px4-firmware/nuttx/configs/stm32f4discovery

README
======

This README discusses issues unique to NuttX configurations for the
STMicro STM32F4 Discovery development board.

Contents
========

  - Development Environment
  - GNU Toolchain Options
  - IDEs
  - NuttX buildroot Toolchain
  - LEDs
  - PWM
  - UARTs
  - Timer Inputs/Outputs
  - FPU
  - FSMC SRAM
  - STM32F4Discovery-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 because the Raisonance R-Link emulatator and some RIDE7 development tools
  were used and those tools works only under Windows.

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_STM32_CODESOURCERYW=y  : CodeSourcery under Windows
    CONFIG_STM32_CODESOURCERYL=y  : CodeSourcery under Linux
    CONFIG_STM32_ATOLLIC_LITE=y   : The free, "Lite" version of Atollic toolchain under Windows
    CONFIG_STM32_ATOLLIC_PRO=y    : The paid, "Pro" version of Atollic toolchain under Windows
    CONFIG_STM32_DEVKITARM=y      : devkitARM under Windows
    CONFIG_STM32_RAISONANCE=y     : Raisonance RIDE7 under Windows
    CONFIG_STM32_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.

     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

  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 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 STM32F4Discovery/<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 STM32F4Discovery board has four LEDs; green, organge, red and blue on the
board.. 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					LED1*	LED2	LED3	LED4
                                                green   orange  red     blue
	-------------------	-----------------------	-------	-------	-------	------
	LED_STARTED			NuttX has been started	ON		OFF		OFF		OFF
	LED_HEAPALLOCATE	Heap has been allocated	OFF		ON		OFF		OFF
	LED_IRQSENABLED		Interrupts enabled		ON		ON		OFF		OFF
	LED_STACKCREATED	Idle stack created		OFF		OFF		ON		OFF
	LED_INIRQ			In an interrupt**		ON		N/C		N/C		OFF
	LED_SIGNAL			In a signal handler***  N/C		ON		N/C		OFF
	LED_ASSERTION		An assertion failed		ON		ON		N/C		OFF
	LED_PANIC			The system has crashed	N/C		N/C		N/C		ON
    LED_IDLE            STM32 is is sleep mode  (Optional, not used)

  * If LED1, LED2, LED3 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 LED3 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.

PWM
===

The STM32F4Discovery has no real on-board PWM devices, but the board can be
configured to output a pulse train using TIM4 CH2 on PD3.  This pin is
available next to the audio jack.

UART
====

UART/USART PINS
---------------

USART1
  CK      PA8
  CTS     PA11*
  RTS     PA12*
  RX      PA10*, PB7
  TX      PA9*, PB6*
USART2
  CK      PA4*, PD7
  CTS     PA0*, PD3
  RTS     PA1, PD4*
  RX      PA3, PD6
  TX      PA2, PD5*
USART3
  CK      PB12, PC12*, PD10
  CTS     PB13, PD11
  RTS     PB14, PD12*
  RX      PB11, PC11, PD9
  TX      PB10*, PC10*, PD8
UART4
  RX      PA1, PC11
  TX      PA0*, PC10*
UART5
  RX      PD2
  TX      PC12*
USART6
  CK      PC8, PG7**
  CTS     PG13**, PG15**
  RTS     PG12**, PG8**
  RX      PC7*, PG9**
  TX      PC6, PG14**

 * Indicates pins that have other on-board functions and should be used only
   with care (See table 5 in the STM32F4Discovery User Guide).  The rest are
   free I/O pins.
** Port G pins are not supported by the MCU
 
Default USART/UART Configuration
--------------------------------
 
USART2 is enabled in all configurations (see */defconfig).  RX and TX are
configured on pins PA3 and PA2, respectively (see include/board.h).

