Merge branch 'freertos'

1 files changed, 936 insertions, 0 deletions

diff --git a/libraries/FreeRTOS/utility/timers.h b/libraries/FreeRTOS/utility/timers.h
new file mode 100755
index 0000000..f1bcb0d
--- /dev/null
+++ b/libraries/FreeRTOS/utility/timers.h
@@ -0,0 +1,936 @@
+/*
+    FreeRTOS V7.0.1 - Copyright (C) 2011 Real Time Engineers Ltd.
+	
+
+	FreeRTOS supports many tools and architectures. V7.0.0 is sponsored by:
+	Atollic AB - Atollic provides professional embedded systems development 
+	tools for C/C++ development, code analysis and test automation.  
+	See http://www.atollic.com
+	
+
+    ***************************************************************************
+     *                                                                       *
+     *    FreeRTOS tutorial books are available in pdf and paperback.        *
+     *    Complete, revised, and edited pdf reference manuals are also       *
+     *    available.                                                         *
+     *                                                                       *
+     *    Purchasing FreeRTOS documentation will not only help you, by       *
+     *    ensuring you get running as quickly as possible and with an        *
+     *    in-depth knowledge of how to use FreeRTOS, it will also help       *
+     *    the FreeRTOS project to continue with its mission of providing     *
+     *    professional grade, cross platform, de facto standard solutions    *
+     *    for microcontrollers - completely free of charge!                  *
+     *                                                                       *
+     *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
+     *                                                                       *
+     *    Thank you for using FreeRTOS, and thank you for your support!      *
+     *                                                                       *
+    ***************************************************************************
+
+
+    This file is part of the FreeRTOS distribution.
+
+    FreeRTOS is free software; you can redistribute it and/or modify it under
+    the terms of the GNU General Public License (version 2) as published by the
+    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
+    >>>NOTE<<< The modification to the GPL is included to allow you to
+    distribute a combined work that includes FreeRTOS without being obliged to
+    provide the source code for proprietary components outside of the FreeRTOS
+    kernel.  FreeRTOS is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+    more details. You should have received a copy of the GNU General Public
+    License and the FreeRTOS license exception along with FreeRTOS; if not it
+    can be viewed here: http://www.freertos.org/a00114.html and also obtained
+    by writing to Richard Barry, contact details for whom are available on the
+    FreeRTOS WEB site.
+
+    1 tab == 4 spaces!
+
+    http://www.FreeRTOS.org - Documentation, latest information, license and
+    contact details.
+
+    http://www.SafeRTOS.com - A version that is certified for use in safety
+    critical systems.
+
+    http://www.OpenRTOS.com - Commercial support, development, porting,
+    licensing and training services.
+*/
+
+
+#ifndef TIMERS_H
+#define TIMERS_H
+
+#ifndef INC_FREERTOS_H
+	#error "include FreeRTOS.h must appear in source files before include timers.h"
+#endif
+
+#include "portable.h"
+#include "list.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* IDs for commands that can be sent/received on the timer queue.  These are to
+be used solely through the macros that make up the public software timer API,
+as defined below. */
+#define tmrCOMMAND_START					0
+#define tmrCOMMAND_STOP						1
+#define tmrCOMMAND_CHANGE_PERIOD			2
+#define tmrCOMMAND_DELETE					3
+
+/*-----------------------------------------------------------
+ * MACROS AND DEFINITIONS
+ *----------------------------------------------------------*/
+
+ /**
+ * Type by which software timers are referenced.  For example, a call to
+ * xTimerCreate() returns an xTimerHandle variable that can then be used to
+ * reference the subject timer in calls to other software timer API functions
+ * (for example, xTimerStart(), xTimerReset(), etc.).
+ */
+typedef void * xTimerHandle;
+
+/* Define the prototype to which timer callback functions must conform. */
+typedef void (*tmrTIMER_CALLBACK)( xTimerHandle xTimer );
+
+/**
+ * xTimerHandle xTimerCreate( 	const signed char *pcTimerName,
+ * 								portTickType xTimerPeriod,
+ * 								unsigned portBASE_TYPE uxAutoReload,
+ * 								void * pvTimerID,
+ * 								tmrTIMER_CALLBACK pxCallbackFunction );
+ *
+ * Creates a new software timer instance.  This allocates the storage required
+ * by the new timer, initialises the new timers internal state, and returns a
+ * handle by which the new timer can be referenced.
