Hands-On RTOS with Microcontrollers

USART2_IRQHandler

Here is the code for USART2_IRQHandler:

void USART2_IRQHandler( void ){    portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;    SEGGER_SYSVIEW_RecordEnterISR();    //error flag clearing omitted for brevity    if( USART2->ISR & USART_ISR_RXNE_Msk)    {        uint8_t tempVal = (uint8_t) USART2->RDR;        if(rxInProgress)        {            xQueueSendFromISR(uart2_BytesReceived, &tempVal,                               &xHigherPriorityTaskWoken);      }      SEGGER_SYSVIEW_RecordExitISR();      portYIELD_FROM_ISR(xHigherPriorityTaskWoken);}

Let's take a closer look at each component of the ISR:

•  The USART registers are directly read to determine whether or not the receive not empty (RXNE) is set. If it is, the contents of the receive data register (RDR) are stored to a temporary variable (tempVal)—this read clears ...