Timer Inputs/Outputs
====================

TIM1
  CH1     PA8, PE9
  CH2     PA9*, PE11
  CH3     PA10*, PE13
  CH4     PA11*, PE14
TIM2
  CH1     PA0*, PA15, PA5*
  CH2     PA1, PB3*
  CH3     PA2, PB10*
  CH4     PA3, PB11
TIM3
  CH1     PA6*, PB4, PC6
  CH2     PA7*, PB5, PC7*
  CH3     PB0, PC8
  CH4     PB1, PC9
TIM4
  CH1     PB6*, PD12*
  CH2     PB7, PD13*
  CH3     PB8, PD14*
  CH4     PB9*, PD15*
TIM5
  CH1     PA0*, PH10**
  CH2     PA1, PH11**
  CH3     PA2, PH12**
  CH4     PA3, PI0
TIM8
  CH1     PC6, PI5
  CH2     PC7*, PI6
  CH3     PC8, PI7
  CH4     PC9, PI2
TIM9
  CH1     PA2, PE5
  CH2     PA3, PE6
TIM10
  CH1     PB8, PF6
TIM11
  CH1     PB9*, PF7
TIM12
  CH1     PH6**, PB14
  CH2     PC15, PH9**
TIM13
  CH1     PA6*, PF8
TIM14
  CH1     PA7*, PF9

 * Indicates pins that have other on-board functions and should be used only
   with care (See table 5 in the STM32F4Discovery User Guide).  The rest are
   free I/O pins.
** Port H pins are not supported by the MCU

Quadrature Encode Timer Inputs
------------------------------

If enabled (by setting CONFIG_QENCODER=y), then quadrature encoder will
use either TIM2 or TIM8 (see nsh/defconfig).  If TIM2 is selected, the input 
pins PA15 and PA1 for CH1 and CH2, respectively).  If TIM8 is selected, then
PC6 and PI5 will be used for CH1 and CH2  (see include board.h for pin
definitions).

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 the Atollic toolchain has built-in support for the Cortex-M4 FPU.  You will see
the following lines in each Make.defs file:

  ifeq ($(CONFIG_STM32_ATOLLIC_LITE),y)
    # Atollic toolchain under Windows
    ...
  ifeq ($(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
  endif

If you are using a toolchain other than the Atollic toolchain, then to use the FPU
you will also have to modify the CFLAGS to enable compiler support for the ARMv7-M
FPU.  As of this writing, there are not many GCC toolchains that will support the
ARMv7-M FPU.  

As a minimum you will need to add CFLAG options to (1) enable hardware floating point
code generation, and to (2) select the FPU implementation.  You might try the same
options as used with the Atollic toolchain in the Make.defs file:

  ARCHCPUFLAGS = -mcpu=cortex-m4 -mthumb -march=armv7e-m -mfpu=fpv4-sp-d16 -mfloat-abi=hard

FSMC SRAM
=========

On-board SRAM
-------------
The STM32F4Discovery has no on-board SRAM.  The information here is only for
reference in case you choose to add some.

Configuration Options
---------------------
Internal SRAM is available in all members of the STM32 family. The F4 family
also contains internal CCM SRAM.  This SRAM is different because it cannot
be used for DMA.  So if DMA needed, then the following should be defined
to exclude CCM SRAM from the heap:

  CONFIG_STM32_CCMEXCLUDE    : Exclude CCM SRAM from the HEAP

In addition to internal SRAM, SRAM may also be available through the FSMC.
In order to use FSMC SRAM, the following additional things need to be
present in the NuttX configuration file:

  CONFIG_STM32_FSMC=y        : Enables the FSMC
  CONFIG_STM32_FSMC_SRAM=y   : Indicates that SRAM is available via the
    FSMC (as opposed to an LCD or FLASH).
  CONFIG_HEAP2_BASE          : The base address of the SRAM in the FSMC
    address space
  CONFIG_HEAP2_END           : The end (+1) of the SRAM in the FSMC
    address space
  CONFIG_MM_REGIONS          : Must be set to a large enough value to
    include the FSMC SRAM 

SRAM Configurations
-------------------
There are 4 possible SRAM configurations:

