README
======

This README discusses issues unique to NuttX configurations for the
STMicro STM32F3Discovery development board.

Contents
========

  - Development Environment
  - GNU Toolchain Options
  - IDEs
  - NuttX EABI "buildroot" Toolchain
  - NuttX OABI "buildroot" Toolchain
  - NXFLAT Toolchain
  - LEDs
  - Serial Console
  - FPU
  - Debugging
  - STM32F3Discovery-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.

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

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

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

  All testing has been conducted using the CodeSourcery toolchain for Windows.  To use
  the Atollic, devkitARM, Raisonance GNU, or NuttX buildroot 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        : The Atollic toolchain under Windows
    CONFIG_ARMV7M_TOOLCHAIN_DEVKITARM=y      : devkitARM under Windows
    CONFIG_ARMV7M_TOOLCHAIN_RAISONANCE=y     : Raisonance RIDE7 under Windows
    CONFIG_ARMV7M_TOOLCHAIN_BUILDROOT=y      : NuttX buildroot under Linux or Cygwin (default)

  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 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 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

  The CodeSourcery Toolchain (2009q1)
  -----------------------------------
  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.

  The Atollic "Pro" and "Lite" Toolchain
  --------------------------------------
  One problem that I had with the Atollic toolchains is that the provide a gcc.exe
  and g++.exe in the same bin/ file as their ARM binaries.  If the Atollic bin/ path
  appears in your PATH variable before /usr/bin, then you will get the wrong gcc
  when you try to build host executables.  This will cause to strange, uninterpretable
  errors build some host binaries in tools/ when you first make.

  Also, the Atollic toolchains are the only toolchains that have built-in support for
  the FPU in these configurations.  If you plan to use the Cortex-M4 FPU, you will
  need to use the Atollic toolchain for now.  See the FPU section below for more
  information.

  The Atollic "Lite" Toolchain
  ----------------------------
  The free, "Lite" version of the Atollic toolchain does not support C++ nor
  does it support ar, nm, objdump, or objdcopy. If you use the Atollic "Lite"
  toolchain, you will have to set:

    CONFIG_HAVE_CXX=n

  In order to compile successfully.  Otherwise, you will get errors like:

    "C++ Compiler only available in TrueSTUDIO Professional"

  The make may then fail in some of the post link processing because of some of
  the other missing tools.  The Make.defs file replaces the ar and nm with
  the default system x86 tool versions and these seem to work okay.  Disable all
  of the following to avoid using objcopy:

    CONFIG_RRLOAD_BINARY=n
    CONFIG_INTELHEX_BINARY=n
    CONFIG_MOTOROLA_SREC=n
    CONFIG_RAW_BINARY=n

  devkitARM
  ---------
  The devkitARM toolchain includes a version of MSYS make.  Make sure that the
  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/stm32,
     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/stm32/stm32_vectors.S.  With RIDE, I have to build NuttX
  one time from the Cygwin command line in order to obtain the pre-built
  startup object needed by RIDE.

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

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

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

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

     cd tools
     ./configure.sh STM32F3Discovery/<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 lpcxpresso-lpc1768/<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 STM32F3Discovery board has ten LEDs.  Two of these are controlled by
logic on the board and are not available for software control:

LD1 PWR:   red LED indicates that the board is powered.
LD2 COM:   LD2 default status is red. LD2 turns to green to indicate that
           communications are in progress between the PC and the ST-LINK/V2.

And eight can be controlled by software:

User LD3:  red LED is a user LED connected to the I/O PE9 of the
           STM32F303VCT6.
User LD4:  blue LED is a user LED connected to the I/O PE8 of the
           STM32F303VCT6.
User LD5:  orange LED is a user LED connected to the I/O PE10 of the
           STM32F303VCT6.
User LD6:  green LED is a user LED connected to the I/O PE15 of the
           STM32F303VCT6.
User LD7:  green LED is a user LED connected to the I/O PE11 of the
           STM32F303VCT6.
User LD8:  orange LED is a user LED connected to the I/O PE14 of the
           STM32F303VCT6.
User LD9:  blue LED is a user LED connected to the I/O PE12 of the
           STM32F303VCT6.
User LD10: red LED is a user LED connected to the I/O PE13 of the
           STM32F303VCT6.

