nuttx/configs/sam3u-ek/README.txt

README
^^^^^^

This README discusses issues unique to NuttX configurations for the Atmel
SAM3U-EK development board featuring the ATAM3U.  This board features the
ATSAM3U4E MCU running at 96MHz.

Contents
^^^^^^^^

  - Development Environment
  - GNU Toolchain Options
  - IDEs
  - NuttX EABI "buildroot" Toolchain
  - NuttX OABI "buildroot" Toolchain
  - NXFLAT Toolchain
  - AtmelStudio6.1
  - LEDs
  - Serial Console
  - 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.  To use
  the CodeSourcery, devkitARM, Atollic, or AtmelStudio GNU toolchain, you simply
  need to add one of the following configuration options to your .config (or
  defconfig) file:

    CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYW=y  : CodeSourcery under Windows
    CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYL=y  : CodeSourcery under Linux
    CONFIG_ARMV7M_TOOLCHAIN_ATOLLIC=y        : Atollic toolchain for Windos
    CONFIG_ARMV7M_TOOLCHAIN_DEVKITARM=y      : devkitARM under Windows
    CONFIG_ARMV7M_TOOLCHAIN_BUILDROOT=y      : NuttX buildroot under Linux or Cygwin (default)
    CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIL=y      : Generic GCC ARM EABI toolchain for Linux
    CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIW=y      : Generic GCC ARM EABI toolchain for Windows

  If you are not using CONFIG_ARMV7M_TOOLCHAIN_BUILDROOT, 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
  ------------------------------------

  The CodeSourcery (for Windows), Atollic, and devkitARM toolchains are
  Windows native toolchains.  The CodeSourcery (for Linux), NuttX buildroot,
  and, perhaps, the generic GCC 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 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 an IDE.

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 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-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 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-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.

AtmelStudio6.1
^^^^^^^^^^^^^^

  You can use AtmelStudio6.1 to load and debug code.

  - To load code:

    Tools -> Device Programming

    Configure the debugger and chip and you are in business.

  - To Debug Code:

    File -> Open -> Open Object File for Debugging

    Select the project name, the full path to the NuttX object (called
    just nuttx with no extension), and chip.  Take the time to resolve
    all of the source file linkages or else you will not have source
    level debug!

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.

Serial Console
^^^^^^^^^^^^^^

  By default, all of these configurations use UART0 for the NuttX serial
  console.  UART0 corresponds to the DB-9 connector labelled "UART".  This
  is a male connector and will require a female-to-female, NUL modem cable
  to connect to a PC.

  An alternate is USART1 which connects to the other DB-9 connector labeled
  "USART".  USART1 is not enabled by default unless specifically noted
  otherwise in the configuration description.  A NUL modem cable must be
  used with the port as well.

  NOTE:  One of the USART1 pins is shared with the audio CODEC.  The audio
  CODEC cannot be used of USART1 is enabled.

  By default serial console is configured for 115000, 8-bit, 1 stop bit, and
  no parity.

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="sam34"

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

       CONFIG_ARCH_CHIP_SAM34
       CONFIG_ARCH_CHIP_SAM3U
       CONFIG_ARCH_CHIP_ATSAM3U4

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

       CONFIG_RAM_SIZE=0x0000c000 (48Kb)

    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.

  Individual subsystems can be enabled:

    CONFIG_SAM34_RTC           - Real Time Clock
    CONFIG_SAM34_RTT           - Real Time Timer
    CONFIG_SAM34_WDT           - Watchdog Timer
    CONFIG_SAM34_UART0         - UART 0
    CONFIG_SAM34_SMC           - Static Memory Controller
    CONFIG_SAM34_USART0        - USART 0
    CONFIG_SAM34_USART1        - USART 1
    CONFIG_SAM34_USART2        - USART 2
    CONFIG_SAM34_USART3        - USART 3
    CONFIG_SAM34_HSMCI         - High Speed Multimedia Card Interface
    CONFIG_SAM34_TWI0          - Two-Wire Interface 0
    CONFIG_SAM34_TWI1          - Two-Wire Interface 1
    CONFIG_SAM34_SPI0           - Serial Peripheral Interface
    CONFIG_SAM34_SSC           - Synchronous Serial Controller
    CONFIG_SAM34_TC0           - Timer Counter 0
    CONFIG_SAM34_TC1           - Timer Counter 1
    CONFIG_SAM34_TC2           - Timer Counter 2
    CONFIG_SAM34_PWM           - Pulse Width Modulation Controller
    CONFIG_SAM34_ADC12B        - 12-bit ADC Controller
    CONFIG_SAM34_ADC           - 10-bit ADC Controller
    CONFIG_SAM34_DMAC0         - DMA Controller
    CONFIG_SAM34_UDPHS         - USB Device High Speed

