencies with the windows-native toolchains.
     That support can be enabled by modifying your Make.defs file as follows:

    -  MKDEP                = $(TOPDIR)/tools/mknulldeps.sh
    +  MKDEP                = $(TOPDIR)/tools/mkdeps.sh --winpaths "$(TOPDIR)"

     If you have problems with the dependency build (for example, if you are not
     building on C:), then you may need to modify tools/mkdeps.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 (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/sam3u,
     arch/arm/src/common, arch/arm/src/cortexm3, 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/sam3u/sam3u_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 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/project/showfiles.php?group_id=189573).
  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 sam3u-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-4.3.3 .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
  detailed PLUS some special instructions that you will need to follow if you are
  building a Cortex-M3 toolchain for Cygwin under Windows.

LEDs
^^^^

The SAM3U-EK board has four LEDs labeled LD1, LD2, LD3 and LD4 on the
the board.  Usage of these LEDs is defined in include/board.h and src/up_leds.c.
They are encoded as follows:

	SYMBOL				Meaning		LED0*	LED1	LED2
	-------------------	-----------------------	-------	-------	-------
	LED_STARTED		NuttX has been started	OFF	OFF	OFF
	LED_HEAPALLOCATE	Heap has been allocated	OFF	OFF	ON
	LED_IRQSENABLED		Interrupts enabled	OFF	ON	OFF
	LED_STACKCREATED	Idle stack created	OFF	ON	ON
	LED_INIRQ		In an interrupt**	N/C	FLASH   N/C
	LED_SIGNAL		In a signal handler***  N/C	N/C	FLASH
	LED_ASSERTION		An assertion failed	FLASH	N/C	N/C
	LED_PANIC		The system has crashed	FLASH	N/C	N/C

  * If LED1 and LED2 are statically on, then NuttX probably failed to boot
    and these LEDs will give you some indication of where the failure was
 ** The normal state is LED0=OFF, LED2=ON and LED1 faintly glowing.  This faint
    glow is because of timer interupts that result in the LED being illuminated
    on a small proportion of the time.
*** LED2 may also flicker normally if signals are processed.

SAM3U-EK-specific 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_CORTEXM3=y

	CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory

	   CONFIG_ARCH_CHIP=sam3u

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

	   CONFIG_ARCH_CHIP_AT91SAM3U4

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

	   CONFIG_ARCH_BOARD=sam3u_ek (for the SAM3U-EK development board)

	CONFIG_ARCH_BOARD_name - For use in C code

	   CONFIG_ARCH_BOARD_SAM3UEK=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_DRAM_SIZE - Describes the installed DRAM (SRAM in this case):

	   CONFIG_DRAM_SIZE=0x0000c000 (48Kb)

	CONFIG_DRAM_START - The start address of installed DRAM

	   CONFIG_DRAM_START=0x20000000

	CONFIG_DRAM_END - Last address+1 of installed RAM

	   CONFIG_DRAM_END=(CONFIG_DRAM_START+CONFIG_DRAM_SIZE)

	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 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.

  Individual subsystems can be enabled:

	CONFIG_SAM3U_DMA
	CONFIG_SAM3U_NAND
	CONFIG_SAM3U_HSMCI
	CONFIG_SAM3U_UART
	CONFIG_SAM3U_USART0
	CONFIG_SAM3U_USART1
	CONFIG_SAM3U_USART2
	CONFIG_SAM3U_USART3

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

	CONFIG_GPIOA_IRQ
	CONFIG_GPIOB_IRQ
	CONFIG_GPIOC_IRQ
	CONFIG_USART0_ISUART
	CONFIG_USART1_ISUART
	CONFIG_USART2_ISUART
	CONFIG_USART3_ISUART

  AT91SAM3U 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

Configurations
^^^^^^^^^^^^^^

Each SAM3U-EK configuration is maintained in a sudirectory and
can be selected as follow:

	cd tools
	./configure.sh sam3u-ek/<subdir>
	cd -
	. ./setenv.sh

Before sourcing the setenv.sh file above, you should examine it and perform
edits as necessary so that BUILDROOT_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:

  knsh:
    This is identical to the nsh configuration below except that NuttX
    is built as a kernel-mode, monolithic module and the user applications
    are built separately.  This build requires a special make command; not
    just 'make' but make with the following two arguments:

	    make pass1 pass2

    This is required because in the normal case (just 'make'), make will
    create all dependencies then execute the pass1 and pass2 targets.  But
    this example, pass2 depends on auto-generatd files produced during pass1.
    This specall make command ('make pass1 pass2') will make the dependencies
    separately for each pass.

	At there end of the build, there four files will top-level build
	directory:

	nuttx_user.elf	- The pass1 ELF file
	nuttx			- The pass2 ELF file
	nuttx_user.ihx	- The pass1 Intel HEX format file
	nuttx.ihx		- The pass2 Intel HEX file

	The J-Link program will except files in .hex, .mot, .srec, and .bin
	formats.

  nsh:
    Configures the NuttShell (nsh) located at examples/nsh.  The
    Configuration enables both the serial and telnetd NSH interfaces.

  nx
    Configures to use examples/nx using the HX834x LCD hardwar on
    the SAM3U-EK development board.

  ostest:
    This configuration directory, performs a simple OS test using
    examples/ostest.  By default, this project assumes that you are
    using the DFU bootloader.

