Unable to receive data over UART3

[smaiti]

Hi,

I have the following board : 
NUCLEO-F429ZI

The datasheet says that UART3 is the STLINK UART that can be used over USB.
I configured this UART but when I try to receive anything from the terminal that is connected to the UART com port, I don't see the interrupt being triggered.

The objective is to receive some data over UART3, process it, and send the processed data over UART6.

UART3 init in main.c

/**
  * @brief USART3 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_USART3_UART_Init(void)
{

  /* USER CODE BEGIN USART3_Init 0 */

  /* USER CODE END USART3_Init 0 */

  /* USER CODE BEGIN USART3_Init 1 */

  /* USER CODE END USART3_Init 1 */
  huart3.Instance = USART3;
  huart3.Init.BaudRate = 115200;
  huart3.Init.WordLength = UART_WORDLENGTH_8B;
  huart3.Init.StopBits = UART_STOPBITS_1;
  huart3.Init.Parity = UART_PARITY_NONE;
  huart3.Init.Mode = UART_MODE_TX_RX;
  huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart3.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART3_Init 2 */

  /* USER CODE END USART3_Init 2 */

}

 hal_msp.c 

/**
* @brief UART MSP Initialization
* This function configures the hardware resources used in this example
* @PAram huart: UART handle pointer
* @retval None
*/
void HAL_UART_MspInit(UART_HandleTypeDef* huart)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(huart->Instance==USART3)
  {
  /* USER CODE BEGIN USART3_MspInit 0 */

  /* USER CODE END USART3_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_USART3_CLK_ENABLE();

    __HAL_RCC_GPIOD_CLK_ENABLE();
    /**USART3 GPIO Configuration
    PD8     ------> USART3_TX
    PD9     ------> USART3_RX
    */
    GPIO_InitStruct.Pin = STLK_RX_Pin|STLK_TX_Pin;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART3;
    HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

    /* USART3 interrupt Init */
    HAL_NVIC_SetPriority(USART3_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(USART3_IRQn);
  /* USER CODE BEGIN USART3_MspInit 1 */

  /* USER CODE END USART3_MspInit 1 */
  }
  else if(huart->Instance==USART6)
  {
  /* USER CODE BEGIN USART6_MspInit 0 */

  /* USER CODE END USART6_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_USART6_CLK_ENABLE();

    __HAL_RCC_GPIOC_CLK_ENABLE();
    /**USART6 GPIO Configuration
    PC6     ------> USART6_TX
    PC7     ------> USART6_RX
    */
    GPIO_InitStruct.Pin = UART6_TX_Pin|UART6_RX_Pin;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF8_USART6;
    HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

    /* USART6 interrupt Init */
    HAL_NVIC_SetPriority(USART6_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(USART6_IRQn);
  /* USER CODE BEGIN USART6_MspInit 1 */

  /* USER CODE END USART6_MspInit 1 */
  }

}

Application code : 

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_USART3_UART_Init();
  MX_USART6_UART_Init();
  /* USER CODE BEGIN 2 */

  // Start receiving data in interrupt mode
  // HAL_UART_Receive(&huart3, rx_buffer, sizeof(rx_buffer),HAL_MAX_DELAY);

  if(HAL_UART_Receive_IT(&huart3, rx_buffer, sizeof(rx_buffer)) != HAL_OK)
  {
    Error_Handler();
  }

  // Transmit some data
//  char *message = "Hello World\n";

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

Callback to process the received cmd : 

// This function is called when data is received
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart->Instance == USART3)
    {
        // If data is received from UART3, send it to UART6
//        HAL_UART_Transmit(&huart6, rx_buffer, sizeof(rx_buffer), HAL_MAX_DELAY);
      if(HAL_UART_Transmit_IT(&huart6, rx_buffer, sizeof(rx_buffer)) != HAL_OK)
      {
        Error_Handler();
      }
        // Restart the interrupt reception on UART3
        HAL_UART_Receive_IT(&huart3, rx_buffer, sizeof(rx_buffer));
    }
}

I don't understand what is the problem.
Please help and ask for any other details.

[Pavel A.]

Please start from polling mode RX and TX first. Will it work?

HAL_UART_Receive(&huart3,...)
HAL_UART_Transmit(&huart6,...)

[smaiti]

Hi @Pavel A.,

Thanks for your reply.
I tried it but it also does not seem to be working.
I used HAL_DELAY_MAX in the time interval.
I also tested just the transmission on UART3 using the HAL_Transmit function in the while(1) loop.
I am getting the buffer on a terminal that is connected to this UART.
So not sure why this is happening.
Regards
smaiti

[Bob S]

How big is rx_buffer?  You do realize that you won't see the interrupt until you have received sizeof(rx_buffer) number of bytes, right?

Also, with your original code that uses interrupts, in the callback you start sending from rx_buffer, and then immediately start receiving new data into that same rx_buffer.  HAL_UART_Transmit_IT() returns immediately, before the data has been sent.

[Pavel A.]

Polling mode HAL_UART_Receive does not call HAL_UART_RxCpltCallback. Just send N characters from the terminal and it should return. If not, there's an electrical problem.

[smaiti · Accepted solution]

@Pavel A. @Bob S ,
Thanks for the insights.
I changed my strategy in the following ways : 

#define BUFFER_SIZE   1

//calling the following inside main()
  if(HAL_UART_Receive_IT(&huart3, &parentRx, BUFFER_SIZE) != HAL_OK)
  {
      Error_Handler();
  }

/**
 * @brief Callback function called when UART receive is complete.
 * 
 * @param huart Pointer to the UART handle structure.
 */
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart->Instance == USART3)
    {
      parentMessageSts = Motor_Cmd_Recieve_IT(parentRx, parentRxBuf,sizeof(parentRxBuf),&parentRxPtr);

      if(HAL_UART_Receive_IT(&huart3, &parentRx, BUFFER_SIZE) != HAL_OK)
      {
          Error_Handler();
      }
    }
}

// Motor_Cmd_Receive processes the incoming commands and stores it in a cmd buffe to be processed by another function
// This approach seems to be working.

[liaifat85]

Here is a similar thread: https://community.st.com/t5/stm32-mcus-products/uart3-can-t-receive-entire-data/td-p/174371