Timers

FreeRTOS/include/FreeRTOS.h

@@ -1159,6 +1159,12 @@ typedef struct xSTATIC_EVENT_GROUP
     struct rt_event event;
 } StaticEventGroup_t;
 
+typedef struct xSTATIC_TIMER
+{
+    struct rt_timer timer;
+    void * pvTimerID;
+} StaticTimer_t;
+
 /* *INDENT-OFF* */
 #ifdef __cplusplus
     }

FreeRTOS/include/FreeRTOSConfig.h

@@ -75,7 +75,6 @@ FreeRTOS/Source/tasks.c for limitations. */
 #define configMAX_CO_ROUTINE_PRIORITIES ( 2 )
 
 /* Software timer definitions. */
-#define configUSE_TIMERS                1
 #define configTIMER_TASK_PRIORITY       ( configMAX_PRIORITIES - 1 )
 #define configTIMER_QUEUE_LENGTH        5
 #define configTIMER_TASK_STACK_DEPTH    ( configMINIMAL_STACK_SIZE * 2 )
@@ -141,5 +140,6 @@ standard names. */
 #define configUSE_TASK_NOTIFICATIONS            1
 #define INCLUDE_eTaskGetState                   1
 #define configMAX_PRIORITIES                    ( 32 )
+#define configUSE_TIMERS                        1
 
