USART escape sequence and interrupt.

[tonyyu]

Posted on September 05, 2013 at 18:30

Hi,

I am usingSTM324x9I-EVAL, which has a 32F439 chip with Keil tools chain and StdPeriph Lib, 1.2RC2, FreeRTOS 7.5.The following is the section of interrupt code.void USART1_IRQHandler(void){  portBASE_TYPE higherPriorityTask;    if(USART_GetITStatus(EVAL_COM1, USART_IT_RXNE) != RESET)  {    // Read one byte from the receive data register     // aRxBuffer[uhRxCounter++] = (USART_ReceiveData(EVAL_COM1) & 0x7F);    while (aRxByte != 0)      vTaskDelay(5);    aRxByte = USART_ReceiveData(EVAL_COM1);    if (xSemaphoreGiveFromISR(semaRXDAvail, &higherPriorityTask) == pdFALSE)      errorReg[EBUartRXSemaFail] |= EMUartRXSemaFail;  }......The program works well if the input is ''normal'' characters. However, when the received char is 0x1B (escape). Then it will wandering inside the stm32f4xx_usart.c and no longer getting any RXNE interrupt. What's the correct way to handle the escape sequence?Thanks,Sink.

[Tesla DeLorean]

Posted on September 05, 2013 at 18:53

This looks awesome

while (aRxByte != 0)       vTaskDelay(5); In the IRQ Handler do something and leave, don't be spinning in loops, or yielding to other tasks. Pretty much guaranteed to dead-lock. To process ESC sequences implement a simple state machine, and handle each character as it is received, buffer as required, flag for some deferred processing if required.

[tonyyu]

Posted on September 05, 2013 at 20:50

Yeah,

Thanks, I just found out that my RX task is fast enough to handle the escape sequence and got buffer overrun interrupt. Need to check ORE in the ISR.Sink

[tonyyu]

Posted on September 05, 2013 at 20:51

typo, 'is not'