Cortex-M7 Toolchain & STM32 Skeleton

[alieissa-commits]

Description

Establish the local CMake toolchain for the ARM Cortex-M7 and write the low-level board enablement and initialization code for the STMicroelectronics STM32F767ZI-Nucleo-144 board.

This sets up the isolated foundation for the Network-Connected Environmental Station use-case, localizes all build settings to prevent merge conflicts, and aligns with the clean, decoupled board framework.

Checklist

1. Toolchain & Local Infrastructure

• Create a local board-specific CMake directory: STMicroelectronics/STM32F767ZI-Nucleo/cmake/.
• Implement local copies of the build helpers inside STMicroelectronics/STM32F767ZI-Nucleo/cmake/ (arm-gcc-cortex-toolchain.cmake and utilities.cmake) copied and customized from MXChip to achieve 100% target isolation.
• Create the local toolchain file STMicroelectronics/STM32F767ZI-Nucleo/cmake/arm-gcc-cortex-m7.cmake configuring compiler options specifically for the Cortex-M7 double-precision FPU (-mfloat-abi=hard -mfpu=fpv5-d16).
• Create localized discovery modules FindCMSIS.cmake and FindSTM32HAL.cmake inside the board's cmake/ folder, configured specifically to discover STM32F7 headers and HAL sources.

2. Directory Structure & SDK Setup

• Create the target directory structure directly in the root workspace: STMicroelectronics/STM32F767ZI-Nucleo/ (conforming to the <Vendor>/<Board> repository convention).
• Implement a script or command step to download/clone the lightweight vendor SDK folders (Drivers/CMSIS and Drivers/STM32F7xx_HAL_Driver) from the official STMicroelectronics/STM32CubeF7 repository into STMicroelectronics/STM32F767ZI-Nucleo/lib/stm32cubef7/.

3. Low-Level Startup & Hardware Abstraction

• Implement the startup/ files:
  • Add the official GCC linker script STM32F767ZITx_FLASH.ld defining Flash and SRAM boundaries.
  • Add the startup assembly startup_stm32f767xx.s defining the hardware vector table and redirecting to SystemInit.
  • Add the ThreadX low-level initialization assembly tx_initialize_low_level.S for Cortex-M7.
  • Add system_stm32f7xx.c to define standard clock-system parameters.

4. Board Initialization & Console Redirect

• Implement board_init.c and board_init.h to:
  • Configure the System Clock Tree (SystemClock_Config) to run at the maximum 216 MHz utilizing the ST-LINK 8 MHz oscillator bypass.
  • Initialize basic GPIOs (User LEDs, User Button).
• Implement console.c and console.h to initialize the virtual COM port UART (USART3 on pins PD8/PD9) and redirect printf outputs through nanoprintf.

5. Ethernet PHY Initialization

• Implement low-level Ethernet controller and RMII pin configurations.
• Write the initialization sequence for the on-board LAN8742A Ethernet PHY (setting up transceiver speeds, autonegotiation, and clock gating) to prepare for the NetX Duo IP stack.