 #endif /* FREERTOS_CONFIG_H */

FreeRTOS/include/timers.h

@@ -0,0 +1,1185 @@
+/*
+ * FreeRTOS Kernel V10.4.6
+ * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
+ */
+
+
+#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 "task.h"
+
+/* *INDENT-OFF* */
+#ifdef __cplusplus
+    extern "C" {
+#endif
+/* *INDENT-ON* */
+
+/*-----------------------------------------------------------
+* MACROS AND DEFINITIONS
+*----------------------------------------------------------*/
+
+/* 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.  The commands that are sent from interrupts must use the
+ * highest numbers as tmrFIRST_FROM_ISR_COMMAND is used to determine if the task
+ * or interrupt version of the queue send function should be used. */
+#define tmrCOMMAND_EXECUTE_CALLBACK_FROM_ISR    ( ( BaseType_t ) -2 )
+#define tmrCOMMAND_EXECUTE_CALLBACK             ( ( BaseType_t ) -1 )
+#define tmrCOMMAND_START_DONT_TRACE             ( ( BaseType_t ) 0 )
+#define tmrCOMMAND_START                        ( ( BaseType_t ) 1 )
+#define tmrCOMMAND_RESET                        ( ( BaseType_t ) 2 )
+#define tmrCOMMAND_STOP                         ( ( BaseType_t ) 3 )
+#define tmrCOMMAND_CHANGE_PERIOD                ( ( BaseType_t ) 4 )
+#define tmrCOMMAND_DELETE                       ( ( BaseType_t ) 5 )
+
+#define tmrFIRST_FROM_ISR_COMMAND               ( ( BaseType_t ) 6 )
+#define tmrCOMMAND_START_FROM_ISR               ( ( BaseType_t ) 6 )
+#define tmrCOMMAND_RESET_FROM_ISR               ( ( BaseType_t ) 7 )
+#define tmrCOMMAND_STOP_FROM_ISR                ( ( BaseType_t ) 8 )
+#define tmrCOMMAND_CHANGE_PERIOD_FROM_ISR       ( ( BaseType_t ) 9 )
+
+/**
+ * Type by which software timers are referenced.  For example, a call to
+ * xTimerCreate() returns an TimerHandle_t variable that can then be used to
+ * reference the subject timer in calls to other software timer API functions
+ * (for example, xTimerStart(), xTimerReset(), etc.).
+ */
+struct tmrTimerControl; /* The old naming convention is used to prevent breaking kernel aware debuggers. */
+typedef struct tmrTimerControl * TimerHandle_t;
+
+/*
+ * Defines the prototype to which timer callback functions must conform.
+ */
+typedef void (* TimerCallbackFunction_t)( TimerHandle_t xTimer );
+
+/**
+ * TimerHandle_t xTimerCreate(  const char * const pcTimerName,
+ *                              TickType_t xTimerPeriodInTicks,
+ *                              UBaseType_t uxAutoReload,
+ *                              void * pvTimerID,
+ *                              TimerCallbackFunction_t pxCallbackFunction );
+ *
+ * Creates a new software timer instance, and returns a handle by which the
+ * created software timer can be referenced.
+ *
+ * Internally, within the FreeRTOS implementation, software timers use a block
+ * of memory, in which the timer data structure is stored.  If a software timer
+ * is created using xTimerCreate() then the required memory is automatically
+ * dynamically allocated inside the xTimerCreate() function.  (see
+ * https://www.FreeRTOS.org/a00111.html).  If a software timer is created using
+ * xTimerCreateStatic() then the application writer must provide the memory that
+ * will get used by the software timer.  xTimerCreateStatic() therefore allows a
+ * software timer to be created without using any dynamic memory allocation.
+ *
+ * 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 xTimerPeriodInTicks The timer period.  The time is defined in tick
+ * periods so the constant portTICK_PERIOD_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 xTimerPeriodInTicks should be set to 100.
+ * Alternatively, if the timer must expire after 500ms, then xPeriod can be set
+ * to ( 500 / portTICK_PERIOD_MS ) provided configTICK_RATE_HZ is less than or
+ * equal to 1000.  Time timer period must be greater than 0.
+ *
+ * @param uxAutoReload If uxAutoReload is set to pdTRUE then the timer will
+ * expire repeatedly with a frequency set by the xTimerPeriodInTicks 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 TimerCallbackFunction_t,
+ * which is "void vCallbackFunction( TimerHandle_t xTimer );".
+ *
+ * @return If the timer is successfully created then a handle to the newly
+ * created timer is returned.  If the timer cannot be created because there is
+ * insufficient FreeRTOS heap remaining to allocate the timer
+ * structures then NULL is returned.
+ *
+ * Example usage:
+ * @verbatim
+ * #define NUM_TIMERS 5
+ *
+ * // An array to hold handles to the created timers.
+ * TimerHandle_t xTimers[ NUM_TIMERS ];
+ *
+ * // An array to hold a count of the number of times each timer expires.
+ * int32_t 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( TimerHandle_t pxTimer )
+ * {
+ * int32_t lArrayIndex;