+ *
+ * Timers are created in the dormant state.  The xTimerStart(), xTimerReset(),
+ * xTimerStartFromISR(), xTimerResetFromISR(), xTimerChangePeriod() and
+ * xTimerChangePeriodFromISR() API functions can all be used to transition a timer into the
+ * active state.
+ *
+ * @param pcTimerName A text name that is assigned to the timer.  This is done
+ * purely to assist debugging.  The kernel itself only ever references a timer by
+ * its handle, and never by its name.
+ *
+ * @param xTimerPeriod The timer period.  The time is defined in tick periods so
+ * the constant portTICK_RATE_MS can be used to convert a time that has been
+ * specified in milliseconds.  For example, if the timer must expire after 100
+ * ticks, then xTimerPeriod should be set to 100.  Alternatively, if the timer
+ * must expire after 500ms, then xPeriod can be set to ( 500 / portTICK_RATE_MS )
+ * provided configTICK_RATE_HZ is less than or equal to 1000.
+ *
+ * @param uxAutoReload If uxAutoReload is set to pdTRUE then the timer will
+ * expire repeatedly with a frequency set by the xTimerPeriod parameter.  If
+ * uxAutoReload is set to pdFALSE then the timer will be a one-shot timer and
+ * enter the dormant state after it expires.
+ *
+ * @param pvTimerID An identifier that is assigned to the timer being created.
+ * Typically this would be used in the timer callback function to identify which
+ * timer expired when the same callback function is assigned to more than one
+ * timer.
+ *
+ * @param pxCallbackFunction The function to call when the timer expires.
+ * Callback functions must have the prototype defined by tmrTIMER_CALLBACK,
+ * which is	"void vCallbackFunction( xTIMER *xTimer );".
+ *
+ * @return If the timer is successfully create then a handle to the newly
+ * created timer is returned.  If the timer cannot be created (because either
+ * there is insufficient FreeRTOS heap remaining to allocate the timer
+ * structures, or the timer period was set to 0) then 0 is returned.
+ *
+ * Example usage:
+ *
+ *
+ * #define NUM_TIMERS 5
+ *
+ * // An array to hold handles to the created timers.
+ * xTimerHandle xTimers[ NUM_TIMERS ];
+ *
+ * // An array to hold a count of the number of times each timer expires.
+ * long lExpireCounters[ NUM_TIMERS ] = { 0 };
+ *
+ * // Define a callback function that will be used by multiple timer instances.
+ * // The callback function does nothing but count the number of times the
+ * // associated timer expires, and stop the timer once the timer has expired
+ * // 10 times.
+ * void vTimerCallback( xTIMER *pxTimer )
+ * {
+ * long lArrayIndex;
+ * const long xMaxExpiryCountBeforeStopping = 10;
+ *
+ * 	   // Optionally do something if the pxTimer parameter is NULL.
+ * 	   configASSERT( pxTimer );
+ * 	
+ *     // Which timer expired?
+ *     lArrayIndex = ( long ) pvTimerGetTimerID( pxTimer );
+ *
+ *     // Increment the number of times that pxTimer has expired.
+ *     lExpireCounters[ lArrayIndex ] += 1;
+ *
+ *     // If the timer has expired 10 times then stop it from running.
+ *     if( lExpireCounters[ lArrayIndex ] == xMaxExpiryCountBeforeStopping )
+ *     {
+ *         // Do not use a block time if calling a timer API function from a
+ *         // timer callback function, as doing so could cause a deadlock!
+ *         xTimerStop( pxTimer, 0 );
+ *     }
+ * }
+ *
+ * void main( void )
+ * {
+ * long x;
+ *
+ *     // Create then start some timers.  Starting the timers before the scheduler
+ *     // has been started means the timers will start running immediately that
+ *     // the scheduler starts.
+ *     for( x = 0; x < NUM_TIMERS; x++ )
+ *     {
+ *         xTimers[ x ] = xTimerCreate(     "Timer",         // Just a text name, not used by the kernel.
+ *                                         ( 100 * x ),     // The timer period in ticks.
+ *                                         pdTRUE,         // The timers will auto-reload themselves when they expire.
+ *                                         ( void * ) x,     // Assign each timer a unique id equal to its array index.
+ *                                         vTimerCallback     // Each timer calls the same callback when it expires.
+ *                                     );
+ *
+ *         if( xTimers[ x ] == NULL )
+ *         {
+ *             // The timer was not created.