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

  SYMBOL                Meaning                 LED state
                                                Initially all LEDs are OFF
  -------------------  -----------------------  ------------- ------------
  LED_STARTED          NuttX has been started   LD3 ON
  LED_HEAPALLOCATE     Heap has been allocated  LD4 ON
  LED_IRQSENABLED      Interrupts enabled       LD4 ON
  LED_STACKCREATED     Idle stack created       LD6 ON
  LED_INIRQ            In an interrupt          LD7 should glow
  LED_SIGNAL           In a signal handler      LD8 might glow
  LED_ASSERTION        An assertion failed      LD9 ON while handling the assertion
  LED_PANIC            The system has crashed   LD10 Blinking at 2Hz
  LED_IDLE             STM32 is is sleep mode   (Optional, not used)

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

The STM32F3Discovery has no on-board RS-232 driver, however USART2 is
configuration as the serial console in all configurations that use a serial
console.

There are many options for USART2 RX and TX pins.  They configured to use
PA2 (TX) and PA3 (RX) for connection to an external serial device because of
the following settings in the include/board.h file:

  #define GPIO_USART2_RX GPIO_USART2_RX_2
  #define GPIO_USART2_TX GPIO_USART2_TX_2

This can be found on the board at:

  TX, PA2, Connector P1, pin 14
  RX, PA3, Connector P1, pin 11

FPU
===

FPU Configuration Options
-------------------------

There are two version of the FPU support built into the STM32 port.

1. Lazy Floating Point Register Save.

   This is an untested implementation that saves and restores FPU registers
   only on context switches.  This means: (1) floating point registers are
   not stored on each context switch and, hence, possibly better interrupt
   performance.  But, (2) since floating point registers are not saved,
   you cannot use floating point operations within interrupt handlers.

   This logic can be enabled by simply adding the following to your .config
   file:

   CONFIG_ARCH_FPU=y

2. Non-Lazy Floating Point Register Save

   Mike Smith has contributed an extensive re-write of the ARMv7-M exception
   handling logic. This includes verified support for the FPU.  These changes
   have not yet been incorporated into the mainline and are still considered
   experimental.  These FPU logic can be enabled with:

   CONFIG_ARCH_FPU=y
   CONFIG_ARMV7M_CMNVECTOR=y

   You will probably also changes to the ld.script in if this option is selected.
   This should work:

   -ENTRY(_stext)
   +ENTRY(__start)         /* Treat __start as the anchor for dead code stripping */
   +EXTERN(_vectors)       /* Force the vectors to be included in the output */

CFLAGS
------

Only recent GCC toolchains have built-in support for the Cortex-M4 FPU.  You will see
the following lines in each Make.defs file:

  ifeq ($(CONFIG_ARCH_FPU),y)
    ARCHCPUFLAGS = -mcpu=cortex-m4 -mthumb -march=armv7e-m -mfpu=fpv4-sp-d16 -mfloat-abi=hard
  else
    ARCHCPUFLAGS = -mcpu=cortex-m3 -mthumb -mfloat-abi=soft
  endif

Configuration Changes
---------------------

Below are all of the configuration changes that I had to make to configs/stm3240g-eval/nsh2
in order to successfully build NuttX using the Atollic toolchain WITH FPU support:

  -CONFIG_ARCH_FPU=n                       : Enable FPU support
  +CONFIG_ARCH_FPU=y

  -CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYW=y : Disable the CodeSourcery toolchain
  +CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYW=n

  -CONFIG_ARMV7M_TOOLCHAIN_ATOLLIC=n       : Enable the Atollic toolchain
  +CONFIG_ARMV7M_TOOLCHAIN_ATOLLIC=y       :

  -CONFIG_INTELHEX_BINARY=y                : Suppress generation FLASH download formats
  +CONFIG_INTELHEX_BINARY=n                : (Only necessary with the "Lite" version)

  -CONFIG_HAVE_CXX=y                       : Suppress generation of C++ code
  +CONFIG_HAVE_CXX=n                       : (Only necessary with the "Lite" version)

See the section above on Toolchains, NOTE 2, for explanations for some of
the configuration settings.  Some of the usual settings are just not supported
by the "Lite" version of the Atollic toolchain.

Debugging
=========

STM32 ST-LINK Utility
---------------------
For simply writing to FLASH, I use the STM32 ST-LINK Utility.  At least
version 2.4.0 is required (older versions do not recognize the STM32 F3
device).  This utility is available from free from the STMicro website.

