README

This README file discusses the port of NuttX to the Olimex LPC-H3131 board.

NOTE: This is a minimal port to the Olimex LPC-H3131. According to Olimex documentation, the LPC-H3131 is similar in design to the Embedded Artists EA3131. As a consequence, it should be possible to leverage additional functionality from boards/arm/lpc31xx/ea3131 without too much difficulty.

Contents

o Development Environment o GNU Toolchain Options o IDEs o NuttX buildroot Toolchain o Boot Sequence o Buttons and LEDs o Image Format o Image Download to ISRAM o Using OpenOCD and GDB o ARM/LPC-H3131-specific Configuration Options o 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.

GNU Toolchain Options

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

1. The NuttX buildroot Toolchain (see below), or
2. Any generic arm-none-eabi GNU toolchain.

All testing has been conducted using the NuttX buildroot toolchain. To use a different toolchain, you simply need to modify the configuration. As an example:

CONFIG_ARM_TOOLCHAIN_GNU_EABI : Generic arm-none-eabi toolchain

Generic arm-none-eabi GNU Toolchain

There are a number of toolchain projects providing support for ARMv4/v5 class processors, including:

GCC ARM Embedded
  https://developer.arm.com/open-source/gnu-toolchain/gnu-rm

Others exist for various Linux distributions, MacPorts, etc. Any version based on GCC 4.6.3 or later should work.

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/lpc31xx, arch/arm/src/common, arch/arm/src/arm, 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/lpc31xx/lpc31_vectors.S. You may have to build NuttX one time from the Cygwin command line in order to obtain the pre-built startup object needed by an IDE.

NuttX buildroot Toolchain

A GNU GCC-based toolchain is assumed. The PATH environment variable 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 Bitbucket download site (https://bitbucket.org/nuttx/buildroot/downloads/). This GNU toolchain builds and executes in the Linux or Cygwin environment.

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

   tools/configure.sh olimex-lpc-h3131:<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 boards/arm926t-defconfig-4.2.4 .config

6. make oldconfig

7. make

8. Make sure that the PATH variable includes the path to the newly built binaries.

See the file boards/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.

Boot Sequence

LPC313x has on chip bootrom which loads properly formatted images from multiple sources into SRAM. These sources include including SPI Flash, NOR Flash, UART, USB, SD Card, and NAND Flash.

In all configurations, NuttX is loaded directly into ISRAM. NuttX is linked to execute from ISRAM, regardless of the boot source.

Buttons and LEDs

Buttons -------

There are no user buttons on the H3131

LEDs ----

There are two LEDs on the LPC-H3131 that can be controlled by software:

  LED              GPIO
  ---------------- -----
  LED1 Yellow      GPIO17 High output illuminates
  LED2 Green       GPIO18 High output illuminates

Both can be illuminated by driving the GPIO output to high.

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/lpc31_leds.c. The LEDs are used to encode OS-related events as follows:

SYMBOL                Meaning                     LED state
                                                LED2     LED1
-------------------  -----------------------  -------- --------
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            N/C      N/C
LED_SIGNAL           In a signal handler        N/C      N/C
LED_ASSERTION        An assertion failed        N/C      N/C
LED_PANIC            The system has crashed     N/C      Blinking
LED_IDLE             MCU is is sleep mode         Not used

Thus if LED2 is statically on, NuttX has successfully booted and is, apparently, running normmally. If LED1 is flashing at approximately 2Hz, then a fatal error has been detected and the system has halted.

NOTE: That LED2 is not used after completion of booting and may be used by other board-specific logic.

Image Format

In order to use the bootrom bootloader, a special header must be added to the beginning of the binary image that includes information about the binary (things like the entry point, the size, and CRC's to verify the image.

NXP provides a Windows program to append such a header to the binary image. However, (1) that program won't run under Linux, and (2) when I try it under WinXP, Symantec immediately claims that the program is misbehaving and deletes it!