+ * const int32_t xMaxExpiryCountBeforeStopping = 10;
+ *
+ *     // Optionally do something if the pxTimer parameter is NULL.
+ *     configASSERT( pxTimer );
+ *
+ *     // Which timer expired?
+ *     lArrayIndex = ( int32_t ) 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 )
+ * {
+ * int32_t 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.
+ *     vTaskStartScheduler();
+ *
+ *     // Should not reach here.
+ *     for( ;; );
+ * }
+ * @endverbatim
+ */
+#if ( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
+    TimerHandle_t xTimerCreate( const char * const pcTimerName, /*lint !e971 Unqualified char types are allowed for strings and single characters only. */
+                                const TickType_t xTimerPeriodInTicks,
+                                const UBaseType_t uxAutoReload,
+                                void * const pvTimerID,
+                                TimerCallbackFunction_t pxCallbackFunction );
+#endif
+
+/**
+ * TimerHandle_t xTimerCreateStatic(const char * const pcTimerName,
+ *                                  TickType_t xTimerPeriodInTicks,
+ *                                  UBaseType_t uxAutoReload,
+ *                                  void * pvTimerID,
+ *                                  TimerCallbackFunction_t pxCallbackFunction,
+ *                                  StaticTimer_t *pxTimerBuffer );
+ *
+ * Creates a new software timer instance, and returns a handle by which the
+ * created software timer can be referenced.
+ *
+ * Internally, within the FreeRTOS implementation, software timers use a block
+ * of memory, in which the timer data structure is stored.  If a software timer
+ * is created using xTimerCreate() then the required memory is automatically
+ * dynamically allocated inside the xTimerCreate() function.  (see
+ * https://www.FreeRTOS.org/a00111.html).  If a software timer is created using
+ * xTimerCreateStatic() then the application writer must provide the memory that
+ * will get used by the software timer.  xTimerCreateStatic() therefore allows a
+ * software timer to be created without using any dynamic memory allocation.
+ *
+ * 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 xTimerPeriodInTicks The timer period.  The time is defined in tick
+ * periods so the constant portTICK_PERIOD_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 xTimerPeriodInTicks should be set to 100.
+ * Alternatively, if the timer must expire after 500ms, then xPeriod can be set
+ * to ( 500 / portTICK_PERIOD_MS ) provided configTICK_RATE_HZ is less than or
+ * equal to 1000.  The timer period must be greater than 0.
+ *
+ * @param uxAutoReload If uxAutoReload is set to pdTRUE then the timer will
+ * expire repeatedly with a frequency set by the xTimerPeriodInTicks 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 TimerCallbackFunction_t,
+ * which is "void vCallbackFunction( TimerHandle_t xTimer );".
+ *
+ * @param pxTimerBuffer Must point to a variable of type StaticTimer_t, which
+ * will be then be used to hold the software timer's data structures, removing
+ * the need for the memory to be allocated dynamically.
+ *
+ * @return If the timer is created then a handle to the created timer is
+ * returned.  If pxTimerBuffer was NULL then NULL is returned.
+ *
+ * Example usage:
+ * @verbatim
+ *
+ * // The buffer used to hold the software timer's data structure.
+ * static StaticTimer_t xTimerBuffer;
+ *
+ * // A variable that will be incremented by the software timer's callback
+ * // function.
+ * UBaseType_t uxVariableToIncrement = 0;
+ *
+ * // A software timer callback function that increments a variable passed to
+ * // it when the software timer was created.  After the 5th increment the
+ * // callback function stops the software timer.
+ * static void prvTimerCallback( TimerHandle_t xExpiredTimer )
+ * {
+ * UBaseType_t *puxVariableToIncrement;
+ * BaseType_t xReturned;
+ *
+ *     // Obtain the address of the variable to increment from the timer ID.
+ *     puxVariableToIncrement = ( UBaseType_t * ) pvTimerGetTimerID( xExpiredTimer );
+ *
+ *     // Increment the variable to show the timer callback has executed.
+ *     ( *puxVariableToIncrement )++;
+ *
+ *     // If this callback has executed the required number of times, stop the
+ *     // timer.
+ *     if( *puxVariableToIncrement == 5 )
+ *     {
+ *         // This is called from a timer callback so must not block.
+ *         xTimerStop( xExpiredTimer, staticDONT_BLOCK );
+ *     }
+ * }
+ *
+ *
+ * void main( void )
+ * {
+ *     // Create the software time.  xTimerCreateStatic() has an extra parameter
+ *     // than the normal xTimerCreate() API function.  The parameter is a pointer
+ *     // to the StaticTimer_t structure that will hold the software timer
