I am using the UART of an STM32F103C8T6. When selecting the Asynchronous mode via the CubeMX everything works fine using either of the functions HAL_UART_Transmit_IT() and HAL_UART_Transmit(). I am using a Baud Rate of 250kBits/s (for DMX).
When I set the mode to LIN and don't change anything else, the baud rate which the STM is sending at isn't correct anymore (measured with an oscilloscope), even though I didn't change it in my configuration.
Interestingly when I set the baud rate to (the wrong value of) ~230kBits/s it sends at approximately the correct data rate again. This is when using HAL_UART_Transmit_IT(). When using HAL_UART_Transmit(), I need to set it to ~210kBits/s to achieve a decently correct baud rate.
What could be the cause of this problem? Just changing it to a wrong value such that it somehow kinda works without knowing what's going on is a bit unsettling and isn't what I'd consider a great solution. Also, the receiver doesn't really decode the data correctly.
Thanks for your help.
The code:
main.c (in Asynchronous mode):
/* USER CODE BEGIN Header */ /** ****************************************************************************** * @file : main.c * @brief : Main program body ****************************************************************************** * @attention * * Copyright (c) 2024 STMicroelectronics. * All rights reserved. * * This software is licensed under terms that can be found in the LICENSE file * in the root directory of this software component. * If no LICENSE file comes with this software, it is provided AS-IS. * ****************************************************************************** */ /* USER CODE END Header */ /* Includes ------------------------------------------------------------------*/ #include "main.h" #include "usb_device.h" /* Private includes ----------------------------------------------------------*/ /* USER CODE BEGIN Includes */ /* USER CODE END Includes */ /* Private typedef -----------------------------------------------------------*/ /* USER CODE BEGIN PTD */ /* USER CODE END PTD */ /* Private define ------------------------------------------------------------*/ /* USER CODE BEGIN PD */ /* USER CODE END PD */ /* Private macro -------------------------------------------------------------*/ /* USER CODE BEGIN PM */ /* USER CODE END PM */ /* Private variables ---------------------------------------------------------*/ TIM_HandleTypeDef htim2; UART_HandleTypeDef huart2; /* USER CODE BEGIN PV */ /* USER CODE END PV */ /* Private function prototypes -----------------------------------------------*/ void SystemClock_Config(void); static void MX_GPIO_Init(void); static void MX_TIM2_Init(void); static void MX_USART2_UART_Init(void); /* USER CODE BEGIN PFP */ /* USER CODE END PFP */ /* Private user code ---------------------------------------------------------*/ /* USER CODE BEGIN 0 */ uint8_t DMX_state = 0; // 0: idle (ready to send), 1: data is available, 2: break on DMX line, 3: mark after break on DMX line, 4: sending data uint8_t DMX_loop_counter = 0; uint8_t DMX_data[513]; // first byte is the zero-byte/ start byte /* USER CODE END 0 */ /** * @brief The application entry point. * @retval int */ int main(void) { /* USER CODE BEGIN 1 */ /* USER CODE END 1 */ /* MCU Configuration--------------------------------------------------------*/ /* Reset of all peripherals, Initializes the Flash interface and the Systick. */ HAL_Init(); /* USER CODE BEGIN Init */ /* USER CODE END Init */ /* Configure the system clock */ SystemClock_Config(); /* USER CODE BEGIN SysInit */ /* USER CODE END SysInit */ /* Initialize all configured peripherals */ MX_GPIO_Init(); MX_TIM2_Init(); MX_USART2_UART_Init(); MX_USB_DEVICE_Init(); /* USER CODE BEGIN 2 */ /* USER CODE END 2 */ /* Infinite loop */ /* USER CODE BEGIN WHILE */ while (1) { /* USER CODE END WHILE */ /* USER CODE BEGIN 3 */ } /* USER CODE END 3 */ } /** * @brief System Clock Configuration * @retval None */ void SystemClock_Config(void) { RCC_OscInitTypeDef RCC_OscInitStruct = {0}; RCC_ClkInitTypeDef RCC_ClkInitStruct = {0}; RCC_PeriphCLKInitTypeDef PeriphClkInit = {0}; /** Initializes the RCC Oscillators according to the specified parameters * in the RCC_OscInitTypeDef structure. */ RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE; 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.PLLMUL = RCC_PLL_MUL9; if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) { Error_Handler(); } /** Initializes the CPU, AHB and APB buses 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) { Error_Handler(); } PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USB; PeriphClkInit.UsbClockSelection = RCC_USBCLKSOURCE_PLL_DIV1_5; if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK) { Error_Handler(); } } /** * @brief TIM2 Initialization Function * @param None * @retval None */ static void MX_TIM2_Init(void) { /* USER