@maxgerhardt I made some progress but also went backwards too. I went back to using Arduino and thought that perhaps this was a bug with STM32Duino but it turned out that if I used the clock configuration from Adafruit’s STM32F405 Feather board then writing to the default Serial port worked, as well as using Serial4. What’s odd about that is that they have an external crystal on their board and I do not. It doesn’t seem right to me but I can use PLLM = 8 or PLLM =16 and both work in the Arduino “IDE”
//Adafruit Clock
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {};
/** Configure the main internal regulator output voltage
*/
__HAL_RCC_PWR_CLK_ENABLE();
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
/** Initializes the CPU, AHB and APB busses clocks
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = 16; //Adafruit uses 8
RCC_OscInitStruct.PLL.PLLN = 168;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
Error_Handler();
}
/** 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_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK) {
Error_Handler();
}
}
I tried copying over the variant.cpp into the PIO directory but that didn’t work. I’ve gone back to your HAL code and for some reason I can’t get that to work now yet Arduino works as well as code from STM32CubeIDE. I’ve deleted .pio and .vscode directories and restarted VS Code many times. If I hover over the Serial line in the code I can see that it is being mapped to Serial4 so I’m guessing somehow this is all related to clock configuration and something different between PIO and Arduino?