+ *         }
+ *         else
+ *         {
+ *             // Start the timer.  No block time is specified, and even if one was
+ *             // it would be ignored because the scheduler has not yet been
+ *             // started.
+ *             if( xTimerStart( xTimers[ x ], 0 ) != pdPASS )
+ *             {
+ *                 // The timer could not be set into the Active state.
+ *             }
+ *         }
+ *     }
+ *
+ *     // ...
+ *     // Create tasks here.
+ *     // ...
+ *
+ *     // Starting the scheduler will start the timers running as they have already
+ *     // been set into the active state.
+ *     xTaskStartScheduler();
+ *
+ *     // Should not reach here.
+ *     for( ;; );
+ * }
+ */
+xTimerHandle xTimerCreate( const signed char *pcTimerName, portTickType xTimerPeriodInTicks, unsigned portBASE_TYPE uxAutoReload, void * pvTimerID, tmrTIMER_CALLBACK pxCallbackFunction ) PRIVILEGED_FUNCTION;
+
+/**
+ * void *pvTimerGetTimerID( xTimerHandle xTimer );
+ *
+ * Returns the ID assigned to the timer.
+ *
+ * IDs are assigned to timers using the pvTimerID parameter of the call to
+ * xTimerCreated() that was used to create the timer.
+ *
+ * If the same callback function is assigned to multiple timers then the timer
+ * ID can be used within the callback function to identify which timer actually
+ * expired.
+ *
+ * @param xTimer The timer being queried.
+ *
+ * @return The ID assigned to the timer being queried.
+ *
+ * Example usage:
+ *
+ * See the xTimerCreate() API function example usage scenario.
+ */
+void *pvTimerGetTimerID( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
+
+/**
+ * portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer );
+ *
+ * Queries a timer to see if it is active or dormant.
+ *
+ * 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.
+ *
+ * Timers are created in the dormant state.  The xTimerStart(), xTimerReset(),
+ * xTimerStartFromISR(), xTimerResetFromISR(), xTimerChangePeriod() and
+ * xTimerChangePeriodFromISR() API functions can all be used to transition a timer into the
+ * active state.
+ *
+ * @param xTimer The timer being queried.
+ *
+ * @return pdFALSE will be returned if the timer is dormant.  A value other than
+ * pdFALSE will be returned if the timer is active.
+ *
+ * Example usage:
+ *
+ * // This function assumes xTimer has already been created.
+ * void vAFunction( xTimerHandle xTimer )
+ * {
+ *     if( xTimerIsTimerActive( xTimer ) != pdFALSE ) // or more simply and equivalently "if( xTimerIsTimerActive( xTimer ) )"
+ *     {
+ *         // xTimer is active, do something.
+ *     }
+ *     else
+ *     {
+ *         // xTimer is not active, do something else.
+ *     }
+ * }
+ */
+portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
+
+/**
+ * portBASE_TYPE xTimerStart( xTimerHandle xTimer, portTickType xBlockTime );
+ *
+ * Timer functionality is provided by a timer service/daemon task.  Many of the
+ * public FreeRTOS timer API functions send commands to the timer service task
+ * though a queue called the timer command queue.  The timer command queue is
+ * private to the kernel itself and is not directly accessible to application
+ * code.  The length of the timer command queue is set by the
+ * configTIMER_QUEUE_LENGTH configuration constant.
+ *
+ * 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 equivalent functionality
+ * to the xTimerReset() API function.
+ *
+ * Starting 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
+ * associated with the timer will get called 'n' ticks after xTimerStart() was
+ * called, where 'n' is the timers defined period.
+ *
+ * It is valid to call xTimerStart() before the scheduler has been started, but
+ * when this is done the timer will not actually start until the scheduler is
+ * started, and the timers expiry time will be relative to when the scheduler is
+ * started, not relative to when xTimerStart() was called.
+ *
+ * The configUSE_TIMERS configuration constant must be set to 1 for xTimerStart()
+ * to be available.
+ *
+ * @param xTimer The handle of the timer being started/restarted.
+ *
+ * @param xBlockTime Specifies the time, in ticks, that the calling task should
+ * be held in the Blocked state to wait for the start command to be successfully
+ * sent to the timer command queue, should the queue already be full when
+ * xTimerStart() was called.  xBlockTime is ignored if xTimerStart() is called
+ * before the scheduler is started.
