Idle interrupt cannot be cleared

Debug environment

Single chip model ：stm32F103RCT6
The exception code is as follows . When using the serial port assistant to send a byte , Always enter idle interrupt , And the idle interrupt flag bit cannot be cleared .

void USART2_IRQHandler(void)
{
    
    if (UART_GET_FLAG(USART2, UART_FLAG_RXNE) != RESET)
    {
    
        fifoUart2.buf[fifoUart2.rcvCnt++] = USART2->DR;
        UART_CLEAR_FLAG(USART2, UART_FLAG_RXNE);
    }

    if (UART_GET_FLAG(USART2, UART_FLAG_IDLE) != RESET)
    {
    
        fifoUart2.parseFlag = RT_TRUE;
        UART_CLEAR_FLAG(USART2, UART_FLAG_IDLE);

        rt_event_send(rcvEvent, RCV_EVENT_UART2);
    }
}

Solution

Before clearing the idle terminal flag , Read it again DR Register value . From the description of this bit of the idle interrupt register in the manual, we can not see the principle .

void USART2_IRQHandler(void)
{
    
    uint32_t dr = 0;
    
    if (UART_GET_FLAG(USART2, UART_FLAG_RXNE) != RESET)
    {
    
        fifoUart2.buf[fifoUart2.rcvCnt++] = USART2->DR;
        UART_CLEAR_FLAG(USART2, UART_FLAG_RXNE);
    }

    if (UART_GET_FLAG(USART2, UART_FLAG_IDLE) != RESET)
    {
    
        dr = USART2->DR;
        fifoUart2.parseFlag = RT_TRUE;
        UART_CLEAR_FLAG(USART2, UART_FLAG_IDLE);

        rt_event_send(rcvEvent, RCV_EVENT_UART2);
    }
}