+ *     // structure.  If the parameter is passed as NULL then the structure will be
+ *     // allocated dynamically, just as if xTimerCreate() had been called.
+ *     xTimer = xTimerCreateStatic( "T1",             // Text name for the task.  Helps debugging only.  Not used by FreeRTOS.
+ *                                  xTimerPeriod,     // The period of the timer in ticks.
+ *                                  pdTRUE,           // This is an auto-reload timer.
+ *                                  ( void * ) &uxVariableToIncrement,    // A variable incremented by the software timer's callback function
+ *                                  prvTimerCallback, // The function to execute when the timer expires.
+ *                                  &xTimerBuffer );  // The buffer that will hold the software timer structure.
+ *
+ *     // The scheduler has not started yet so a block time is not used.
+ *     xReturned = xTimerStart( xTimer, 0 );
+ *
+ *     // ...
+ *     // Create tasks here.
+ *     // ...
+ *
+ *     // Starting the scheduler will start the timers running as they have already
+ *     // been set into the active state.
+ *     vTaskStartScheduler();
+ *
+ *     // Should not reach here.
+ *     for( ;; );
+ * }
+ * @endverbatim
+ */
+#if ( configSUPPORT_STATIC_ALLOCATION == 1 )
+    TimerHandle_t xTimerCreateStatic( const char * const pcTimerName, /*lint !e971 Unqualified char types are allowed for strings and single characters only. */
+                                      const TickType_t xTimerPeriodInTicks,
+                                      const UBaseType_t uxAutoReload,
+                                      void * const pvTimerID,
+                                      TimerCallbackFunction_t pxCallbackFunction,
+                                      StaticTimer_t * pxTimerBuffer );
+#endif /* configSUPPORT_STATIC_ALLOCATION */
+
+/**
+ * void *pvTimerGetTimerID( TimerHandle_t 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, and by calling the
+ * vTimerSetTimerID() API function.
+ *
+ * If the same callback function is assigned to multiple timers then the timer
+ * ID can be used as time specific (timer local) storage.
+ *
+ * @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( const TimerHandle_t xTimer );
+
+/**
+ * void vTimerSetTimerID( TimerHandle_t xTimer, void *pvNewID );
+ *
+ * Sets 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 as time specific (timer local) storage.
+ *
+ * @param xTimer The timer being updated.
+ *
+ * @param pvNewID The ID to assign to the timer.
+ *
+ * Example usage:
+ *
+ * See the xTimerCreate() API function example usage scenario.
+ */
+void vTimerSetTimerID( TimerHandle_t xTimer,
+                       void * pvNewID );
+
+/**
+ * BaseType_t xTimerIsTimerActive( TimerHandle_t 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 one-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:
+ * @verbatim
+ * // This function assumes xTimer has already been created.
+ * void vAFunction( TimerHandle_t 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.
+ *     }
+ * }
+ * @endverbatim
+ */
+BaseType_t xTimerIsTimerActive( TimerHandle_t xTimer );
+
+/**
+ * TaskHandle_t xTimerGetTimerDaemonTaskHandle( void );
+ *
+ * Simply returns the handle of the timer service/daemon task.  It it not valid
+ * to call xTimerGetTimerDaemonTaskHandle() before the scheduler has been started.
+ */
+TaskHandle_t xTimerGetTimerDaemonTaskHandle( void );
+
+/**
+ * BaseType_t xTimerStart( TimerHandle_t xTimer, TickType_t xTicksToWait );
+ *
+ * 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
+ * through 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 xTicksToWait 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.  xTicksToWait 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 xTicksToWait 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, xTicksToWait ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_START, ( xTaskGetTickCount() ), NULL, ( xTicksToWait ) )
+
+/**
+ * BaseType_t xTimerStop( TimerHandle_t xTimer, TickType_t xTicksToWait );
+ *
+ * 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
+ * through 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 xTicksToWait 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.  xTicksToWait 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 xTicksToWait 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, xTicksToWait ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_STOP, 0U, NULL, ( xTicksToWait ) )
+
+/**
+ * BaseType_t xTimerChangePeriod(   TimerHandle_t xTimer,
+ *                                  TickType_t xNewPeriod,
+ *                                  TickType_t xTicksToWait );
+ *