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

    CONFIG_SAM34_GPIOA_IRQ
    CONFIG_SAM34_GPIOB_IRQ
    CONFIG_SAM34_GPIOC_IRQ
    CONFIG_USART0_ISUART
    CONFIG_USART1_ISUART
    CONFIG_USART2_ISUART
    CONFIG_USART3_ISUART
    CONFIG_SAM34_NAND          - NAND memory

  SAM3U 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

  LCD Options.  Other than the standard LCD configuration options
  (see configs/README.txt), the SAM3U-EK driver also supports:

    CONFIG_LCD_PORTRAIT - Present the display in the standard 240x320
       "Portrait" orientation.  Default:  The display is rotated to
       support a 320x240 "Landscape" orientation.

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 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.

  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. Unless otherwise stated, the configurations are setup for
     Linux (or any other POSIX environment like Cygwin under Windows):

     Build Setup:
       CONFIG_HOST_LINUX=y   : Linux or other POSIX environment

  4. All of these configurations use the older, OABI, buildroot 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_LINUX=y                 : Linux or other pure POSIX invironment
                                           : (including Cygwin)
     System Type -> Toolchain:
       CONFIG_ARMV7M_TOOLCHAIN_BUILDROOT=y : Buildroot toolchain
       CONFIG_ARMV7M_OABI_TOOLCHAIN=y      : Older, OABI toolchain

     If you want to use the Atmel GCC toolchain, for example, here are the
     steps to do so:

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

     System Type -> Toolchain:
       CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIW=y : General GCC EABI toolchain under windows

     Library Routines ->
       CONFIG_CXX_NEWLONG=n                : size_t is an unsigned int, not long

     This re-configuration should be done before making NuttX or else the
     subsequent 'make' will fail.  If you have already attempted building
     NuttX then you will have to 1) 'make distclean' to remove the old
     configuration, 2) 'cd tools; ./configure.sh sam3u-ek/ksnh' to start
     with a fresh configuration, and 3) perform the configuration changes
     above.

     Also, make sure that your PATH variable has the new path to your
     Atmel tools.  Try 'which arm-none-eabi-gcc' to make sure that you
     are selecting the right tool.  setenv.sh is available for you to
     use to set or 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.

  Configuration sub-directories
  -----------------------------

  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.  It is recommends to use a special make command;
    not just 'make' but make with the following two arguments:

        make pass1 pass2

    In the normal case (just 'make'), make will attempt to build both user-
    and kernel-mode blobs more or less interleaved.  This actual works!
    However, for me it is very confusing so I prefer the above make command:
    Make the user-space binaries first (pass1), then make the kernel-space
    binaries (pass2)

    NOTES:

    1. At the end of the build, there will be several files in the top-level
       NuttX build directory:

       PASS1:
         nuttx_user.elf    - The pass1 user-space ELF file
         nuttx_user.hex    - The pass1 Intel HEX format file (selected in defconfig)
         User.map          - Symbols in the user-space ELF file

       PASS2:
         nuttx             - The pass2 kernel-space ELF file
         nuttx.hex         - The pass2 Intel HEX file (selected in defconfig)
         System.map        - Symbols in the kernel-space ELF file

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

    2. Combining .hex files.  If you plan to use the .hex files with your
       debugger or FLASH utility, then you may need to combine the two hex
       files into a single .hex file.  Here is how you can do that.

       a. The 'tail' of the nuttx.hex file should look something like this
          (with my comments added):

            $ tail nuttx.hex
            # 00, data records
            ...
            :10 9DC0 00 01000000000800006400020100001F0004
            :10 9DD0 00 3B005A0078009700B500D400F300110151
            :08 9DE0 00 30014E016D0100008D
            # 05, Start Linear Address Record
            :04 0000 05 0800 0419 D2
            # 01, End Of File record
            :00 0000 01 FF

          Use an editor such as vi to remove the 05 and 01 records.

       b. The 'head' of the nuttx_user.hex file should look something like
          this (again with my comments added):

            $ head nuttx_user.hex
            # 04, Extended Linear Address Record
            :02 0000 04 0801 F1
            # 00, data records
            :10 8000 00 BD89 01084C800108C8110208D01102087E
            :10 8010 00 0010 00201C1000201C1000203C16002026
            :10 8020 00 4D80 01085D80010869800108ED83010829
            ...

