xTaskCheckForTimeOut() function

// Driver library function used to receive uxWantedBytes from an Rx buffer // that is filled by a UART interrupt. If there are not enough bytes in the // Rx buffer then the task enters the Blocked state until it is notified that // more data has been placed into the buffer. If there is still not enough // data then the task re-enters the Blocked state, and xTaskCheckForTimeOut() // is used to re-calculate the Block time to ensure the total amount of time // spent in the Blocked state does not exceed MAX_TIME_TO_WAIT. This // continues until either the buffer contains at least uxWantedBytes bytes, // or the total amount of time spent in the Blocked state reaches // MAX_TIME_TO_WAIT – at which point the task reads however many bytes are // available up to a maximum of uxWantedBytes. size_t xUART_Receive( uint8_t *pucBuffer, size_t uxWantedBytes ) { size_t uxReceived = 0; TickType_t xTicksToWait = MAX_TIME_TO_WAIT; TimeOut_t xTimeOut; // Initialize xTimeOut. This records the time at which this function // was entered. vTaskSetTimeOutState( &xTimeOut ); // Loop until the buffer contains the wanted number of bytes, or a // timeout occurs. while( UART_bytes_in_rx_buffer( pxUARTInstance ) < uxWantedBytes ) { // The buffer didn't contain enough data so this task is going to // enter the Blocked state. Adjusting xTicksToWait to account for // any time that has been spent in the Blocked state within this // function so far to ensure the total amount of time spent in the // Blocked state does not exceed MAX_TIME_TO_WAIT. if( xTaskCheckForTimeOut( &xTimeOut, &xTicksToWait ) != pdFALSE ) { //Timed out before the wanted number of bytes were available, // exit the loop. break; } // Wait for a maximum of xTicksToWait ticks to be notified that the // receive interrupt has placed more data into the buffer. ulTaskNotifyTake( pdTRUE, xTicksToWait ); } // Attempt to read uxWantedBytes from the receive buffer into pucBuffer. // The actual number of bytes read (which might be less than // uxWantedBytes) is returned. uxReceived = UART_read_from_receive_buffer( pxUARTInstance, pucBuffer, uxWantedBytes ); return uxReceived; }