Debugging
---------
If you are going to use a debugger, you should make sure that the following
settings are selection in your configuration file:

  CONFIG_DEBUG_SYMBOLS=y     : Enable debug symbols in the build
  CONFIG_ARMV7M_USEBASEPRI=y : Use the BASEPRI register to disable interrupts

OpenOCD
-------
I am told that OpenOCD will work with the ST-Link, but I have never tried
it.

https://github.com/texane/stlink
--------------------------------
This is an open source server for the ST-Link that I have never used.

Atollic GDB Server
------------------
You can use the Atollic IDE, but I have never done that either.

STM32F3Discovery-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_CORTEXM4=y

    CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory

       CONFIG_ARCH_CHIP=stm32

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

       CONFIG_ARCH_CHIP_STM32F303VC=y

    CONFIG_ARCH_BOARD_STM32_CUSTOM_CLOCKCONFIG - Enables special STM32 clock
       configuration features.

       CONFIG_ARCH_BOARD_STM32_CUSTOM_CLOCKCONFIG=n

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

       CONFIG_ARCH_BOARD=STM32F3Discovery (for the STM32F3Discovery development board)

    CONFIG_ARCH_BOARD_name - For use in C code

       CONFIG_ARCH_BOARD_STM32F3_DISCOVERY=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=0x00010000 (64Kb)

    CONFIG_RAM_START - The start address of installed DRAM

       CONFIG_RAM_START=0x20000000

    CONFIG_STM32_CCMEXCLUDE - Exclude CCM SRAM from the HEAP

    CONFIG_ARCH_FPU - The STM32F3Discovery supports a floating point unit (FPU)

       CONFIG_ARCH_FPU=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:

    AHB1
    ----
    CONFIG_STM32_DMA1
    CONFIG_STM32_DMA2
    CONFIG_STM32_CRC
    CONFIG_STM32_TSC

    AHB2
    ----
    (GPIOs are always enabled)

    AHB3
    ----
    CONFIG_STM32_ADC1
    CONFIG_STM32_ADC2
    CONFIG_STM32_ADC3
    CONFIG_STM32_ADC4

    APB1
    ----
    CONFIG_STM32_TIM2
    CONFIG_STM32_TIM3
    CONFIG_STM32_TIM4
    CONFIG_STM32_TIM6
    CONFIG_STM32_TIM7
    CONFIG_STM32_WWDG
    CONFIG_STM32_IWDG
    CONFIG_STM32_SPI2
    CONFIG_STM32_SPI3
    CONFIG_STM32_USART2
    CONFIG_STM32_USART3
    CONFIG_STM32_UART4
    CONFIG_STM32_UART5
    CONFIG_STM32_I2C1
    CONFIG_STM32_I2C2
    CONFIG_STM32_USB
    CONFIG_STM32_CAN1
    CONFIG_STM32_PWR -- Required for RTC
    CONFIG_STM32_DAC1

    APB2
    ----
    CONFIG_STM32_SYSCFG
    CONFIG_STM32_TIM1
    CONFIG_STM32_SPI1
    CONFIG_STM32_TIM8
    CONFIG_STM32_USART1
    CONFIG_STM32_TIM15
    CONFIG_STM32_TIM16
    CONFIG_STM32_TIM17

  Timer devices may be used for different purposes.  One special purpose is
  to generate modulated outputs for such things as motor control.  If CONFIG_STM32_TIMn
  is defined (as above) then the following may also be defined to indicate that
  the timer is intended to be used for pulsed output modulation, ADC conversion,
  or DAC conversion. Note that ADC/DAC require two definition:  Not only do you have
  to assign the timer (n) for used by the ADC or DAC, but then you also have to
  configure which ADC or DAC (m) it is assigned to.

    CONFIG_STM32_TIMn_PWM   Reserve timer n for use by PWM, n=1,..,14
    CONFIG_STM32_TIMn_ADC   Reserve timer n for use by ADC, n=1,..,14
    CONFIG_STM32_TIMn_ADCm  Reserve timer n to trigger ADCm, n=1,..,14, m=1,..,3
    CONFIG_STM32_TIMn_DAC   Reserve timer n for use by DAC, n=1,..,14
    CONFIG_STM32_TIMn_DACm  Reserve timer n to trigger DACm, n=1,..,14, m=1,..,2

  For each timer that is enabled for PWM usage, we need the following additional
  configuration settings:

    CONFIG_STM32_TIMx_CHANNEL - Specifies the timer output channel {1,..,4}

  NOTE: The STM32 timers are each capable of generating different signals on
  each of the four channels with different duty cycles.  That capability is
  not supported by this driver:  Only one output channel per timer.

