STM32F4 UART Rx Interrupt Example Code

Question

I've been trying to implement a basic per-byte UART Rx Interrupt on a STM32F4 board using HAL skeleton code generated by STMCubeMX version 4.26.0

Quite simply - I want to receive a character in UART1 via an Rx interrupt and transmit it on UART 6

I have successfully implemented a polled version of what I want to achieve

    uint8_t in_usart1[10];

    HAL_StatusTypeDef usart1_status;

    usart1_status = HAL_UART_Receive(&huart1, in_usart1, 1, 1);

    if (usart1_status != HAL_TIMEOUT)
    {
            HAL_UART_Transmit(&huart6, in_usart1, 1, 100);
    }

I've enabled the UART 1 NVIC interrupt in STMCubeMX and stm32f4xx_it.c contains the IRQ handler which I've added my own user handler to:

void USART1_IRQHandler(void)
{
    /* USER CODE BEGIN USART1_IRQn 0 */

    /* USER CODE END USART1_IRQn 0 */
    HAL_UART_IRQHandler(&huart1);
    /* USER CODE BEGIN USART1_IRQn 1 */
    HAX_USART1_IRQHandler(&huart1); /* My Handler */
    /* USER CODE END USART1_IRQn 1 */
}

I've seen lot's of commentary about UART_Receive_IT() - but I suspect this is based on older versions of HAL due to UART_Receive_IT() being defined in stm32f4xx_hal_uart.c

My suspicion is that I need to enable to interrupt / clear the interrupt flag as when I debug, USART1_IRQHandler() is NEVER called

Does any one have any code that demonstrates what I am trying to achieve? My google-foo has failed me

EDIT: I've gotten a little closer... In main.c I added (comments are existing code)

  /* USER CODE BEGIN PV */
  uint8_t rx_buffer;
  /* USER CODE END PV */

  ...

  /* USER CODE BEGIN 2 */
  HAL_UART_Receive_IT(&huart1, (uint8_t *)rx_buffer, 10);
  /* USER CODE END 2 */

And then created:

  void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
  {
        if (huart->Instance == USART1)
        {
              HAL_UART_Transmit(&huart6, &rx_buffer, 1, 100);
        }
  }

Now the Rx interrupt gets fired - but it's a bit flakey on the USART6 Tx, and the Rx interrupt only gets fired once

Answer 1

Do not block HAL_UART_RxCpltCallback for a long time! Just set a flag and check it and then send data from the main function.

And rx_buffer is variable so correct call HAL_UART_Receive_IT(&huart1, &rx_buffer, 1);