mkdir STM32_example_blink
cd STM32_example_blink

git -c http.sslVerify=false clone --recurse-submodules https://github.com/STMicroelectronics/STM32CubeF1

cat <<EOF >> blink.c #include "stm32f1xx.h"
#include "stm32f1xx_ll_bus.h"
#include "stm32f1xx_ll_gpio.h"

void GPIO_config(void) {
  LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_GPIOC);

  LL_GPIO_SetPinMode(GPIOC, LL_GPIO_PIN_13, LL_GPIO_MODE_OUTPUT);
  LL_GPIO_SetPinOutputType(GPIOC, LL_GPIO_PIN_13, LL_GPIO_OUTPUT_PUSHPULL);
  LL_GPIO_SetPinSpeed(GPIOC, LL_GPIO_PIN_13, LL_GPIO_SPEED_FREQ_LOW);
}

int main(void) {
  GPIO_config();

  for (;;) {
    LL_GPIO_ResetOutputPin(GPIOC, LL_GPIO_PIN_13);
    for (volatile int i = 0; i < 100000; i++);
    LL_GPIO_SetOutputPin(GPIOC, LL_GPIO_PIN_13);
    for (volatile int i = 0; i < 100000; i++);
  }

}
EOF


arm-none-eabi-gcc -DSTM32F103xB -I./STM32CubeF1/Drivers/CMSIS/Device/ST/STM32F1xx/Include -I./STM32CubeF1/Drivers/CMSIS/Include -I./STM32CubeF1/Drivers/STM32F1xx_HAL_Driver/Inc -mcpu=cortex-m3 -mthumb -std=c99 -ffunction-sections -fdata-sections -c blink.c

arm-none-eabi-gcc -DSTM32F103xB -I./STM32CubeF1/Drivers/CMSIS/Device/ST/STM32F1xx/Include -I./STM32CubeF1/Drivers/CMSIS/Include -I./STM32CubeF1/Drivers/STM32F1xx_HAL_Driver/Inc -mcpu=cortex-m3 -mthumb -std=c99 -ffunction-sections -fdata-sections -c ./STM32CubeF1/Drivers/CMSIS/Device/ST/STM32F1xx/Source/Templates/system_stm32f1xx.c

arm-none-eabi-gcc -x assembler-with-cpp -mthumb -c ./STM32CubeF1/Drivers/CMSIS/Device/ST/STM32F1xx/Source/Templates/gcc/startup_stm32f103xb.s

arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -std=c99 -ffunction-sections -fdata-sections -pipe --specs=nosys.specs -Wl,--gc-sections -ffreestanding "-T./STM32CubeF1/Drivers/CMSIS/Device/ST/STM32F1xx/Source/Templates/gcc/linker/STM32F103XB_FLASH.ld" blink.o startup_stm32f103xb.o system_stm32f1xx.o -o blink.elf

arm-none-eabi-objcopy -Oihex blink.elf blink.hex