+ *
+ * @return pdFAIL will be returned if the start command could not be sent to
+ * the timer command queue even after xBlockTime ticks had passed.  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, 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:
+ *
+ * See the xTimerCreate() API function example usage scenario.
+ *
+ */
+#define xTimerStart( xTimer, xBlockTime ) xTimerGenericCommand( ( xTimer ), tmrCOMMAND_START, ( xTaskGetTickCount() ), NULL, ( xBlockTime ) )
+
+/**
+ * portBASE_TYPE xTimerStop( xTimerHandle xTimer, portTickType xBlockTime );
+ *
+ * Timer functionality is provided by a timer service/daemon task.  Many of the
+ * public FreeRTOS timer API functions send commands to the timer service task
+ * though a queue called the timer command queue.  The timer command queue is
+ * private to the kernel itself and is not directly accessible to application
+ * code.  The length of the timer command queue is set by the
+ * configTIMER_QUEUE_LENGTH configuration constant.
+ *
+ * xTimerStop() stops a timer that was previously started using either of the
+ * The xTimerStart(), xTimerReset(), xTimerStartFromISR(), xTimerResetFromISR(),
+ * xTimerChangePeriod() or xTimerChangePeriodFromISR() API functions.
+ *
+ * Stopping a timer ensures the timer is not in the active state.
+ *
+ * The configUSE_TIMERS configuration constant must be set to 1 for xTimerStop()
+ * to be available.
+ *
+ * @param xTimer The handle of the timer being stopped.
+ *
+ * @param xBlockTime Specifies the time, in ticks, that the calling task should
+ * be held in the Blocked state to wait for the stop command to be successfully
+ * sent to the timer command queue, should the queue already be full when
+ * xTimerStop() was called.  xBlockTime is ignored if xTimerStop() is called
+ * before the scheduler is started.
+ *
+ * @return pdFAIL will be returned if the stop command could not be sent to
+ * the timer command queue even after xBlockTime ticks had passed.  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.
+ *
+ * Example usage:
+ *
+ * See the xTimerCreate() API function example usage scenario.
+ *
+ */
+#define xTimerStop( xTimer, xBlockTime ) xTimerGenericCommand( ( xTimer ), tmrCOMMAND_STOP, 0U, NULL, ( xBlockTime ) )
+
+/**
+ * portBASE_TYPE xTimerChangePeriod( 	xTimerHandle xTimer,
+ *										portTickType xNewPeriod,
+ *										portTickType xBlockTime );
+ *
+ * Timer functionality is provided by a timer service/daemon task.  Many of the
+ * public FreeRTOS timer API functions send commands to the timer service task
+ * though a queue called the timer command queue.  The timer command queue is
+ * private to the kernel itself and is not directly accessible to application
+ * code.  The length of the timer command queue is set by the
+ * configTIMER_QUEUE_LENGTH configuration constant.
+ *
+ * xTimerChangePeriod() changes the period of a timer that was previously
+ * created using the xTimerCreate() API function.
+ *
+ * xTimerChangePeriod() can be called to change the period of an active or
+ * dormant state timer.
+ *
+ * The configUSE_TIMERS configuration constant must be set to 1 for
+ * xTimerChangePeriod() to be available.
+ *
+ * @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
+ * that has been specified in milliseconds.  For example, if the timer must
+ * expire after 100 ticks, then xNewPeriod should be set to 100.  Alternatively,
+ * if the timer must expire after 500ms, then xNewPeriod can be set to
+ * ( 500 / portTICK_RATE_MS ) provided configTICK_RATE_HZ is less than
+ * or equal to 1000.
+ *
+ * @param xBlockTime Specifies the time, in ticks, that the calling task should
+ * be held in the Blocked state to wait for the change period command to be
+ * successfully sent to the timer command queue, should the queue already be
+ * full when xTimerChangePeriod() was called.  xBlockTime is ignored if
+ * xTimerChangePeriod() is called before the scheduler is started.
+ *
+ * @return pdFAIL will be returned if the change period command could not be
+ * sent to the timer command queue even after xBlockTime ticks had passed.
+ * 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.
+ *
+ * Example usage:
+ *
+ * // This function assumes xTimer has already been created.  If the timer
+ * // referenced by xTimer is already active when it is called, then the timer
+ * // is deleted.  If the timer referenced by xTimer is not active when it is
+ * // called, then the period of the timer is set to 500ms and the timer is
+ * // started.