  JTAG Enable settings (by default only SW-DP is enabled):

    CONFIG_STM32_JTAG_FULL_ENABLE - Enables full SWJ (JTAG-DP + SW-DP)
    CONFIG_STM32_JTAG_NOJNTRST_ENABLE - Enables full SWJ (JTAG-DP + SW-DP)
      but without JNTRST.
    CONFIG_STM32_JTAG_SW_ENABLE - Set JTAG-DP disabled and SW-DP enabled

  STM32F3Discovery specific device driver settings

    CONFIG_U[S]ARTn_SERIAL_CONSOLE - selects the USARTn (n=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

  STM32F3Discovery CAN Configuration

    CONFIG_CAN - Enables CAN support (one or both of CONFIG_STM32_CAN1 or
      CONFIG_STM32_CAN2 must also be defined)
    CONFIG_CAN_EXTID - Enables support for the 29-bit extended ID.  Default
      Standard 11-bit IDs.
    CONFIG_CAN_FIFOSIZE - The size of the circular buffer of CAN messages.
      Default: 8
    CONFIG_CAN_NPENDINGRTR - The size of the list of pending RTR requests.
      Default: 4
    CONFIG_CAN_LOOPBACK - A CAN driver may or may not support a loopback
      mode for testing. The STM32 CAN driver does support loopback mode.
    CONFIG_CAN1_BAUD - CAN1 BAUD rate.  Required if CONFIG_STM32_CAN1 is defined.
    CONFIG_CAN2_BAUD - CAN1 BAUD rate.  Required if CONFIG_STM32_CAN2 is defined.
    CONFIG_CAN_TSEG1 - The number of CAN time quanta in segment 1. Default: 6
    CONFIG_CAN_TSEG2 - the number of CAN time quanta in segment 2. Default: 7
    CONFIG_CAN_REGDEBUG - If CONFIG_DEBUG is set, this will generate an
      dump of all CAN registers.

  STM32F3Discovery SPI Configuration

    CONFIG_STM32_SPI_INTERRUPTS - Select to enable interrupt driven SPI
      support. Non-interrupt-driven, poll-waiting is recommended if the
      interrupt rate would be to high in the interrupt driven case.
    CONFIG_STM32_SPI_DMA - Use DMA to improve SPI transfer performance.
      Cannot be used with CONFIG_STM32_SPI_INTERRUPT.

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

Each STM32F3Discovery configuration is maintained in a sub-directory and
can be selected as follow:

    cd tools
    ./configure.sh STM32F3Discovery/<subdir>
    cd -
    . ./setenv.sh

If this is a Windows native build, then configure.bat should be used
instead of configure.sh:

    configure.bat STM32F3Discovery\<subdir>

Where <subdir> is one of the following:

  nsh:
  ---
    Configures the NuttShell (nsh) located at apps/examples/nsh.  The
    Configuration enables the serial interfaces on USART2.  Support for
    builtin applications is enabled, but in the base configuration no
    builtin applications are selected (see NOTES below).

    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_WINDOWS=y                   : Builds under Windows
       CONFIG_WINDOWS_CYGWIN=y                 : Using Cygwin
       CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYW=y : CodeSourcery for Windows

    3. This configuration includes USB Support (CDC/ACM device)

       CONFIG_STM32_USB=y            : STM32 USB device support
       CONFIG_USBDEV=y               : USB device support must be enabled
       CONFIG_CDCACM=y               : The CDC/ACM driver must be built
       CONFIG_NSH_BUILTIN_APPS=y     : NSH built-in application support must be enabled
       CONFIG_NSH_ARCHINIT=y         : To perform USB initialization

       The CDC/ACM example is included as two NSH "built-in" commands.\

       CONFIG_SYSTEM_CDCACM=y      : Enable apps/system/cdcacm

       The two commands are:

       sercon : Connect the serial device a create /dev/ttyACM0
       serdis : Disconnect the serial device.