  Configuration 1. System SRAM (only)
                   CONFIG_MM_REGIONS == 1
                   CONFIG_STM32_FSMC_SRAM NOT defined
                   CONFIG_STM32_CCMEXCLUDE defined
  Configuration 2. System SRAM and CCM SRAM
                   CONFIG_MM_REGIONS == 2
                   CONFIG_STM32_FSMC_SRAM NOT defined
                   CONFIG_STM32_CCMEXCLUDE NOT defined
  Configuration 3. System SRAM and FSMC SRAM
                   CONFIG_MM_REGIONS == 2
                   CONFIG_STM32_FSMC_SRAM defined
                   CONFIG_STM32_CCMEXCLUDE defined
  Configuration 4. System SRAM, CCM SRAM, and FSMC SRAM
                   CONFIG_MM_REGIONS == 3
                   CONFIG_STM32_FSMC_SRAM defined
                   CONFIG_STM32_CCMEXCLUDE NOT defined

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_STM32_CODESOURCERYW=y   : Disable the CodeSourcery toolchain
  +CONFIG_STM32_CODESOURCERYW=n

  -CONFIG_STM32_ATOLLIC_LITE=n   : Enable *one* the Atollic toolchains
   CONFIG_STM32_ATOLLIC_PRO=n
  -CONFIG_STM32_ATOLLIC_LITE=y   : The "Lite" version
   CONFIG_STM32_ATOLLIC_PRO=n    : The "Pro" version

  -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.

STM32F4Discovery-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_STM32F407IG=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=STM32F4Discovery (for the STM32F4Discovery development board)

    CONFIG_ARCH_BOARD_name - For use in C code

       CONFIG_ARCH_BOARD_STM32F4_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_DRAM_SIZE - Describes the installed DRAM (SRAM in this case):

       CONFIG_DRAM_SIZE=0x00010000 (64Kb)

    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_STM32_CCMEXCLUDE - Exclude CCM SRAM from the HEAP

    In addition to internal SRAM, SRAM may also be available through the FSMC.
    In order to use FSMC SRAM, the following additional things need to be
    present in the NuttX configuration file:

    CONFIG_STM32_FSMC_SRAM - Indicates that SRAM is available via the
      FSMC (as opposed to an LCD or FLASH).

    CONFIG_HEAP2_BASE - The base address of the SRAM in the FSMC address space

    CONFIG_HEAP2_END - The end (+1) of the SRAM in the FSMC address space

    CONFIG_ARCH_IRQPRIO - The STM3240xxx supports interrupt prioritization

       CONFIG_ARCH_IRQPRIO=y

    CONFIG_ARCH_FPU - The STM3240xxx 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_CRC
    CONFIG_STM32_BKPSRAM
    CONFIG_STM32_CCMDATARAM
    CONFIG_STM32_DMA1
    CONFIG_STM32_DMA2
    CONFIG_STM32_ETHMAC
    CONFIG_STM32_OTGHS

    AHB2
    ----
    CONFIG_STM32_DCMI
    CONFIG_STM32_CRYP
    CONFIG_STM32_HASH
    CONFIG_STM32_RNG
    CONFIG_STM32_OTGFS

    AHB3
    ----
    CONFIG_STM32_FSMC

    APB1
    ----
    CONFIG_STM32_TIM2
    CONFIG_STM32_TIM3
    CONFIG_STM32_TIM4
    CONFIG_STM32_TIM5
    CONFIG_STM32_TIM6
    CONFIG_STM32_TIM7
    CONFIG_STM32_TIM12
    CONFIG_STM32_TIM13
    CONFIG_STM32_TIM14
    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_I2C3
    CONFIG_STM32_CAN1
    CONFIG_STM32_CAN2
    CONFIG_STM32_DAC1
    CONFIG_STM32_DAC2
    CONFIG_STM32_PWR -- Required for RTC

    APB2
    ----
    CONFIG_STM32_TIM1
    CONFIG_STM32_TIM8
    CONFIG_STM32_USART1
    CONFIG_STM32_USART6
    CONFIG_STM32_ADC1
    CONFIG_STM32_ADC2
    CONFIG_STM32_ADC3
    CONFIG_STM32_SDIO
    CONFIG_STM32_SPI1
    CONFIG_STM32_SYSCFG
    CONFIG_STM32_TIM9
    CONFIG_STM32_TIM10
    CONFIG_STM32_TIM11

  Timer and I2C devices may need to the following to force power to be applied
  unconditionally at power up.  (Otherwise, the device is powered when it is
  initialized).

