micropython/ports/stm32/boards/VCC_GND_F407VE/board_init.c

#include "py/mphal.h"

void VCC_GND_F407VE_board_early_init(void) {
    // set SPI flash CS pin high
    mp_hal_pin_output(pin_A4);
    mp_hal_pin_write(pin_A4, 1);
}