A version of xTimerStop() that can be called from an interrupt service
The handle of the timer being stopped.
The timer service/daemon task spends most
of its time in the Blocked state, waiting for messages to arrive on the timer
command queue. Calling xTimerStopFromISR() writes a message to the timer
command queue, so has the potential to transition the timer service/daemon
task out of the Blocked state. If calling xTimerStopFromISR() causes the
timer service/daemon task to leave the Blocked state, and the timer service/
daemon task has a priority equal to or greater than the currently executing
task (the task that was interrupted), then *pxHigherPriorityTaskWoken will
get set to pdTRUE internally within the xTimerStopFromISR() function. If
xTimerStopFromISR() sets this value to pdTRUE, then a context switch should
be performed before the interrupt exits.
pdFAIL will be returned if the stop command could not be sent to
the timer command queue. pdPASS will be returned if the command was
successfully sent to the timer command queue. When the command is actually
processed will depend on the priority of the timer service/daemon task
relative to other tasks in the system. The timer service/daemon
task priority is set by the configTIMER_TASK_PRIORITY configuration constant.
/* This scenario assumes xTimer has already been created and started. When
an interrupt occurs, the timer should be simply stopped. */
/* The interrupt service routine that stops the timer. */
void vAnExampleInterruptServiceRoutine( void )
BaseType_t xHigherPriorityTaskWoken = pdFALSE;
/* The interrupt has occurred - simply stop the timer.
xHigherPriorityTaskWoken was set to pdFALSE where it was defined
(within this function). As this is an interrupt service routine, only
FreeRTOS API functions that end in "FromISR" can be used. */
if( xTimerStopFromISR( xTimer, &xHigherPriorityTaskWoken ) != pdPASS )
/* The stop command was not executed successfully. Take appropriate
action here. */
/* If xHigherPriorityTaskWoken equals pdTRUE, then a context switch
should be performed. The syntax required to perform a context switch
from inside an ISR varies from port to port, and from compiler to
compiler. Inspect the demos for the port you are using to find the
actual syntax required. */
if( xHigherPriorityTaskWoken != pdFALSE )
/* Call the interrupt safe yield function here (actual function
depends on the FreeRTOS port being used). */
Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.