Cannot transmit every characters through UART

Question

I am using stm32f0 MCU.

I would like to transmit every single byte received from the uart out of the uart. I am enabling an interrupt on every byte received from uart.

My code is quite simple.

uint8_t Rx_data[5]; 

//Interrupt callback routine
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart->Instance == USART1)  //current UART
    {
        HAL_UART_Transmit(&huart1, &Rx_data[0], 1, 100);        
        HAL_UART_Receive_IT(&huart1, Rx_data, 1);   //activate UART receive interrupt every time on receiving 1 byte
    }
}

My PC transmits ASCII 12345678 to stm32. If things work as expected, the PC should be receiving 12345678 back. However, the PC receives 1357 instead. What is wrong with the code?

Answer 1

Reenabling interrupts may be inefficient. With a couple of modifications it is possible to keep the interrupt active without needing to write the handler all over again. See the example below altered from the stm32cubemx generator.

/**
* @brief This function handles USART3 to USART6 global interrupts.
*/
void USART3_6_IRQHandler(void)
{
  InterruptGPS(&huart5);
}

void InterruptGPS(UART_HandleTypeDef *huart) {
    uint8_t rbyte;
    if (huart->Instance != USART5) {
        return;
    }
    /* UART in mode Receiver ---------------------------------------------------*/
    if((__HAL_UART_GET_IT(huart, UART_IT_RXNE) == RESET) || (__HAL_UART_GET_IT_SOURCE(huart, UART_IT_RXNE) == RESET)) {
        return;
    }
    rbyte = (uint8_t)(huart->Instance->RDR & (uint8_t)0xff);
    __HAL_UART_SEND_REQ(huart, UART_RXDATA_FLUSH_REQUEST);

    // do your stuff

}

static void init_gps() {
    __HAL_UART_ENABLE_IT(&huart5, UART_IT_RXNE);
}