================
ST B-G474E-DPOW1
================

This page is for a port of NuttX to the ST Micro B-G474E-DPOW1
Discovery kit with STM32G474RE MCU. For more information about this board,
see:

  https://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-mpu-eval-tools/stm32-mcu-mpu-eval-tools/stm32-discovery-kits/b-g474e-dpow1.html

Status
======

This port boots NuttX through to a functional NSH prompt.

Development Environment
=======================

Toolchains
----------

An appropriate ARM toolchain is needed, such as the one built with the
customized NuttX buildroot or the ready-made GNU Tools for Arm Embedded
Processors.

Debugging
---------

The board incorporates a STLINK-V3E programmer/debugger accessible via the
Micro-USB Type B connector.

To debug with OpenOCD and arm-nuttx-eabi-gdb:

* Use 'make menuconfig' to set CONFIG_DEBUG_SYMBOLS and CONFIG_DEBUG_NOOPT.
  To see debug output, e.g., the "ABCDE" printed in __start(), also set
  CONFIG_DEBUG_FEATURES.

* Build NuttX.

* Flash the code using::

    $ openocd -f interface/stlink.cfg -f target/stm32g4x.cfg -c init \
    -c "reset halt" -c "flash write_image erase nuttx.bin 0x08000000"

NOTE: The above command might fail unless either: udev rules have been
configured on the development system (preferred) or the command is run as
root with 'sudo' (not encouraged). See:

  - https://openocd.org/doc/html/Running.html
  - https://forgge.github.io/theCore/guides/running-openocd-without-sudo.html

* Start GDB with::

  $ arm-nuttx-eabi-gdb -tui nuttx

* In GDB::

    (gdb) target remote localhost:3333
    (gdb) monitor reset halt
    (gdb) load

Hardware
========

MCU Clocking
------------

By default, the MCU on this board is clocked from the MCU's internal HSI
clock, and only this option is supported by software at this time.

If software support is added for it, the MCU could be clocked from the
following other sources: a 24 MHz oscillator on X2, MCO from STLINK-V3E, or
external clock from connector CN9, pin 26.

GPIOs
-----

Buttons
-------

The board has 5 user buttons in the form of a 4-direction "joystick" with a
selection button (pressing down on the "joystick").

LEDs
----

The board has 4 user LEDs.

RGB Power LED
-------------

The board has a super bright RGB power LED.

Caution: For eye safety, ensure that the power LED is covered by the
diffuser that comes installed over it.

Serial Consoles
===============

The MCU's USART3 is connected to the on-board STLINK-V3E and exposed to
the PC as a Virtual COM Port over the same Micro-USB Type B connection used
for programming/debugging.

On Debian Linux, this shows up as /dev/ttyACM0. Other operating systems may
differ.

FLASH Bootloader Support
========================

If implementing a FLASH bootloader, turn on Kconfig option CONFIG_STM32_DFU.
This option activates an alternate linker script, scripts/ld.script.dfu,
which causes NuttX to leave a gap at the start of FLASH, leaving that space
for the FLASH bootloader. See scripts/ld.script.dfu for details. It also
causes NuttX to relocate its vector table and possibly make other
adjustments.

One possible bootloader is STmicro's OpenBootloader "middleware" supplied
with STM32CubeG4 version 1.3.0. On the host (PC), it should be possible to
use STmicro's STM32CubeProgrammer or the stm32loader.py script from
https://github.com/jsnyder/stm32loader. That script can be invoked with
parameters such as::

    stm32loader.py -p /dev/ttyACM0 -a 0x08006000 -e -w -v -g 0x08006000 nuttx.bin

where the given address (0x08006000 in this case) must match the starting
address in scripts/ld.script.dfu.