Nucleo-F091RC README
====================

  This README file discusess the port of NuttX to the STMicro Nucleo-F091RC
  board.  That board features the STM32F091RCT6 MCU with 256KiB of FLASH
  and 32KiB of SRAM.

Contents
========

  - Nucleo-64 Boards
  - LEDs
  - Buttons
  - Serial Console
  - Configurations

Nucleo-64 Boards
================

  The Nucleo-F091RC is a member of the Nucleo-64 board family.  The Nucleo-64
  is a standard board for use with several STM32 parts in the LQFP64 package.
  Variants including:

    Order code    Targeted STM32
    ------------- --------------
    NUCLEO-F030R8 STM32F030R8T6
    NUCLEO-F070RB STM32F070RBT6
    NUCLEO-F072RB STM32F072RBT6
    NUCLEO-F091RC STM32F091RCT6
    NUCLEO-F103RB STM32F103RBT6
    NUCLEO-F302R8 STM32F302R8T6
    NUCLEO-F303RE STM32F303RET6
    NUCLEO-F334R8 STM32F334R8T6
    NUCLEO-F401RE STM32F401RET6
    NUCLEO-F410RB STM32F410RBT6
    NUCLEO-F411RE STM32F411RET6
    NUCLEO-F446RE STM32F446RET6
    NUCLEO-L053R8 STM32L053R8T6
    NUCLEO-L073RZ STM32L073RZT6
    NUCLEO-L152RE STM32L152RET6
    NUCLEO-L452RE STM32L452RET6
    NUCLEO-L476RG STM32L476RGT6

LEDs
====

  The Nucleo-64 board has one user controllable LED, User LD2.  This green
  LED is a user LED connected to Arduino signal D13 corresponding to STM32
  I/O PA5 (PB13 on other some other Nucleo-64 boards).

    - When the I/O is HIGH value, the LED is on
    - When the I/O is LOW, the LED is off

  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/stm32_autoleds.c. The LEDs are used to encode
  OS-related events as follows when the red LED (PE24) is available:

    SYMBOL                Meaning                   LD2
    -------------------  -----------------------  -----------
    LED_STARTED          NuttX has been started     OFF
    LED_HEAPALLOCATE     Heap has been allocated    OFF
    LED_IRQSENABLED      Interrupts enabled         OFF
    LED_STACKCREATED     Idle stack created         ON
    LED_INIRQ            In an interrupt            No change
    LED_SIGNAL           In a signal handler        No change
    LED_ASSERTION        An assertion failed        No change
    LED_PANIC            The system has crashed     Blinking
    LED_IDLE             MCU is is sleep mode       Not used

  Thus if LD2, NuttX has successfully booted and is, apparently, running
  normally.  If LD2 is flashing at approximately 2Hz, then a fatal error
  has been detected and the system has halted.

Buttons
=======

  B1 USER: the user button is connected to the I/O PC13 (pin 2) of the STM32
  microcontroller.

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

  USART1
  ------
  Pins and Connectors:

    RXD: PA10  D3  CN9 pin 3, CN10 pin 33
         PB7                  CN7  pin 21
    TXD: PA9   D8  CN5 pin 1, CN10 pin 21
         PB6   D10 CN5 pin 3, CN10 pin 17

  NOTE:  You may need to edit the include/board.h to select different USART1
  pin selections.

  TTL to RS-232 converter connection:

    Nucleo CN10 STM32F091RC
    ----------- ------------
    Pin 21 PA9  USART1_TX   *Warning you make need to reverse RX/TX on
    Pin 33 PA10 USART1_RX    some RS-232 converters
    Pin 20 GND
    Pin 8  U5V

  To configure USART1 as the console:

    CONFIG_STM32_USART1=y
    CONFIG_USART1_SERIALDRIVER=y
    CONFIG_USART1_SERIAL_CONSOLE=y
    CONFIG_USART1_RXBUFSIZE=256
    CONFIG_USART1_TXBUFSIZE=256
    CONFIG_USART1_BAUD=115200
    CONFIG_USART1_BITS=8
    CONFIG_USART1_PARITY=0
    CONFIG_USART1_2STOP=0

  USART2
  ------
  Pins and Connectors:

    RXD: PA3  To be provided
         PA15
         PD6
    TXD: PA2
         PA14
         PD5

  USART3
  ------
  Pins and Connectors:

    RXD: PB11 To be provided
         PC5
         PC11
         D9
    TXD: PB10
         PC4
         PC10
         D8

  See "Virtual COM Port" and "RS-232 Shield" below.

