IDLE flag problem with uart?

Question

void USART2_IRQHandler(void)
 
{
 
 /* USER CODE BEGIN USART2_IRQn 0 */
 
  /* UART IDLE Interrupt */
 
    if(__HAL_UART_GET_FLAG(&huart2, UART_FLAG_IDLE) == SET)  
 
    {
 
     __HAL_UART_CLEAR_IDLEFLAG(&huart2);
 print("time %d",timeCounter");
receivedDataFlag = 1;

 
}
 
}

When I use the this function check line idle states and decide the data received or not received. But this interrup trigger while transmitting. How can I seperate receive data line idle and receive idle ?

I want to trigger just receive data line idle, how can I do that ? What other register should I look at?

I get very interesting result,

Sender send every 100 ms data to my device;

If I use the only receive DMA functions; time return 10, 110, 220,330 (Idle states working)

But If I received than after transmit data with uart this times values return 10,13,15,... a mean transmit function cahnge the line idle state, how is the possible ? IS the UART_FLAG_IDLE related only rx?

EDIT: By the way I am using rs485 so when I start to transmitting, I set to tranceiver transmitter mode so Sender side receiver mode so my MCU does decide to IDLE this state ? is that possible? How can I protect this situation?

When I start the transmition mode after received data, then completed callback call, When I call the HAL_UART_Receive_DMA(&huart2,(uint8_t*)dma_rx_buf,DMA_BUF_SIZE); function IDLE interrupt trigger every 5 ms but data sending timeout 100 ms

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
 

  HAL_UART_DMAStop(&huart2);
  dmaTransmitCompletedFlag = 1;
  RS485_Set_Receive_Mode();
  HAL_UART_Receive_DMA(&huart2,(uint8_t*)dma_rx_buf,DMA_BUF_SIZE);
  waitForTransmittingData = 0;

}

Answer 1

That interrupt is used for both transmit and receive.

The IDLE is relevant only to reception, it means there is at least one full frame of idle detected.

Using print in an interrupt is unwise, espcially if the print uses the same UART for which the interrupt is.

Answer 2

That IRQ is dedicated for USART2, but it gets called for every enabled interrupt associated with USART2. That means that the handler needs to check and handle every enabled interrupt signal. For STM32 USART, that includes signals fundamental to interrupt driven UART like TXNE and RXNE, as well as error signals, IDLE, etc.

The IDLE signal is for framing multi-byte receptions (a common issue for USART, especially in noisy environments). It gets asserted when the receive line has been asserted high (or 'idle') for some debounce time (determined by the baud rate/oversampling settings), after that line has been active (during reception of a group of one or more bytes). This is useful because you can use it to reset your receive buffer back to the '0' index, so that the next frame is lined up properly (even if too few or too many bytes were received in the current frame). Normally you have to implement this kind of logic with a dedicated timer peripheral, but STM32 conveniently packs it into their USART peripherals (although it's not supported by the native HAL driver).

If you really want only the idle signal to trigger an interrupt, you'll need to manually disable every other interrupt signal. If you want a useful interrupt-driven UART receiver, I don't suggest you do that.

Answer 3

From one of your previous questions I gave you some links, where this is implemented.

Source code

USART3_IRQHandler(void) {
    /* Check for IDLE line interrupt */
    if (LL_USART_IsEnabledIT_IDLE(USART3) && LL_USART_IsActiveFlag_IDLE(USART3)) {
        LL_USART_ClearFlag_IDLE(USART3);        /* Clear IDLE line flag */
        usart_rx_check();                       /* Check for data to process */
    }

    /* Implement other events when needed */
}