To work around both of these issues, I have created a small program under boards/olimex-lpc-h3131/tools to add the header. This program can be built under either Linux or Cygwin (and probably other tool environments as well). That tool can be built as follows:

• cd boards/olimex-lpc-h3131/tools
• make

Then, to build the NuttX binary ready to load with the bootloader, just following these steps:

• tools/configure.sh olimex-lpc-h3131:ostest # (using the ostest configuration for this example)
• cd .. # Set up environment
• make # Make NuttX. This will produce nuttx.bin
• mklpc.sh # Make the bootloader binary (nuttx.lpc)

NOTES:

1. Make sure to set your PATH variable appropriately or use the full path
   to mklpc.sh in the final step.
2. You can instruct Symantec to ignore the errors and it will stop
   quarantining the NXP program.
3. The CRC32 logic in boards/olimex-lpc-h3131/tools doesn't seem to
   work.  As a result, the CRC is currently disabled in the header:

   RCS file: /cvsroot/nuttx/nuttx/boards/olimex-lpc-h3131/tools/lpchdr.c,v
   retrieving revision 1.2
   diff -r1.2 lpchdr.c
   264c264
   <   g_hdr.imagetype       = 0x0000000b;
   ---
   >   g_hdr.imagetype       = 0x0000000a;

Image Download to ISRAM

Assuming that you already have the FTDI driver installed*, then here is the are the steps that I use for loading new code into the LPC-H3131:

1. Create the bootloader binary, nuttx.lpc, as described above.

2. With the power off, set the boot jumpers to enable booting from UART. The boot jumpers are the block of three jumper just in-board from the JTAG connector; Jumper pair 1-2 is the pair furthest from the JTAG connector:

   1-2: Closed 3-4: Closed 5-6: Open

3. Connected the LPC-H3131 using the FTDI USB port (not the lpc3131 USB port) This will power up the LPC-H3131 and start the bootloader.

4. Start a terminal emulator (such as TeraTerm) at 115200 8NI.

5. Reset the LPC-H3131 and you should see:

   LPC31xx READY FOR PLAIN IMAGE>

6. Send the nuttx.lpc file and you should see:

   Download finished

That will load the NuttX binary into ISRAM and attempt to execute it.

*See the LPC313x documentation if you do not have the FTDI driver installed.

TeraTerm Note: This is how to send a file from TeraTerm. It is essentially step 6 exploded in more detail for the case of TeraTerm:

1. Start the ROM bootloader as described above.

2. At the "LPC31xx READY FOR PLAIN IMAGE>" prompt, open the File menu and select the "Send File..." option.

3. Select the file to send,

4. Before "Open" -ing the file MAKE SURE TO CHECK THE "Binary" BOX! This has cost me a few hours a few times because I forget to do this. The program will NOT RUN is sent non-binary.

   [NO, I am not SHOUTING. I am just making sure that I never forget to do this again].

5. "Open"-ing the file will send it to the ROM bootloader.

6. You should see "Download finished" from the bootloader followed immediately by any serial console output from your program.

Using OpenOCD and GDB

[NOTE: As of this writing, my OpenOCD script does NOT work. It fails because it is unable to halt the LPC3131. So, unfortunately, OpenOCD is not a option right now.]

I have been using the Olimex ARM-USB-OCD JTAG debugger with the LPC-H3131 (http://www.olimex.com). The OpenOCD configuration file is here: tools/armusbocb.cfg. There is also a script on the tools directory that I used to start the OpenOCD daemon on my system called oocd.sh. That script would probably require some modifications to work in another environment:

- possibly the value of OPENOCD_PATH
- If you are working under Linux you will need to change any
  occurrences of `cygpath -w blablabla` to just blablabla

Then you should be able to start the OpenOCD daemon like:

boards/olimex-lpc-h3131/tools/oocd.sh $PWD

Where it is assumed that you are executing oocd.sh from the top level directory where NuttX is installed.

