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Continue work on timers module documentation.

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pull/4/head
Richard Barry 14 years ago
parent 0e133bc0fc
commit 8a3fa98a2f
1 changed files with 264 additions and 27 deletions
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Source/include/timers.h
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@ -244,7 +244,7 @@ void *pvTimerGetTimerID( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
*
* Queries a timer to see if it is active or dormant.
*
* A timer will be ormant if:
* A timer will be dormant if:
* 1) It has been created but not started, or
* 2) It is an expired on-shot timer that has not been restarted.
*
@ -286,7 +286,7 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
*
* xTimerStart() starts a timer that was previously created using the
* xTimerCreate() API function. If the timer had already been started and was
* already in the active state, then xTimerStart() has equaivalent functionality
* already in the active state, then xTimerStart() has equivalent functionality
* to the xTimerReset() API function.
*
* Starting a timer ensures the timer is in the active state. If the timer
@ -389,7 +389,7 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* The configUSE_TIMERS configuration constant must be set to 1 for
* xTimerChangePeriod() to be available.
*
* @param xTimer The handle of the timer being stopped.
* @param xTimer The handle of the timer that is having its period changed.
*
* @param xNewPeriod The new period for xTimer. Timer periods are specified in
* tick periods, so the constant portTICK_RATE_MS can be used to convert a time
@ -500,7 +500,7 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* already in the active state, then xTimerReset() will cause the timer to
* re-evaluate its expiry time so that it is relative to when xTimerReset() was
* called. If the timer was in the dormant state then xTimerReset() has
* equaivalent functionality to the xTimerStart() API function.
* equivalent functionality to the xTimerStart() API function.
*
* Resetting a timer ensures the timer is in the active state. If the timer
* is not stopped, deleted, or reset in the mean time, the callback function
@ -534,10 +534,9 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
*
* Example usage:
*
* // This scenario assumes xTimer has already been created. When a key is
* // pressed, an LCD backlight is switched on. If 5 seconds pass without a key
* // being pressed, then the LCD backlight is switched off. In this case, the
* // timer is a one-shot timer.
* // When a key is pressed, an LCD back-light is switched on. If 5 seconds pass
* // without a key being pressed, then the LCD back-light is switched off. In
* // this case, the timer is a one-shot timer.
*
* xTimerHandle xBacklightTimer = NULL;
*
@ -546,19 +545,19 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* void vBacklightTimerCallback( xTIMER *pxTimer )
* {
* // The timer expired, therefore 5 seconds must have passed since a key
* // was pressed. Switch off the LCD backlight.
* // was pressed. Switch off the LCD back-light.
* vSetBacklightState( BACKLIGHT_OFF );
* }
*
* // The key press event handler.
* void vKeyPressEventHandler( char cKey )
* {
* // Ensure the LCD backlight is on, then reset the timer that is
* // responsible for turning the backlight off after 5 seconds of
* // Ensure the LCD back-light is on, then reset the timer that is
* // responsible for turning the back-light off after 5 seconds of
* // key inactivity. Wait 10 ticks for the command to be successfully sent
* // if it cannot be sent immediately.
* vSetBacklightState( BACKLIGHT_ON );
* if( vTimerReset( xBacklightTimer, 100 ) != pdPASS )
* if( xTimerReset( xBacklightTimer, 100 ) != pdPASS )
* {
* // The reset command was not executed successfully. Take appropriate
* // action here.
@ -572,12 +571,12 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* long x;
*
* // Create then start the one-shot timer that is responsible for turning
* // the backlight off if no keys are pressed within a 5 second period.
* // the back-light off if no keys are pressed within a 5 second period.
* xBacklightTimer = xTimerCreate( "BacklightTimer", // Just a text name, not used by the kernel.
* ( 5000 / portTICK_RATE_MS), // The timer period in ticks.
* pdFALSE, // The timer is a one-shot timer.
* 0, // The id is not used by the callback so can take any value.
* vBacklightTimerCallback // The callback function that switches the LCD backlight off.
* vBacklightTimerCallback // The callback function that switches the LCD back-light off.
* );
*
* if( xBacklightTimer == NULL )
@ -613,13 +612,83 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* portBASE_TYPE xTimerStartFromISR( xTimerHandle xTimer,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
* A version of xTimerStart() that can be called from an interrupt service
* routine.
*
* @param xTimer
* @param xTimer The handle of the timer being started/restarted.
*
* @return
* @param pxHigherPriorityTaskWoken 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 xTimerStartFromISR() 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 xTimerStartFromISR() 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 xTimerStartFromISR() function. If
* xTimerStartFromISR() sets this value to pdTRUE then a context switch should
* be performed before the interrupt exits.
*
* @return pdFAIL will be returned if the start command could not be sent to
* the timer command queue. pdPASS will be returned if the command was
* successfully send 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, although the timers expiry time is
* relative to when xTimerStart() is actually called. The timer service/daemon
* task priority is set by the configTIMER_TASK_PRIORITY configuration constant.
*
* Example usage:
*
* // This scenario assumes xBacklightTimer has already been created. When a
* // key is pressed, an LCD back-light is switched on. If 5 seconds pass
* // without a key being pressed, then the LCD back-light is switched off. In
* // this case, the timer is a one-shot timer, and unlike the example given for
* // the xTimerReset() function, the key press event handler is an interrupt
* // service routine.
*
* // The callback function assigned to the one-shot timer. In this case the
* // parameter is not used.
* void vBacklightTimerCallback( xTIMER *pxTimer )
* {
* // The timer expired, therefore 5 seconds must have passed since a key
* // was pressed. Switch off the LCD back-light.
* vSetBacklightState( BACKLIGHT_OFF );
* }
*
* // The key press interrupt service routine.