CODE BEGIN TIM2_Init 0 */ /* USER CODE END TIM2_Init 0 */ TIM_ClockConfigTypeDef sClockSourceConfig = {0}; TIM_MasterConfigTypeDef sMasterConfig = {0}; /* USER CODE BEGIN TIM2_Init 1 */ /* USER CODE END TIM2_Init 1 */ htim2.Instance = TIM2; htim2.Init.Prescaler = 71; htim2.Init.CounterMode = TIM_COUNTERMODE_UP; htim2.Init.Period = 11; htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1; htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE; if (HAL_TIM_Base_Init(&htim2) != HAL_OK) { Error_Handler(); } sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL; if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK) { Error_Handler(); } sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET; sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE; if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK) { Error_Handler(); } /* USER CODE BEGIN TIM2_Init 2 */ /* USER CODE END TIM2_Init 2 */ } /** * @brief USART2 Initialization Function * @param None * @retval None */ static void MX_USART2_UART_Init(void) { /* USER CODE BEGIN USART2_Init 0 */ /* USER CODE END USART2_Init 0 */ /* USER CODE BEGIN USART2_Init 1 */ /* USER CODE END USART2_Init 1 */ huart2.Instance = USART2; huart2.Init.BaudRate = 250000; huart2.Init.WordLength = UART_WORDLENGTH_8B; huart2.Init.StopBits = UART_STOPBITS_2; huart2.Init.Parity = UART_PARITY_NONE; huart2.Init.Mode = UART_MODE_TX_RX; huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE; huart2.Init.OverSampling = UART_OVERSAMPLING_16; if (HAL_UART_Init(&huart2) != HAL_OK) { Error_Handler(); } /* USER CODE BEGIN USART2_Init 2 */ /* USER CODE END USART2_Init 2 */ } /** * @brief GPIO Initialization Function * @param None * @retval None */ static void MX_GPIO_Init(void) { GPIO_InitTypeDef GPIO_InitStruct = {0}; /* GPIO Ports Clock Enable */ __HAL_RCC_GPIOD_CLK_ENABLE(); __HAL_RCC_GPIOA_CLK_ENABLE(); /*Configure GPIO pin Output Level */ HAL_GPIO_WritePin(TRANSISTOR_GPIO_Port, TRANSISTOR_Pin, GPIO_PIN_RESET); /*Configure GPIO pin : TRANSISTOR_Pin */ GPIO_InitStruct.Pin = TRANSISTOR_Pin; GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP; GPIO_InitStruct.Pull = GPIO_NOPULL; GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW; HAL_GPIO_Init(TRANSISTOR_GPIO_Port, &GPIO_InitStruct); } /* USER CODE BEGIN 4 */ void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef* htim) { // htim2.Init.Prescaler = 71; // prescale 72 MHz to 1 MHz -> every 1 microsecond // htim2.Init.Period = 11; // count from 0 to 11 -> 12 microseconds // break for 8 periods (8*12=96) (count to 8), and mark after break for one period (just wait for next loop execution) if (DMX_state == 1){ // 0: idle (ready to send), 1: data is available, 2: break on DMX line, 3: mark after break on DMX line, 4: sending data HAL_GPIO_WritePin(TRANSISTOR_GPIO_Port, TRANSISTOR_Pin, 1); // pulls low -> break DMX_loop_counter = 0; DMX_state = 2; } else if (DMX_state == 2){ if (DMX_loop_counter < 8) { // wait 8 loop executions DMX_loop_counter++; } else { HAL_GPIO_WritePin(TRANSISTOR_GPIO_Port, TRANSISTOR_Pin, 0); // stops pulling low -> mark after break DMX_state = 3; } } else if (DMX_state == 3){ HAL_UART_Transmit_IT(&huart2, DMX_data, sizeof(DMX_data)); HAL_TIM_Base_Stop_IT(&htim2); DMX_state = 4; } } void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart) { DMX_state = 0; } /* USER CODE END 4 */ /** * @brief This function is executed in case of error occurrence. * @retval None */ void Error_Handler(void) { /* USER CODE BEGIN Error_Handler_Debug */ /* User can add his own implementation to report the HAL error return state */ __disable_irq(); while (1) { } /* USER CODE END Error_Handler_Debug */ } #ifdef USE_FULL_ASSERT /** * @brief Reports the name of the source file and the source line number * where the assert_param error has occurred. * @param file: pointer to the source file name * @param line: assert_param error line source number * @retval None */ void assert_failed(uint8_t *file, uint32_t line) { /* USER CODE BEGIN 6 */ /* User can add his own implementation to report the file name and line number, ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */ /* USER CODE END 6 */ } #endif /* USE_FULL_ASSERT */ In the usbd_cdc_if.c, I added something in CDC_Receive_FS():
static int8_t CDC_Receive_FS(uint8_t* Buf, uint32_t *Len) { /* USER CODE BEGIN 6 */ USBD_CDC_SetRxBuffer(&hUsbDeviceFS, &Buf[0]); USBD_CDC_ReceivePacket(&hUsbDeviceFS); uint32_t length = (uint32_t) *Len; uint8_t buffer[length]; memcpy(buffer, Buf, length); extern uint8_t DMX_data[513]; extern uint8_t DMX_state; extern htim2; if (length >= 1) { if ((buffer[0] == 0x80) && (DMX_state == 0) && (length >= 2)) { memset(DMX_data, 0x00, sizeof(DMX_data)); memcpy(&DMX_data[1], &buffer[1], (length-1)); HAL_TIM_Base_Start_IT(&htim2); DMX_state = 1; } } return (USBD_OK); /* USER CODE END 6 */ } I also enabled the Interrupts for TIM2 and USART2.