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

And you can load the NuttX ELF file:

(gdb) symbol-file nuttx (gdb) load nuttx

ARM/LPC-H3131-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_ARM926EJS=y

CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory

   CONFIG_ARCH_CHIP=lpc313x

CONFIG_ARCH_CHIP_name - For use in C code

   CONFIG_ARCH_CHIP_LPC3131

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

   CONFIG_ARCH_BOARD="olimex-lpc-h3131"

CONFIG_ARCH_BOARD_name - For use in C code

   CONFIG_ARCH_BOARD_OLIMEX_LPC_H3131

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 - For most ARM9 architectures, this describes the
  size of installed DRAM.  For the LPC313X, it is used only to
  determine how to map the executable regions.  It is SDRAM size
  only if you are executing out of the external SDRAM; or it could
  be NOR FLASH size, external SRAM size, or internal SRAM size.

CONFIG_RAM_START - The start address of installed DRAM (physical)

CONFIG_RAM_VSTART - The startaddress of DRAM (virtual)

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_BUTTONS -  Enable support for buttons. Unique to board architecture.

CONFIG_ARCH_DMA - Support DMA initialization

CONFIG_ARCH_LOWVECTORS - define if vectors reside at address 0x0000:00000
  Undefine if vectors reside at address 0xffff:0000

CONFIG_ARCH_ROMPGTABLE - A pre-initialized, read-only page table is available.
  If defined, then board-specific logic must also define PGTABLE_BASE_PADDR,
  PGTABLE_BASE_VADDR, and all memory section mapping in a file named
  board_memorymap.h.

Individual subsystems can be enabled:

CONFIG_LPC31_MCI, CONFIG_LPC31_SPI, CONFIG_LPC31_UART

External memory available on the board (see also CONFIG_MM_REGIONS)

CONFIG_LPC31_EXTSRAM0 - Select if external SRAM0 is present
CONFIG_LPC31_EXTSRAM0HEAP - Select if external SRAM0 should be
  configured as part of the NuttX heap.
CONFIG_LPC31_EXTSRAM0SIZE - Size (in bytes) of the installed
  external SRAM0 memory
CONFIG_LPC31_EXTSRAM1 - Select if external SRAM1 is present
CONFIG_LPC31_EXTSRAM1HEAP - Select if external SRAM1 should be
  configured as part of the NuttX heap.
CONFIG_LPC31_EXTSRAM1SIZE - Size (in bytes) of the installed
  external SRAM1 memory
CONFIG_LPC31_EXTDRAM - Select if external SDRAM is present
CONFIG_LPC31_EXTDRAMHEAP - Select if external SDRAM should be
  configured as part of the NuttX heap.
CONFIG_LPC31_EXTDRAMSIZE - Size (in bytes) of the installed
  external SDRAM memory
CONFIG_LPC31_EXTNAND - Select if external NAND is present
CONFIG_LPC31_EXTNANDSIZE - Size (in bytes) of the installed
  external NAND memory

LPC313X specific device driver settings

CONFIG_UART_SERIAL_CONSOLE - selects the UART for the
  console and ttys0
CONFIG_UART_RXBUFSIZE - Characters are buffered as received.
  This specific the size of the receive buffer
CONFIG_UART_TXBUFSIZE - Characters are buffered before
  being sent.  This specific the size of the transmit buffer
CONFIG_UART_BAUD - The configure BAUD of the UART.  Must be
CONFIG_UART_BITS - The number of bits.  Must be either 7 or 8.
CONFIG_UART_PARTIY - 0=no parity, 1=odd parity, 2=even parity
CONFIG_UART_2STOP - Two stop bits

Configurations

Configurations

Information Common to All Configurations

Each LPC-H3131 configuration is maintained in a sub-directory and can be selected as follow:

tools/configure.sh olimex-lpc-h3131:<subdir>

Before building, make sure the PATH environment variable includes 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
   see additional README.txt files in the NuttX tools repository.

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

2. Unless stated otherwise, all configurations generate console output on the UART0 associated with the FT232RL USB-to UART converter.

3. Unless otherwise stated, the configurations are setup for Windows undery Cygwin. This can, however, be easily reconfigured.

4. 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_ARM_TOOLCHAIN_GNU_EABI=y : GNU EABI toolchain for windows

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

nsh: Configures the NuttShell (nsh) located at examples/nsh. The Configuration enables only the serial NSH interface.

