STM32L562 UART Data Rx packet loss

[414D414E]

Hi,

I am using USART4 in STM32L562E-DK eval board. with given configuration.

In which I am able to transmit the data correctly on TX based on which UART slave device is sending back the 4 bytes ACK and 16 bytes RESPONSE.

Using following code

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
  if (huart->Instance == UART4) // check correct UART
  {
    // Store received byte
    //UART_Print("bytercv\r\n");
    if (rxIndex < RX_BUFFER_SIZE_4)
    {
      rxBuffer4[rxIndex++] = rxData;
    }

    // Check if done
    if (rxIndex >= rxTargetLen)
    {
      rxComplete = 1; // Mark reception complete
    }
    else
    {
      // Keep receiving next byte
      HAL_UART_Receive_IT(&huart4, &rxData, 1);
    }
  }
}

I am able to receive the ACK but after some time when I read the RESPONSE there is not data available.

If I am reading only 4bytes of data what happens to remaining data is it loss?

Or I have to use FIFO based UART implementation.

Regards,

Aman 

---

Edited to apply source code formatting - please see How to insert source code for future reference.

[TDK]

> If I am reading only 4bytes of data what happens to remaining data is it loss?

If you don't read out a byte before a new byte comes in, an overrun occurs and the new data will be lost. The peripheral will need to have the OVR flag cleared before it will receive new data.

[414D414E]

Hi,

On probing the RX signal,

I am receiving 4 bytes and after approx. 500us I am receiving other 15 bytes of data. 

On reading 4 bytes I am getting the desired data after processing; I am reading next 15 bytes of data during which HAL_BUSY error is received.

Will I need to clear OVR flag manually after reading 4 bytes.

Also, UART1 interface used for user input receiving data without clearing OVR flag, using same interrupt based HAL_UART_Recived_IT function.

Regards, 

Aman

[TDK]

> Will I need to clear OVR flag manually after reading 4 bytes.

Are more bytes coming in which you aren't ready for?

HAL_BUSY indicates the peripheral is already waiting for data. You shouldn't be calling HAL_UART_Receive_IT more than once until it finishes.

[Karl Yamashita]

If the slave is sending in packets, then use HAL_UARTEx_ReceiveToIdle_DMA and HAL_UARTEx_RxEventCallback for idle event.

On each packet sent, there will be an idle state which will interrupt. By using a queue, you can separate each packet in it's own queue for easing processing. If you don't want to use DMA, you can use HAL_UARTEx_ReceiveToIdle_IT without DMA. 

See this example project https://github.com/karlyamashita/Nucleo-G071RB_UART_DMA_Idle_Circular/wiki

[luguanluguanlulushijiandaole]

Can i see the size of rxbuffer4? and if you clear the index? if index more than size , will it receive(handle the data) the data read, so i think you can have a fifo, as soon as data come, you just read it to fifo, and have a process in main while and deal those data in fifo, in this case you will not omission any data.