+ * void vAFunction( xTimerHandle xTimer )
+ * {
+ *     if( xTimerIsTimerActive( xTimer ) != pdFALSE ) // or more simply and equivalently "if( xTimerIsTimerActive( xTimer ) )"
+ *     {
+ *         // xTimer is already active - delete it.
+ *         xTimerDelete( xTimer );
+ *     }
+ *     else
+ *     {
+ *         // xTimer is not active, change its period to 500ms.  This will also
+ *         // cause the timer to start.  Block for a maximum of 100 ticks if the
+ *         // change period command cannot immediately be sent to the timer
+ *         // command queue.
+ *         if( xTimerChangePeriod( xTimer, 500 / portTICK_RATE_MS, 100 ) == pdPASS )
+ *         {
+ *             // The command was successfully sent.
+ *         }
+ *         else
+ *         {
+ *             // The command could not be sent, even after waiting for 100 ticks
+ *             // to pass.  Take appropriate action here.
+ *         }
+ *     }
+ * }
+ */
+ #define xTimerChangePeriod( xTimer, xNewPeriod, xBlockTime ) xTimerGenericCommand( ( xTimer ), tmrCOMMAND_CHANGE_PERIOD, ( xNewPeriod ), NULL, ( xBlockTime ) )
+
+/**
+ * portBASE_TYPE xTimerDelete( xTimerHandle xTimer, portTickType xBlockTime );
+ *
+ * Timer functionality is provided by a timer service/daemon task.  Many of the
+ * public FreeRTOS timer API functions send commands to the timer service task
+ * though a queue called the timer command queue.  The timer command queue is
+ * private to the kernel itself and is not directly accessible to application
+ * code.  The length of the timer command queue is set by the
+ * configTIMER_QUEUE_LENGTH configuration constant.
+ *
+ * xTimerDelete() deletes a timer that was previously created using the
+ * xTimerCreate() API function.
+ *
+ * The configUSE_TIMERS configuration constant must be set to 1 for
+ * xTimerDelete() to be available.
+ *
+ * @param xTimer The handle of the timer being deleted.
+ *
+ * @param xBlockTime Specifies the time, in ticks, that the calling task should
+ * be held in the Blocked state to wait for the delete command to be
+ * successfully sent to the timer command queue, should the queue already be
+ * full when xTimerDelete() was called.  xBlockTime is ignored if xTimerDelete()
+ * is called before the scheduler is started.
+ *
+ * @return pdFAIL will be returned if the delete command could not be sent to
+ * the timer command queue even after xBlockTime ticks had passed.  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.
+ *
+ * Example usage:
+ *
+ * See the xTimerChangePeriod() API function example usage scenario.
+ */
+#define xTimerDelete( xTimer, xBlockTime ) xTimerGenericCommand( ( xTimer ), tmrCOMMAND_DELETE, 0U, NULL, ( xBlockTime ) )
+
+/**
+ * portBASE_TYPE xTimerReset( xTimerHandle xTimer, portTickType xBlockTime );
+ *
+ * Timer functionality is provided by a timer service/daemon task.  Many of the
+ * public FreeRTOS timer API functions send commands to the timer service task
+ * though a queue called the timer command queue.  The timer command queue is
+ * private to the kernel itself and is not directly accessible to application
+ * code.  The length of the timer command queue is set by the
+ * configTIMER_QUEUE_LENGTH configuration constant.
+ *
+ * xTimerReset() re-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 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
+ * 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
+ * associated with the timer will get called 'n' ticks after xTimerReset() was
+ * called, where 'n' is the timers defined period.
+ *
+ * It is valid to call xTimerReset() before the scheduler has been started, but
+ * when this is done the timer will not actually start until the scheduler is
+ * started, and the timers expiry time will be relative to when the scheduler is
+ * started, not relative to when xTimerReset() was called.
+ *
+ * The configUSE_TIMERS configuration constant must be set to 1 for xTimerReset()
+ * to be available.
+ *
+ * @param xTimer The handle of the timer being reset/started/restarted.
+ *
+ * @param xBlockTime Specifies the time, in ticks, that the calling task should
+ * be held in the Blocked state to wait for the reset command to be successfully
+ * sent to the timer command queue, should the queue already be full when
+ * xTimerReset() was called.  xBlockTime is ignored if xTimerReset() is called
+ * before the scheduler is started.
+ *
+ * @return pdFAIL will be returned if the reset command could not be sent to
+ * the timer command queue even after xBlockTime ticks had passed.  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, 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:
+ *
+ * // 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;
+ *
+ * // 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 event handler.