          Nothing needs to be done here.  The nuttx_user.hex file should
          be fine.

       c. Combine the edited nuttx.hex and un-edited nuttx_user.hex
          file to produce a single combined hex file:

          $ cat nuttx.hex nuttx_user.hex >combined.hex

       Then use the combined.hex file with the to write the FLASH image.
       If you do this a lot, you will probably want to invest a little time
       to develop a tool to automate these steps.

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

    NOTES:

    1. NSH built-in applications are supported.  However, there are
       no built-in applications built with the default configuration.

       Binary Formats:
         CONFIG_BUILTIN=y                    : Enable support for built-in programs

       Applicaton Configuration:
         CONFIG_NSH_BUILTIN_APPS=y           : Enable starting apps from NSH command line

    2. This configuration has been used for verifying the touchscreen on
       on the SAM3U-EK LCD.  With these modifications, you can include the
       touchscreen test program at apps/examples/touchscreen as an NSH built-in
       application.  You can enable the touchscreen and test by modifying the
       default configuration in the following ways:

          Device Drivers
            CONFIG_SPI=y                      : Enable SPI support
            CONFIG_SPI_EXCHANGE=y             : The exchange() method is supported
            CONFIG_SPI_OWNBUS=y               : Smaller code if this is the only SPI device

            CONFIG_INPUT=y                    : Enable support for input devices
            CONFIG_INPUT_ADS7843E=y           : Enable support for the XPT2046
            CONFIG_ADS7843E_SPIDEV=2          : Use SPI CS 2 for communication
            CONFIG_ADS7843E_SPIMODE=0         : Use SPI mode 0
            CONFIG_ADS7843E_FREQUENCY=1000000 : SPI BAUD 1MHz
            CONFIG_ADS7843E_SWAPXY=y          : If landscpe orientation
            CONFIG_ADS7843E_THRESHX=51        : These will probably need to be tuned
            CONFIG_ADS7843E_THRESHY=39

          System Type -> Peripherals:
            CONFIG_SAM34_SPI0=y               : Enable support for SPI

          System Type:
            CONFIG_SAM34_GPIO_IRQ=y           : GPIO interrupt support
            CONFIG_SAM34_GPIOA_IRQ=y          : Enable GPIO interrupts from port A

          RTOS Features:
            CONFIG_DISABLE_SIGNALS=n          : Signals are required

          Library Support:
            CONFIG_SCHED_WORKQUEUE=y          : Work queue support required

          Applicaton Configuration:
            CONFIG_EXAMPLES_TOUCHSCREEN=y     : Enable the touchscreen built-int test

          Defaults should be okay for related touchscreen settings.  Touchscreen
          debug output on UART0 can be enabled with:

          Build Setup:
            CONFIG_DEBUG=y                    : Enable debug features
            CONFIG_DEBUG_VERBOSE=y            : Enable verbose debug output
            CONFIG_DEBUG_INPUT=y              : Enable debug output from input devices

    3. Enabling HSMCI support. The SAM3U-KE provides a an SD memory card
       slot.  Support for the SD slot can be enabled with the following
       settings:

       System Type->ATSAM3/4 Peripheral Support
         CONFIG_SAM34_HSMCI=y                 : Enable HSMCI support
         CONFIG_SAM34_DMAC0=y                 : DMAC support is needed by HSMCI

       System Type
         CONFIG_SAM34_GPIO_IRQ=y              : PIO interrupts needed
         CONFIG_SAM34_GPIOA_IRQ=y             : Card detect pin is on PIOA

       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_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

    STATUS:
      2013-6-28: The touchscreen is functional.
      2013-6-29: Hmmm... but there appear to be conditions when the
        touchscreen driver locks up.  Looks like some issue with
        managing the interrupts.
      2013-6-30:  Those lock-ups appear to be due to poorly placed
        debug output statements.  If you do not enable debug output,
        the touchscreen is rock-solid.
      2013-8-10:  Added the comments above above enabling HSMCI memory
        card support and verified that the configuration builds without
        error.  However, that configuration has not yet been tested (and
        is may even be incomplete).

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

  nxwm:
    This is a special configuration setup for the NxWM window manager
    UnitTest.  It includes support for both the HX834x LCD and the
    ADS7843E touchscreen controller on board the SAM3U-EK board.

    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 visiable 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 sam3u-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:

    1. 2013-6-28:  Created the configuration but have not yet done
       anything with it.

    2. 2013-6-29:  Various changes to get a clean build of this
       configuration. Still untested.

    3. 20113-6-30:  I cannot load this program using AtmelStudio6.1.
       The total size with DEBUG on is 138.9 KB.  I have verified
       that the first 128KB may have been written correctly, but then
       the code above 128KB wraps and overwrites the code at the
       beginning of FLASH, trashing the FLASH images.

       Bottom line:  Still untested.