General Configuration.  These are easily change by modifying the NuttX
configuration:

  - Console on UART -> UART-to-USB converter
  - Platform: Windows with Cygwin
  - Toolchain:  ARM EABI GCC for Windows

NOTES:
1. Built-in applications are not supported by default.  To enable NSH
   built-in applications:

   Binary
     CONFIG_BUILTIN=y                      : Support built-in applications

   Application Configuration -> NSH Library
     CONFIG_NSH_BUILTIN_APPS=y             : Enable built-in applications

2. SDRAM support is not enabled by default.  SDRAM support can be enabled
   by adding the following to your NuttX configuration file:

   [NOTE: There is still something wrong with the SDRAM setup.  At present
    it hangs on the first access from SDRAM during configuration.]

   System Type->LPC31xx Peripheral Support
     CONFIG_LPC31_EXTDRAM=y                : Enable external DRAM support
     CONFIG_LPC31_EXTDRAMSIZE=33554432     : 256Mbit -> 32Mbyte
     CONFIG_LPC31_SDRAM_16BIT=y            : Organized 16Mbit x 16 bits wide

   Now that you have SDRAM enabled, what are you going to do with it?  One
   thing you can is add it to the heap

   System Type->Heap Configuration
     CONFIG_LPC31_EXTDRAMHEAP=y            : Add the SDRAM to the heap

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

   Another thing you could do is to enable the RAM test built-in
   application:

3. You can enable the NuttX RAM test that may be used to verify the
   external SDAM.  To do this, keep the SDRAM out of the heap so that
   it can be tested without crashing programs using the memory.

   First enable built-in applications as described above, then make
   the following additional modifications to the NuttX configuration:

   System Type->Heap Configuration
     CONFIG_LPC31_EXTDRAMHEAP=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_TESTING_RAMTEST=y

   In this configuration, the SDRAM is not added to heap and so is not
   excessible 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: ramtest [-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 30000000 33554432
   RAMTest: Marching ones: 30000000 33554432
   RAMTest: Marching zeroes: 30000000 33554432
   RAMTest: Pattern test: 30000000 33554432 55555555 aaaaaaaa
   RAMTest: Pattern test: 30000000 33554432 66666666 99999999
   RAMTest: Pattern test: 30000000 33554432 33333333 cccccccc
   RAMTest: Address-in-address test: 30000000 33554432

4. This configuration has been used to test USB host functionality.  USB
   host is *not* enabled by default.  If you will to enable USB host
   support in the NSH configuration, please modify the NuttX
   configuration as follows:

   a) Basic USB Host support

      Drivers -> USB Host Driver Support
        CONFIG_USBHOST=y              : General USB host support
        CONFIG_USBHOST_INT_DISABLE=n  : Interrupt EPs need with hub, HID keyboard, and HID mouse
        CONFIG_USBHOST_ISOC_DISABLE=y : Not needed (or supported)

      System Type -> Peripherals
        CONFIG_LPC31_USBOTG=y         : Enable the USB OTG peripheral

      System Type -> USB host configuration
        CONFIG_LPC31_EHCI_BUFSIZE=128
        CONFIG_LPC31_EHCI_PREALLOCATE=y

      RTOS Features -> Work Queue Support
        CONFIG_SCHED_WORKQUEUE=y      : High priority queue support is needed
        CONFIG_SCHED_HPWORK=y
        CONFIG_SCHED_HPWORKSTACKSIZE=1536 (1024 seems to work okay too)

   b. Hub Support.