+ * void vKeyPressEventHandler( char cKey )
+ * {
+ *     // 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( xTimerReset( xBacklightTimer, 100 ) != pdPASS )
+ *     {
+ *         // The reset command was not executed successfully.  Take appropriate
+ *         // action here.
+ *     }
+ *
+ *     // Perform the rest of the key processing here.
+ * }
+ *
+ * void main( void )
+ * {
+ * long x;
+ *
+ *     // Create then start the one-shot timer that is responsible for turning
+ *     // 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 back-light off.
+ *                                   );
+ *
+ *     if( xBacklightTimer == NULL )
+ *     {
+ *         // The timer was not created.
+ *     }
+ *     else
+ *     {
+ *         // Start the timer.  No block time is specified, and even if one was
+ *         // it would be ignored because the scheduler has not yet been
+ *         // started.
+ *         if( xTimerStart( xBacklightTimer, 0 ) != pdPASS )
+ *         {
+ *             // The timer could not be set into the Active state.
+ *         }
+ *     }
+ *
+ *     // ...
+ *     // Create tasks here.
+ *     // ...
+ *
+ *     // Starting the scheduler will start the timer running as it has already
+ *     // been set into the active state.
+ *     xTaskStartScheduler();
+ *
+ *     // Should not reach here.
+ *     for( ;; );
+ * }
+ */
+#define xTimerReset( xTimer, xBlockTime ) xTimerGenericCommand( ( xTimer ), tmrCOMMAND_START, ( xTaskGetTickCount() ), NULL, ( xBlockTime ) )
+
+/**
+ * portBASE_TYPE xTimerStartFromISR( 	xTimerHandle xTimer,
+ *										portBASE_TYPE *pxHigherPriorityTaskWoken );
+ *
+ * A version of xTimerStart() that can be called from an interrupt service
+ * routine.
+ *
+ * @param xTimer The handle of the timer being started/restarted.
+ *
+ * @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 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, although the timers expiry time is
+ * relative to when xTimerStartFromISR() 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 ), 0U )
+
+/**
+ * portBASE_TYPE xTimerStopFromISR( 	xTimerHandle xTimer,
+ *										portBASE_TYPE *pxHigherPriorityTaskWoken );
+ *
+ * A version of xTimerStop() that can be called from an interrupt service
+ * routine.
+ *
+ * @param xTimer The handle of the timer being stopped.
+ *
+ * @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 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.
+ *
+ * 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 ), 0U )
+
+/**
+ * portBASE_TYPE xTimerChangePeriodFromISR( xTimerHandle xTimer,
+ *											portTickType xNewPeriod,
+ *											portBASE_TYPE *pxHigherPriorityTaskWoken );
+ *
+ * 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 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
+ * that has been specified in milliseconds.  For example, if the timer must
+ * expire after 100 ticks, then xNewPeriod should be set to 100.  Alternatively,
+ * if the timer must expire after 500ms, then xNewPeriod can be set to
+ * ( 500 / portTICK_RATE_MS ) provided configTICK_RATE_HZ is less than
+ * or equal to 1000.
+ *
+ * @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 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.
+ *
+ * Example usage:
+ *
+ * // This scenario assumes xTimer has already been created and started.  When
+ * // an interrupt occurs, the period of xTimer should be changed to 500ms.
+ *
+ * // 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 ), 0U )
+
+/**
+ * portBASE_TYPE xTimerResetFromISR( 	xTimerHandle xTimer,
+ *										portBASE_TYPE *pxHigherPriorityTaskWoken );
+ *
+ * A version of xTimerReset() that can be called from an interrupt service
+ * routine.
+ *
+ * @param xTimer The handle of the timer that is to be started, reset, or
+ * restarted.
+ *
+ * @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 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, although the timers expiry time is
+ * relative to when xTimerResetFromISR() 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 ), 0U )
+
+/*
+ * Functions beyond this part are not part of the public API and are intended
+ * for use by the kernel only.
+ */
+portBASE_TYPE xTimerCreateTimerTask( void ) PRIVILEGED_FUNCTION;
+portBASE_TYPE xTimerGenericCommand( xTimerHandle xTimer, portBASE_TYPE xCommandID, portTickType xOptionalValue, portBASE_TYPE *pxHigherPriorityTaskWoken, portTickType xBlockTime ) PRIVILEGED_FUNCTION;
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* TIMERS_H */
+
+
+