+ * 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
+ * through 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_PERIOD_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_PERIOD_MS ) provided configTICK_RATE_HZ is less than
+ * or equal to 1000.
+ *
+ * @param xTicksToWait 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.  xTicksToWait 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 xTicksToWait 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:
+ * @verbatim
+ * // 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( TimerHandle_t 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_PERIOD_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.
+ *         }
+ *     }
+ * }
+ * @endverbatim
+ */
+#define xTimerChangePeriod( xTimer, xNewPeriod, xTicksToWait ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_CHANGE_PERIOD, ( xNewPeriod ), NULL, ( xTicksToWait ) )
+
+/**
+ * BaseType_t xTimerDelete( TimerHandle_t xTimer, TickType_t xTicksToWait );
+ *
+ * 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
+ * through 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 xTicksToWait 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.  xTicksToWait 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 xTicksToWait 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, xTicksToWait ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_DELETE, 0U, NULL, ( xTicksToWait ) )
+
+/**
+ * BaseType_t xTimerReset( TimerHandle_t xTimer, TickType_t xTicksToWait );
+ *
+ * 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
+ * through 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 xTicksToWait 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.  xTicksToWait 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 xTicksToWait 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:
+ * @verbatim
+ * // 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.
+ *
+ * TimerHandle_t xBacklightTimer = NULL;
+ *
+ * // The callback function assigned to the one-shot timer.  In this case the
+ * // parameter is not used.
+ * void vBacklightTimerCallback( TimerHandle_t 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 )
+ * {
+ * int32_t 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_PERIOD_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.
+ *     vTaskStartScheduler();
+ *
+ *     // Should not reach here.
+ *     for( ;; );
+ * }
+ * @endverbatim
+ */
+#define xTimerReset( xTimer, xTicksToWait ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_RESET, ( xTaskGetTickCount() ), NULL, ( xTicksToWait ) )
+
+/**
+ * BaseType_t xTimerStartFromISR(   TimerHandle_t xTimer,
+ *                                  BaseType_t *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:
+ * @verbatim
+ * // 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( TimerHandle_t 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 )
+ * {
+ * BaseType_t 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).
+ *     }
+ * }
+ * @endverbatim
+ */
+#define xTimerStartFromISR( xTimer, pxHigherPriorityTaskWoken ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_START_FROM_ISR, ( xTaskGetTickCountFromISR() ), ( pxHigherPriorityTaskWoken ), 0U )
+
+/**
+ * BaseType_t xTimerStopFromISR(    TimerHandle_t xTimer,
+ *                                  BaseType_t *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:
+ * @verbatim
+ * // 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).
+ *     }
+ * }
+ * @endverbatim
+ */
+#define xTimerStopFromISR( xTimer, pxHigherPriorityTaskWoken ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_STOP_FROM_ISR, 0, ( pxHigherPriorityTaskWoken ), 0U )
+
+/**
+ * BaseType_t xTimerChangePeriodFromISR( TimerHandle_t xTimer,
+ *                                       TickType_t xNewPeriod,
+ *                                       BaseType_t *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_PERIOD_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_PERIOD_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:
+ * @verbatim
+ * // 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 )
+ * {
+ * BaseType_t 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).
+ *     }
+ * }
+ * @endverbatim
+ */
+#define xTimerChangePeriodFromISR( xTimer, xNewPeriod, pxHigherPriorityTaskWoken ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_CHANGE_PERIOD_FROM_ISR, ( xNewPeriod ), ( pxHigherPriorityTaskWoken ), 0U )
+
+/**
+ * BaseType_t xTimerResetFromISR(   TimerHandle_t xTimer,
+ *                                  BaseType_t *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:
+ * @verbatim
+ * // 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( TimerHandle_t 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 )
+ * {
