Minor updates to comment block for xTaskCheckForTimeOut().

pull/5/head
Richard Barry 5 years ago
parent dfc1bf8ec3
commit 62b413627a

@ -2201,6 +2201,103 @@ uint32_t ulTaskNotifyTake( BaseType_t xClearCountOnExit, TickType_t xTicksToWait
*/
BaseType_t xTaskNotifyStateClear( TaskHandle_t xTask );
/**
* task.h
* <pre>void vTaskSetTimeOutState( TimeOut_t * const pxTimeOut )</pre>
*
* Capture the current time for future use with xTaskCheckForTimeOut().
*
* @param pxTimeOut Pointer to a timeout object into which the current time
* is to be captured. The captured time includes the tick count and the number
* of times the tick count has overflowed since the system first booted.
* \defgroup vTaskSetTimeOutState vTaskSetTimeOutState
* \ingroup TaskCtrl
*/
void vTaskSetTimeOutState( TimeOut_t * const pxTimeOut ) PRIVILEGED_FUNCTION;
/**
* task.h
* <pre>BaseType_t xTaskCheckForTimeOut( TimeOut_t * const pxTimeOut, TickType_t * const pxTicksToWait );</pre>
*
* Determines if pxTicksToWait ticks has passed since a time was captured
* using a call to vTaskSetTimeOutState(). The captured time includes the tick
* count and the number of times the tick count has overflowed.
*
* @param pxTimeOut The time status as captured previously using
* vTaskSetTimeOutState. If the timeout has not yet occurred, it is updated
* to reflect the current time status.
* @param pxTicksToWait The number of ticks to check for timeout i.e. if
* pxTicksToWait ticks have passed since pxTimeOut was last updated (either by
* vTaskSetTimeOutState() or xTaskCheckForTimeOut()), the timeout has occurred.
* If the timeout has not occurred, pxTIcksToWait is updated to reflect the
* number of remaining ticks.
*
* @return If timeout has occurred, pdTRUE is returned. Otherwise pdFALSE is
* returned and pxTicksToWait is updated to reflect the number of remaining
* ticks.
*
* @see https://www.freertos.org/xTaskCheckForTimeOut.html
*
* Example Usage:
* <pre>
// 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;
}
</pre>
* \defgroup xTaskCheckForTimeOut xTaskCheckForTimeOut
* \ingroup TaskCtrl
*/
BaseType_t xTaskCheckForTimeOut( TimeOut_t * const pxTimeOut, TickType_t * const pxTicksToWait ) PRIVILEGED_FUNCTION;
/*-----------------------------------------------------------
* SCHEDULER INTERNALS AVAILABLE FOR PORTING PURPOSES
*----------------------------------------------------------*/
@ -2317,90 +2414,6 @@ TickType_t uxTaskResetEventItemValue( void ) PRIVILEGED_FUNCTION;
*/
TaskHandle_t xTaskGetCurrentTaskHandle( void ) PRIVILEGED_FUNCTION;
/*
* Capture the current time status for future reference.
*
* @param[out] pxTimeOut Pointer to a timeout object into which the current
* time status is to be captured.
*/
void vTaskSetTimeOutState( TimeOut_t * const pxTimeOut ) PRIVILEGED_FUNCTION;
/*
* Compare the time status now with the one previously captured using
* vTaskSetTimeOutState to check if the timeout has occurred.
*
* @param[in/out] pxTimeOut The time status as captured previously using
* vTaskSetTimeOutState. If the timeout has not yet occurred, it is updated
* to reflect the current time status.
* @param[in/out] pxTicksToWait The number of ticks to check for timeout i.e. if
* pxTicksToWait ticks have passed since pxTimeOut was last updated (either by
* vTaskSetTimeOutState or xTaskCheckForTimeOut), the timeout has occurred. If
* the timeout has not occurred, it is updated to reflect the number of
* reamaining ticks.
*
* @return If timeout has occurred, pdTRUE is returned. Otherwise pdFALSE is
* returned and pxTicksToWait is updated to reflect the number of remaining
* ticks.
*
* @see https://www.freertos.org/xTaskCheckForTimeOut.html
*
* Example Usage:
*
* // 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;
* }
*/
BaseType_t xTaskCheckForTimeOut( TimeOut_t * const pxTimeOut, TickType_t * const pxTicksToWait ) PRIVILEGED_FUNCTION;
/*
* Shortcut used by the queue implementation to prevent unnecessary call to
* taskYIELD();

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