  USART3
  ------
  Pins and Connectors:

    RXD: PA1  To be provided
         PC11
    TXD: PA0
         PC10

  Virtual COM Port
  ----------------
  Yet another option is to use UART2 and the USB virtual COM port.  This
  option may be more convenient for long term development, but is painful
  to use during board bring-up.

  Solder Bridges.  This configuration requires:

  - SB62 and SB63 Open: PA2 and PA3 on STM32 MCU are disconnected to D1
    and D0 (pin 7 and pin 8) on Arduino connector CN9 and ST Morpho
    connector CN10.

  - SB13 and SB14 Closed:  PA2 and PA3 on STM32F103C8T6 (ST-LINK MCU) are
    connected to PA3 and PA2 on STM32 MCU to have USART communication
    between them. Thus SB61, SB62 and SB63 should be OFF.

  Configuring USART2 is the same as given above.

  Question:  What BAUD should be configure to interface with the Virtual
  COM port?  115200 8N1?

  Default
  -------
  As shipped, SB62 and SB63 are open and SB13 and SB14 closed, so the
  virtual COM port is enabled.

  RS-232 Shield
  -------------
  Supports a single RS-232 connected via

    Nucleo    STM32F4x1RE     Shield
    --------- --------------- --------
    CN9 Pin 1 PA3  USART2_RXD RXD
    CN9 Pin 2 PA2  USART2_TXD TXD

  Support for this shield is enabled by selecting USART2 and configuring
  SB13, 14, 62, and 63 as described above under "Virtual COM Port"

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

  Information Common to All Configurations
  ----------------------------------------
  Each configuration is maintained in a sub-directory and can be
  selected as follow:

    tools/configure.sh nucleo-f091rc:<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 oldconfig
    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 USART2, as described above under "Serial Console".  The
       elevant configuration settings are listed below:

         CONFIG_STM32_USART2=y
         CONFIG_STM32_USART2_SERIALDRIVER=y
         CONFIG_STM32_USART=y

         CONFIG_USART2_SERIALDRIVER=y
         CONFIG_USART2_SERIAL_CONSOLE=y

         CONFIG_USART2_RXBUFSIZE=256
         CONFIG_USART2_TXBUFSIZE=256
         CONFIG_USART2_BAUD=115200
         CONFIG_USART2_BITS=8
         CONFIG_USART2_PARITY=0
         CONFIG_USART2_2STOP=0

  3. All of these configurations are set up to build under Linux using the
     "GNU Tools for ARM Embedded Processors" that is maintained by ARM
     (unless stated otherwise in the description of the configuration).

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

     That toolchain selection can easily be reconfigured using
     'make menuconfig'.  Here are the relevant current settings:

     Build Setup:
       CONFIG_HOST_LINUX=y                 : Linux environment

     System Type -> Toolchain:
       CONFIG_ARM_TOOLCHAIN_GNU_EABI=y  : GNU ARM EABI toolchain

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

  nsh:

    Configures the NuttShell (nsh) located at examples/nsh.  This
    configuration is focused on low level, command-line driver testing.

    NOTES:

    1. This initial release of this configuration was very minimal, but
       also very small:

       $ size nuttx
          text    data     bss     dec     hex filename
         32000      92    1172   33264    81f0 nuttx

       The current version, additional features have been enabled:  board
       bring-up initialization, button support, the procfs file system,
       and NSH built-in application support.  The size increased as follows:

       $ size nuttx
          text    data     bss     dec     hex filename
         40231      92    1208   41531    a23b nuttx

       Those additional features cost about 8KiB FLASH.  I believe that is a
       good use of the STM32F091RC's FLASH, but if you interested in the
       more minimal configuration, here is what was changed:

       Removed

         CONFIG_BINFMT_DISABLE=y
         CONFIG_DISABLE_MOUNTPOINT=y
         CONFIG_NSH_DISABLE_CD=y

       Added:

         CONFIG_ARCH_BUTTONS=y
         CONFIG_ARCH_IRQBUTTONS=y

         CONFIG_BUILTIN=y

         CONFIG_FS_PROCFS=y
         CONFIG_NSH_PROC_MOUNTPOINT="/proc"

         CONFIG_BOARDCTL=y
         CONFIG_NSH_ARCHINIT=y
         CONFIG_NSH_BUILTIN_APPS=y

       Support for NSH built-in applications is enabled for future use.
       However, no built applications are enabled in this base configuration.

    2. C++ support for applications is NOT enabled.  That could be enabled
       with the following configuration changes:

         CONFIG_HAVE_CXX=y
         CONFIG_HAVE_CXXINITIALIZE=y

       And also support for C++ constructors under apps/platform.