      Drivers -> USB Host Driver Support
        CONFIG_USBHOST_INT_DISABLE=n  : Interrupt endpoint support needed
        CONFIG_USBHOST_HUB=y          : Enable the hub class
        CONFIG_USBHOST_ASYNCH=y       : Asynchronous I/O supported needed for hubs

      RTOS Features -> Work Queue Support
        CONFIG_SCHED_LPWORK=y         : Low priority queue support is needed
        CONFIG_SCHED_LPNTHREADS=1
        CONFIG_SCHED_LPWORKSTACKSIZE=1024

      NOTES:

      1. It is necessary to perform work on the low-priority work queue
         (vs. the high priority work queue) because:

         a. Deferred work requires some delays and waiting, and
         b. There are dependencies between the waiting and driver
            interrupt related work.  Since that interrupt related work
            will performed on the high priority work queue, there would
            be the likelihood of deadlocks if you wait for events on the
            high priority work thread that can only occur if the high
            priority work thread is available to post those events.

      2. Logic nesting becomes deeper with a hub and it may also be
         necessary to increase some stack sizes.

   c. USB Mass Storage Class.  With this class enabled, you can support
      connection of USB FLASH storage drives.  Support for the USB
      mass storage class is enabled like this:

      Drivers -> USB Host Driver Support
        CONFIG_USBHOST_MSC=y          : Mass storage class support

      The MSC class will work like this.  When you first start NSH, you
      can look at the available devices like this:

        NuttShell (NSH) NuttX-6.31
        nsh> ls -l /dev
        /dev:
         crw-rw-rw-       0 console
         crw-rw-rw-       0 null
         crw-rw-rw-       0 ttyS0

      The crw-rw-rw- indicates a readable, write-able character device.

        nsh> ls -l /dev
        /dev:
         crw-rw-rw-       0 console
         crw-rw-rw-       0 null
         brw-rw-rw-       0 sda
         crw-rw-rw-       0 ttyS0

      The brw-rw-rw- indicates a readable, write-able block device.
      This block device can then be mounted like this:

        nsh> mount -t vfat /dev/sda /mnt/flash

      The USB FLASH drive contents are then visible under /mnt/flash and
      can be operated on with normal file system commands like:

        nsh> mount -t vfat /dev/sda /mnt/flash
        nsh> cat /mnt/flash/filec.c
        etc.

      It is recommended that the drive by unmounted BEFORE it is
      removed.  That is not always possible so if the USB FLASH is
      removed BEFORE the drive is unmounted, the device at /dev/sda will
      persist in an unusable stack until it is unmounted with the
      following command (NOTE:  If the FLASH drive is re-inserted in
      this state, it will appear as /dev/sdb):

        nsh> umount /mnt/flash

   d. HID Keyboard support.  The following support will enable support
      for certain keyboard devices (only the so-called "boot" keyboard
      class is supported):

      Drivers -> USB Host Driver Support
        CONFIG_USBHOST_HIDKBD=y       : HID keyboard class support

      Drivers -> USB Host Driver Support
        CONFIG_USBHOST_INT_DISABLE=n  : Interrupt endpoint support needed

      In this case, when the HID keyboard is installed, you see a new
      character device called /dev/kbda.

      There is a HID keyboard test example that can be enabled with the
      following settings.  NOTE:  In this case, NSH is disabled because
      the HID keyboard test is a standalone test.

      This selects the HIDKBD example:

      Application Configuration -> Examples
        CONFIG_EXAMPLES_HIDKBD=y
        CONFIG_EXAMPLES_HIDKBD_DEVNAME="/dev/kbda"

      RTOS Features
        CONFIG_INIT_ENTRYPOINT="hidkbd_main"

      These settings disable NSH:

      Application Configuration -> Examples
        CONFIG_SYSTEM_NSH=n

      Application Configuration -> NSH Library
        CONFIG_NSH_LIBRARY=y

      Using the HID Keyboard example:  Anything typed on the keyboard
      should be echoed on the serial console.  Here is some sample of
      a session:

      Initialization

        hidkbd_main: Register class drivers
        hidkbd_main: Initialize USB host keyboard driver
        hidkbd_main: Start hidkbd_waiter
        hidkbd_waiter: Running

      The test example will periodically attempt to open /dev/kbda

        Opening device /dev/kbda
        Failed: 2
        Opening device /dev/kbda
        Failed: 2
        etc.