* void vKeyPressEventInterruptHandler( void )
* {
* portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
*
* // Ensure the LCD back-light is on, then restart the timer that is
* // responsible for turning the back-light off after 5 seconds of
* // key inactivity. This is an interrupt service routine so can only
* // call FreeRTOS API functions that end in "FromISR".
* vSetBacklightState( BACKLIGHT_ON );
*
* // xTimerStartFromISR() or xTimerResetFromISR() could be called here
* // as both cause the timer to re-calculate its expiry time.
* // xHigherPriorityTaskWoken was initialised to pdFALSE when it was
* // declared (in this function).
* if( xTimerStartFromISR( xBacklightTimer, &xHigherPriorityTaskWoken ) != pdPASS )
* {
* // The start command was not executed successfully. Take appropriate
* // action here.
* }
*
* // Perform the rest of the key processing 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.
* }
* }
*/
#define xTimerStartFromISR( xTimer, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_START, xTaskGetTickCountFromISR(), pxHigherPriorityTaskWoken, 0 )
@ -627,13 +696,61 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* portBASE_TYPE xTimerStopFromISR( xTimerHandle xTimer,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
* A version of xTimerStop() that can be called from an interrupt service
* routine.
*
* @param xTimer
* @param xTimer The handle of the timer being stopped.
*
* @return
* @param pxHigherPriorityTaskWoken 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.
*
* @return 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 send 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.
*
* Example usage:
*
* // 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 )
* {
* portBASE_TYPE 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.
* }
* }
*/
#define xTimerStopFromISR( xTimer, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_STOP, 0, pxHigherPriorityTaskWoken, 0 )
@ -642,13 +759,62 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* portTickType xNewPeriod,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
* A version of xTimerChangePeriod() that can be called from an interrupt
* service routine.
*
* @param xTimer The handle of the timer that is having its period changed.
*
* @param pxHigherPriorityTaskWoken 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 xTimerChangePeriodFromISR() 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 xTimerChangePeriodFromISR()
* 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
* xTimerChangePeriodFromISR() function. If xTimerChangePeriodFromISR() sets
* this value to pdTRUE then a context switch should be performed before the
* interrupt exits.
*
* @return pdFAIL will be returned if the command to change the timers period
* could not be sent to the timer command queue. pdPASS will be returned if the
* command was successfully send 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.
*
* @param xTimer
* Example usage:
*
* @return
* // This scenario assumes xTimer has already been created and started. When
* // an interrupt occurs, the period of xTimer should be changed to 500ms.
*
* Example usage:
* // The interrupt service routine that changes the period of xTimer.
* void vAnExampleInterruptServiceRoutine( void )
* {
* portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
*
* // The interrupt has occurred - change the period of xTimer to 500ms.
* // 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( xTimerChangePeriodFromISR( xTimer, &xHigherPriorityTaskWoken ) != pdPASS )
* {
* // The command to change the timers period 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.
* }
* }
*/
#define xTimerChangePeriodFromISR( xTimer, xNewPeriod, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_CHANGE_PERIOD, xNewPeriod, pxHigherPriorityTaskWoken, 0 )
@ -656,13 +822,84 @@ portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
* portBASE_TYPE xTimerResetFromISR( xTimerHandle xTimer,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
* A version of xTimerReset() that can be called from an interrupt service
* routine.
*
* @param xTimer
* @param xTimer The handle of the timer that is to be started, reset, or
* restarted.
*
* @return
* @param pxHigherPriorityTaskWoken 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 xTimerResetFromISR() 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 xTimerResetFromISR() 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 xTimerResetFromISR() function. If
* xTimerResetFromISR() sets this value to pdTRUE then a context switch should
* be performed before the interrupt exits.
*
* @return pdFAIL will be returned if the reset command could not be sent to
* the timer command queue. pdPASS will be returned if the command was
* successfully send 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, although the timers expiry time is
* relative to when xTimerStart() is actually called. The timer service/daemon
* task priority is set by the configTIMER_TASK_PRIORITY configuration constant.
*
* Example usage:
*
* // This scenario assumes xBacklightTimer has already been created. When a
* // key is pressed, an LCD back-light is switched on. If 5 seconds pass
* // without a key being pressed, then the LCD back-light is switched off. In
* // this case, the timer is a one-shot timer, and unlike the example given for
* // the xTimerReset() function, the key press event handler is an interrupt
* // service routine.
*
* // The callback function assigned to the one-shot timer. In this case the
* // parameter is not used.
* void vBacklightTimerCallback( xTIMER *pxTimer )
* {
* // The timer expired, therefore 5 seconds must have passed since a key
* // was pressed. Switch off the LCD back-light.
* vSetBacklightState( BACKLIGHT_OFF );
* }
*
* // The key press interrupt service routine.
* void vKeyPressEventInterruptHandler( void )
* {
* portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
*
* // Ensure the LCD back-light is on, then reset the timer that is
* // responsible for turning the back-light off after 5 seconds of
* // key inactivity. This is an interrupt service routine so can only
* // call FreeRTOS API functions that end in "FromISR".
* vSetBacklightState( BACKLIGHT_ON );
*
* // xTimerStartFromISR() or xTimerResetFromISR() could be called here
* // as both cause the timer to re-calculate its expiry time.
* // xHigherPriorityTaskWoken was initialised to pdFALSE when it was
* // declared (in this function).
* if( xTimerResetFromISR( xBacklightTimer, &xHigherPriorityTaskWoken ) != pdPASS )
* {
* // The reset command was not executed successfully. Take appropriate
* // action here.
* }
*
* // Perform the rest of the key processing 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.
* }
* }
*/
#define xTimerResetFromISR( xTimer, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_START, xTaskGetTickCountFromISR(), pxHigherPriorityTaskWoken, 0 )

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