    CONFIG_STM32_FORCEPOWER

  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

  STM3240xxx 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

  STM3240xxx 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.

  STM3240xxx 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.

  STM3240xxx DMA Configuration

    CONFIG_SDIO_DMA - Support DMA data transfers.  Requires CONFIG_STM32_SDIO
      and CONFIG_STM32_DMA2.
    CONFIG_SDIO_PRI - Select SDIO interrupt prority.  Default: 128
    CONFIG_SDIO_DMAPRIO - Select SDIO DMA interrupt priority. 
      Default:  Medium
    CONFIG_SDIO_WIDTH_D1_ONLY - Select 1-bit transfer mode.  Default:
      4-bit transfer mode.

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

Each STM32F4Discovery configuration is maintained in a sudirectory and
can be selected as follow:

    cd tools
    ./configure.sh STM32F4Discovery/<subdir>
    cd -
    . ./setenv.sh

Where <subdir> is one of the following:

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

    CONFIG_STM32_CODESOURCERYW=y  : CodeSourcery under Windows


    If you use the Atollic toolchain, then the FPU test can be enabled in the
    examples/ostest by adding the following your NuttX configuration file:

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

     -CONFIG_STM32_CODESOURCERYW=y   : Disable the CodeSourcery toolchain
     +CONFIG_STM32_CODESOURCERYW=n

     -CONFIG_STM32_ATOLLIC_LITE=n   : Enable *one* the Atollic toolchains
      CONFIG_STM32_ATOLLIC_PRO=n
     -CONFIG_STM32_ATOLLIC_LITE=y   : The "Lite" version
      CONFIG_STM32_ATOLLIC_PRO=n    : The "Pro" version

     -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)

     -CONFIG_SCHED_WAITPID=y         : Enable the waitpid() API needed by the FPU test
     +CONFIG_SCHED_WAITPID=n

    The FPU test also needs to know the size of the FPU registers save area in
    bytes (see arch/arm/include/armv7-m/irq_lazyfpu.h):

     -CONFIG_EXAMPLES_OSTEST_FPUSIZE=(4*33)
 
  nsh:
  ---
    Configures the NuttShell (nsh) located at apps/examples/nsh.  The
    Configuration enables both the serial and telnet NSH interfaces.

    CONFIG_STM32_CODESOURCERYL=y  : CodeSourcery under Linux / Mac OS X

    NOTES:
    1. This example supports the PWM test (apps/examples/pwm) but this must
       be manually enabled by selecting:

       CONFIG_PWM=y              : Enable the generic PWM infrastructure
       CONFIG_STM32_TIM4=y       : Enable TIM4
       CONFIG_STM32_TIM4_PWM=y   : Use TIM4 to generate PWM output

       See also apps/examples/README.txt

       Special PWM-only debug options:

       CONFIG_DEBUG_PWM

    2. This example supports the Quadrature Encode test (apps/examples/qencoder)
       but this must be manually enabled by selecting:

       CONFIG_QENCODER=y         : Enable the generic Quadrature Encoder infrastructure
       CONFIG_STM32_TIM8=y       : Enable TIM8
       CONFIG_STM32_TIM2=n       : (Or optionally TIM2)
       CONFIG_STM32_TIM8_QE=y    : Use TIM8 as the quadrature encoder
       CONFIG_STM32_TIM2_QE=y    : (Or optionally TIM2)

       See also apps/examples/README.txt

       Special PWM-only debug options:

       CONFIG_DEBUG_QENCODER

    3. This example supports the watchdog timer test (apps/examples/watchdog)
       buty this must be manually enabled by selecting:

       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.