       NOTE:  The serial connections/disconnections do not work as advertised.
       This is because the STM32F3Discovery board does not provide circuitry for
       control of the "soft connect" USB pullup.  As a result, the host PC
       does not know the USB has been logically connected or disconnected.  You
       have to follow these steps to use USB:

       1) Start NSH with USB disconnected
       2) enter to 'sercon' command to start the CDC/ACM device, then
       3) Connect the USB device to the host.

       and to close the connection:

       4) Disconnect the USB device from the host
       5) Enter the 'serdis' command

    4. This example can support the watchdog timer test (apps/examples/watchdog)
       but this must be enabled by selecting:

       CONFIG_EXAMPLES_WATCHDOG=y : Enable the apps/examples/watchdog
       CONFIG_WATCHDOG=y          : Enables watchdog timer driver support
       CONFIG_STM32_WWDG=y        : Enables the WWDG timer facility, OR
       CONFIG_STM32_IWDG=y        : Enables the IWDG timer facility (but not both)

       The WWDG watchdog is driven off the (fast) 42MHz PCLK1 and, as result,
       has a maximum timeout value of 49 milliseconds.  for WWDG watchdog, you
       should also add the fillowing to the configuration file:

       CONFIG_EXAMPLES_WATCHDOG_PINGDELAY=20
       CONFIG_EXAMPLES_WATCHDOG_TIMEOUT=49

       The IWDG timer has a range of about 35 seconds and should not be an issue.

  usbnsh:
  -------

    This is another NSH example.  If differs from other 'nsh' configurations
    in that this configurations uses a USB serial device for console I/O.
    Such a configuration is useful on the stm32f3discovery which has no
    builtin RS-232 drivers.

    Status:  As of this writing, this configuration has not ran properly.
    There appears to be some kind of driver-related issue.

    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.

       Build Setup:
         CONFIG_HOST_WINDOWS=y                   : Builds under Windows
         CONFIG_WINDOWS_CYGWIN=y                 : Using Cygwin

       System Type:
         CONFIG_ARMV7M_TOOLCHAIN_CODESOURCERYW=y : CodeSourcery for Windows

    3. This configuration does have USART2 output enabled and set up as
       the system logging device:

       Device Drivers -> System Logging Device Options:
         CONFIG_SYSLOG=y                    : Enable output to syslog, not console
         CONFIG_SYSLOG_CHAR=y               : Use a character device for system logging
         CONFIG_SYSLOG_DEVPATH="/dev/ttyS0" : USART2 will be /dev/ttyS0

       However, there is nothing to generate SYLOG output in the default
       configuration so nothing should appear on USART2 unless you enable
       some debug output or enable the USB monitor.

       NOTE:  Using the SYSLOG to get debug output has limitations.  Among
       those are that you cannot get debug output from interrupt handlers.
       So, in particularly, debug output is not a useful way to debug the
       USB device controller driver.  Instead, use the USB monitor with
       USB debug off and USB trance on (see below).

    4. Enabling USB monitor SYSLOG output.  If tracing is enabled, the USB
       device will save encoded trace output in in-memory buffer; if the
       USB monitor is enabled, that trace buffer will be periodically
       emptied and dumped to the system loggin device (USART2 in this
       configuraion):

        Device Drivers -> "USB Device Driver Support:
          CONFIG_USBDEV_TRACE=y                   : Enable USB trace feature
          CONFIG_USBDEV_TRACE_NRECORDS=256        : Buffer 128 records in memory

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

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

       NOTE: USB debug output also be enabled in this case.  Both will appear
       on the serial SYSLOG output.  However, the debug output will be
       asynchronous with the trace output and, hence, difficult to interpret.

    5. The STM32F3Discovery board does not provide circuitry for control of
       the "soft connect" USB pullup.  As a result, the host PC does not know
       the USB has been logically connected or disconnected.  You have to
       follow these steps to use USB:

       1) Start NSH with USB disconnected, then
       2) Connect the USB device to the host.

    6. Using the Prolifics PL2303 Emulation

       You could also use the non-standard PL2303 serial device instead of
       the standard CDC/ACM serial device by changing:

       Drivers->USB Device Driver Support
         CONFIG_CDCACM=n               : Disable the CDC/ACM serial device class
         CONFIG_CDCACM_CONSOLE=n       : The CDC/ACM serial device is NOT the console
         CONFIG_PL2303=y               : The Prolifics PL2303 emulation is enabled
         CONFIG_PL2303_CONSOLE=y       : The PL2303 serial device is the console
