STM32G431 Core Board
The WeAct STM32G431 Core Board is a low-cost bare-bones STM32G431-based development board. See the STM32G431CB website [2] for more information about the MCU. More information about the board, including schematics, is available from the WeAct GitHub [1].
Modifications USB-C Power Delivery
The board does not support USB-C PD in its standard configuration. To enable USB-C PD, CC1 and CC2 need to be disconnected from their pull-down resistors and be connected to PB6 and PB4 respectively. Dead battery support requires PA9 and PA10 to be routed to CC1 and CC2. VBUS also needs to be connected to the MCU through a voltage divider.
The pull-downs are disconnected by removing the zero-Ohm resistors on SB8 and SB9 next to the USB-C connector. SB3, SB5, SB6, and SB7 then need to be closed to connect the CCx lines to the MCU. The voltage divider is connected to PB2 by closing SB4.
After these modifications have been made, PA9, PA10, PB2, PB4, and PB6 should be considered reserved for USB-C and not available for other applications.
Warning
The internal USB DFU boot loader may not work correctly with machines that respect USB PD signaling unless dead battery support has been enabled. A USB-C to USB-A adapter or programming using the SWD port can be used as a workaround.
Supported Features
The Zephyr weact_stm32g431_core board configuration supports the following hardware features:
Interface |
Controller |
Driver/Component |
|---|---|---|
NVIC |
on-chip |
nested vector interrupt controller |
UART |
on-chip |
serial port |
GPIO |
on-chip |
gpio |
ADC |
on-chip |
ADC Controller |
USB |
on-chip |
USB device |
UCPD |
on-chip |
ucpd |
The default configuration can be found in the defconfig file:
Pin Mapping
Default Zephyr Peripheral Mapping:
UART_2 TX/RX : PA2/PA3
UCPD1 CCx : PB6/PB4 (not connected by default)
UCPD1 DBCCx : PA9/PA10 (not connected by default)
BUTTON (User) : PC13
BUTTON (BOOT0) : PB8
LED0 : PC6
ADC (VBUS) : PB2
The ADC is disabled by default since the VBUS voltage divider is not connected in the board’s standard configuration.
Hardware Configuration
Solder bridge |
Default |
Description |
|---|---|---|
SB1/SB2 |
Open |
Route PC14/PC15 (LSE) to header |
SB6/SB7 |
Open |
Connect PB4/PB6 (UCPD1_CCx) to USB-C CCx pins |
SB3/SB5 |
Open |
Connect PA9/PA10 (UCPD1_DBCCx) to PB6/PB4 |
SB4 |
Open |
Connect PB2 to VBUS voltage divider |
SB8/SB9 |
Closed |
Connect USB-CCx to pull-down resistors |
SB10 |
Open |
VBUS protection diode bypass |
Clock Sources
The board has two external oscillators. The frequency of the slow clock (LSE) is 32.768 kHz. The frequency of the main clock (HSE) is 8 MHz.
The default configuration sources the system clock from the PLL, which is derived from HSE, and is set at 144 MHz. The 48 MHz clock used by the USB interface is derived from the PLL instead of the internal 48 MHz oscillator.
Programming and Debugging
The MCU is normally programmed using the ROM bootloader or the exposed SWD port.
Please note that some laptops may not detect the ROM bootloader correctly if the CCx pull-downs have been disconnected by opening SB8 and SB9 unless dead battery support has been enabled by closing SB3 and SB5. A USB-C to USB-A adapter can be used as a workaround if this is a problem.
Flashing an Application
Connect a USB-C cable and the board should power ON. Force the board into DFU mode by keeping the BOOT0 switch pressed while pressing and releasing the NRST switch.
The dfu-util runner is supported on this board and so a sample can be built and tested easily.
# From the root of the zephyr repository
west build -b weact_stm32g431_core samples/basic/blinky
west flash
Debugging
The board can be debugged by installing the included 100 mil (0.1 inch) header, and attaching an SWD debugger to the 3V3 (3.3V), GND, SCK, and DIO pins on that header.