STM32 receives interrupt service function print function and causes errors

In the interrupt service function, the printing function must not be used, because the printing function takes too long, which will cause the interrupt service function to not exit for a long time, which will cause some unexpected results.

For example, in the serial port interrupt:

void USART2_IRQHandler(void)

{

    unsigned char res;

    uint16_t uhdata;

    uint16_t uhMask = (&huart2)->Mask;

    //if(USART2->ISR&(1<<5))//?????

    if(((READ_REG((&huart2)->Instance->ISR) & USART_ISR_RXNE) != RESET) && ((READ_REG((&huart2)->Instance->CR1) & USART_CR1_RXNEIE) != RESET))

    {    

        res = 0;

        res = USART2->RDR; 

        printf("\r\n USART2 IRQ....%x %d \r\n",res,cnt2++);        

        if('$' == res)

        {cnt =0;memset(USART2_RMCtmp_BUF,0,256);}

        USART2_RMCtmp_BUF[cnt] = res;

        if((cnt>=3) && (USART2_RMCtmp_BUF[3] == 'R'))

        {

            USART2_RMC_BUF[cnt] = res;

        }    

        cnt++;                                              

    } 

}

result:

You can see that the received result is 0d 0a, and then nothing. Because the printing function takes too long, the value in the RDR register is not read immediately, which will cause an overflow error, and thus the receiving interrupt cannot be entered to process data. When the printing function is removed, everything is normal.

Therefore, do not perform time-consuming operations in the interrupt service function, especially in the receiving interrupt service function.