      The open will fail each time because there is no keyboard
      attached.  When a USB keyboard is attached, the open of /dev/kbda
      will succeed and the test will begin echoing data to the serial
      console:

        hidkbd_waiter: connected
        Opening device /dev/kbda
        Device /dev/kbda opened

      For example, this text was entered from the keyboard:

        Now is the time for all good men to come to the aid of their party.

      Then when the device is removed, the test will resume attempting
      to open the driver until the next time it is connected

        Closing device /dev/kbda: -1
        Opening device /dev/kbda
        Failed: 19
        hidkbd_waiter: disconnected

        Opening device /dev/kbda
        Failed: 2
        etc.

   d. The USB monitor can also be enabled:

     Drivers -> USB Host Driver Support
       CONFIG_USBHOST_TRACE=y
       CONFIG_USBHOST_TRACE_NRECORDS=128
       CONFIG_USBHOST_TRACE_VERBOSE=y

     Application Configuration -> System Add-Ons
       CONFIG_USBMONITOR=y
       CONFIG_USBMONITOR_INTERVAL=1

   NOTE:  I have found that if you enable USB DEBUG and/or USB tracing,
   the resulting image requires to much memory to execute out of
   internal SRAM.  I was able to get the configurations to run out of
   SRAM with debug/tracing enabled by carefully going through the
   configuration and reducing stack sizes, disabling unused OS features,
   disabling un-necessary NSH commands, etc.

5. Making the Configuration Smaller.  This configuration runs out of
   internal SRAM.  If you enable many features, then your code image
   may outgrow the available SRAM; even if the code can be loaded into
   SRAM, it may still fail at runtime due to insufficient memory.

   Since SDRAM is not currently working (see above) and NAND support
   has not be integrated, the only really option is to put NSH "on a
   diet" to reduct the size so that it will fit into memory.

   Here are a few things you can do:

   1. Try using smaller stack sizes,

   2. Disable operating system features.  Here some that can go:

      CONFIG_DISABLE_ENVIRON=y
      CONFIG_DISABLE_MQUEUE=y
      CONFIG_DISABLE_POSIX_TIMERS=y
      CONFIG_DISABLE_PTHREAD=y
      CONFIG_MQ_MAXMSGSIZE=0
      CONFIG_NUNGET_CHARS=0
      CONFIG_PREALLOC_MQ_MSGS=0

   3. Disable NSH commands.  I can life fine without these:

      CONFIG_NSH_DISABLE_ADDROUTE=y
      CONFIG_NSH_DISABLE_CD=y
      CONFIG_NSH_DISABLE_CMP=y
      CONFIG_NSH_DISABLE_CP=y
      CONFIG_NSH_DISABLE_DELROUTE=y
      CONFIG_NSH_DISABLE_EXEC=y
      CONFIG_NSH_DISABLE_EXIT=y
      CONFIG_NSH_DISABLE_GET=y
      CONFIG_NSH_DISABLE_HEXDUMP=y
      CONFIG_NSH_DISABLE_IFCONFIG=y
      CONFIG_NSH_DISABLE_LOSETUP=y
      CONFIG_NSH_DISABLE_MB=y
      CONFIG_NSH_DISABLE_MH=y
      CONFIG_NSH_DISABLE_MKFIFO=y
      CONFIG_NSH_DISABLE_MKRD=y
      CONFIG_NSH_DISABLE_NFSMOUNT=y
      CONFIG_NSH_DISABLE_PING=y
      CONFIG_NSH_DISABLE_PUT=y
      CONFIG_NSH_DISABLE_PWD=y
      CONFIG_NSH_DISABLE_RM=y
      CONFIG_NSH_DISABLE_RMDIR=y
      CONFIG_NSH_DISABLE_SET=y
      CONFIG_NSH_DISABLE_SOURCE=y
      CONFIG_NSH_DISABLE_SLEEP=y
      CONFIG_NSH_DISABLE_TEST=y
      CONFIG_NSH_DISABLE_UNSET=y
      CONFIG_NSH_DISABLE_USLEEP=y
      CONFIG_NSH_DISABLE_WGET=y
      CONFIG_NSH_DISABLE_XD=y