Run STM32F103 from internal oscillator with PlatformIO (Arduino)? - arduino

Question

How can the STM32F103C8 be configured to run with internal RC oscillator / HSI & PLL, i.e. without external crystal oscillator (as present on the "blue pill" board) with the Arduino framework in PlatformIO?
https://docs.platformio.org/en/latest/boards/ststm32/bluepill_f103c8.html
https://docs.platformio.org/en/latest/boards/ststm32/genericSTM32F103C8.html
https://docs.platformio.org/en/latest/frameworks/arduino.html
platformio.ini:
[env:bluepill_f103c8]
platform = ststm32
board = bluepill_f103c8
#board = genericSTM32F103C8
#board_build.mcu = stm32f103c8t6
#board_build.f_cpu = 72000000L
framework = arduino
lib_deps = olikraus/U8g2 # ^2.28.7
upload_protocol = stlink

Answer 1

I dug around a bit in the PlatformIO directory.
The following paths are for "generic":
C:\Users\<user>\.platformio\platforms\ststm32\boards\genericSTM32F103C8.json
C:\Users\<user>\.platformio\packages\framework-arduinoststm32\variants\Generic_F103Cx\variant.cpp
Define your own system clock configuration in e.g. your main.cpp:
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_PeriphCLKInitTypeDef PeriphClkInit;
/* Initializes the CPU, AHB and APB busses clocks */
// RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
// RCC_OscInitStruct.HSEState = RCC_HSE_ON;
// RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
// RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI_DIV2;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
while (1);
}
/* Initializes the CPU, AHB and APB busses clocks */
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
| RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK) {
while (1);
}
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC ;
PeriphClkInit.AdcClockSelection = RCC_ADCPCLK2_DIV6;
PeriphClkInit.UsbClockSelection = RCC_USBCLKSOURCE_PLL_DIV1_5;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK) {
while (1);
}
}
The ini then is:
[env:bluepill_f103c8]
platform = ststm32
board = genericSTM32F103C8
framework = arduino
upload_protocol = stlink
lib_deps = olikraus/U8g2 # ^2.28.7
I'd recommend renaming the env to avoid confusion.
I have not yet verified the actual clock speed.
It should run at 36 MHz (8 MHz/2*9). The ini then needs `board_build.f_cpu = 36000000L`