UART receive interrupt

[DAyva]

I'm trying to take input from user via serial port. I use STM32's USART1_IRQHandler and sscanf functions. Although I can print message on the port by using sprintf, I can't take input with sscanf. It doesn't wait for input and assigns a value I can't understand. I shared the code below. How may I solve this issue?

char uartTxBuffer3[50];

memset(uartTxBuffer3, 0, 50);

sprintf(uartTxBuffer3, "\nEnter frequency: \n");

BSP_Uart_Transmit(uartTxBuffer3, sizeof(uartTxBuffer3));

char buffer [50];

char freqaddress[50];

int inputfreq;

USART1_IRQHandler();

//USART_ClearITPendingBit(USART1, USART_IT_RXNE);

sscanf(buffer,"%s %i",freqaddress,&inputfreq);

char uartTxBuffer4[100];

memset(uartTxBuffer4, 0, 100);

sprintf (uartTxBuffer4, "Frequency: %i",(int)inputfreq);

[Tesla DeLorean]

You generally don't call USART1_IRQHandler() in-line from your code. That's not how interrupts work. The micro-controller calls the handler when the interrupting device signals.

You'd need the handler to accumulate data, that arrives a byte at a time.

You'd need to wait for it to actually fill a string buffer against which to run sscanf(), the data would need to be NUL terminated.

[DAyva]

Thank you for your answer. I wonder how can I call the handler in the main function? My handler function is attached below, written by another engineer and I need to set it right to establish the communication.

void USART1_IRQHandler(void) //usart irq

{

  char chr;

  if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)

  {

    uartRxBuffer[uartIndex] = USART_ReceiveData(USART1);

    uartIndex++;

    if(uartIndex == 342)

    {

      uartIndex = 0;

      uartReceiveCallBack(uartRxBuffer);

    }

  }

  if(USART_GetITStatus(USART3, USART_IT_TXE) != RESET)

  {

  }

}

I can't figure out how to use this function in the main to use scanf. Please help.

[Tesla DeLorean]

You'd probably want to have the interrupt code check for patterns and resync, at some point a 342 byte byte might get misaligned.

The current routine calls a callback function with the data.

You'd need to copy the data to a buffer that isn't transient, and also make sure it is NUL terminated.

You could then flag the availability of data via a volatile variable, which the main() loop could wait on.