+ * BaseType_t 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).
+ *     }
+ * }
+ * @endverbatim
+ */
+#define xTimerResetFromISR( xTimer, pxHigherPriorityTaskWoken ) \
+    xTimerGenericCommand( ( xTimer ), tmrCOMMAND_RESET_FROM_ISR, ( xTaskGetTickCountFromISR() ), ( pxHigherPriorityTaskWoken ), 0U )
+
+/**
+ * const char * const pcTimerGetName( TimerHandle_t xTimer );
+ *
+ * Returns the name that was assigned to a timer when the timer was created.
+ *
+ * @param xTimer The handle of the timer being queried.
+ *
+ * @return The name assigned to the timer specified by the xTimer parameter.
+ */
+const char * pcTimerGetName( TimerHandle_t xTimer );
+
+/**
+ * void vTimerSetReloadMode( TimerHandle_t xTimer, const UBaseType_t uxAutoReload );
+ *
+ * Updates a timer to be either an auto-reload timer, in which case the timer
+ * automatically resets itself each time it expires, or a one-shot timer, in
+ * which case the timer will only expire once unless it is manually restarted.
+ *
+ * @param xTimer The handle of the timer being updated.
+ *
+ * @param uxAutoReload If uxAutoReload is set to pdTRUE then the timer will
+ * expire repeatedly with a frequency set by the timer's period (see the
+ * xTimerPeriodInTicks parameter of the xTimerCreate() API function).  If
+ * uxAutoReload is set to pdFALSE then the timer will be a one-shot timer and
+ * enter the dormant state after it expires.
+ */
+void vTimerSetReloadMode( TimerHandle_t xTimer,
+                          const UBaseType_t uxAutoReload );
+
+/**
+ * UBaseType_t uxTimerGetReloadMode( TimerHandle_t xTimer );
+ *
+ * Queries a timer to determine if it is an auto-reload timer, in which case the timer
+ * automatically resets itself each time it expires, or a one-shot timer, in
+ * which case the timer will only expire once unless it is manually restarted.
+ *
+ * @param xTimer The handle of the timer being queried.
+ *
+ * @return If the timer is an auto-reload timer then pdTRUE is returned, otherwise
+ * pdFALSE is returned.
+ */
+UBaseType_t uxTimerGetReloadMode( TimerHandle_t xTimer );
+
+/**
+ * TickType_t xTimerGetPeriod( TimerHandle_t xTimer );
+ *
+ * Returns the period of a timer.
+ *
+ * @param xTimer The handle of the timer being queried.
+ *
+ * @return The period of the timer in ticks.
+ */
+TickType_t xTimerGetPeriod( TimerHandle_t xTimer );
+
+/**
+ * TickType_t xTimerGetExpiryTime( TimerHandle_t xTimer );
+ *
+ * Returns the time in ticks at which the timer will expire.  If this is less
+ * than the current tick count then the expiry time has overflowed from the
+ * current time.
+ *
+ * @param xTimer The handle of the timer being queried.
+ *
+ * @return If the timer is running then the time in ticks at which the timer
+ * will next expire is returned.  If the timer is not running then the return
+ * value is undefined.
+ */
+TickType_t xTimerGetExpiryTime( TimerHandle_t xTimer );
+
+/*
+ * Functions beyond this part are not part of the public API and are intended
+ * for use by the kernel only.
+ */
+BaseType_t xTimerGenericCommand( TimerHandle_t xTimer,
+                                 const BaseType_t xCommandID,
+                                 const TickType_t xOptionalValue,
+                                 BaseType_t * const pxHigherPriorityTaskWoken,
+                                 const TickType_t xTicksToWait );
+
+/* *INDENT-OFF* */
+#ifdef __cplusplus
+    }
+#endif
+/* *INDENT-ON* */
+#endif /* TIMERS_H */

FreeRTOS/timers.c

@@ -0,0 +1,328 @@
+/*
+ * FreeRTOS Kernel V10.4.6
+ * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
+ */
+
+/* Standard includes. */
+#include <stdlib.h>
+
+#include "FreeRTOS.h"
+#include "task.h"
+#include "queue.h"
+#include "timers.h"
+
+/* This entire source file will be skipped if the application is not configured
+ * to include software timer functionality.  This #if is closed at the very bottom
+ * of this file.  If you want to include software timer functionality then ensure
+ * configUSE_TIMERS is set to 1 in FreeRTOSConfig.h. */
+#if ( configUSE_TIMERS == 1 )
+
+    typedef void (* rt_timer_callback_t)(void *);
+
+/* The definition of the timers themselves. */
+    typedef struct tmrTimerControl
+    {
+        struct rt_timer timer;
+        void * pvTimerID;                           /*<< An ID to identify the timer.  This allows the timer to be identified when the same callback is used for multiple timers. */
+    } xTIMER;
+
+    typedef xTIMER Timer_t;
+
+/*-----------------------------------------------------------*/
+
+    #if ( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
+
+        TimerHandle_t xTimerCreate( const char * const pcTimerName,
+                                    const TickType_t xTimerPeriodInTicks,
+                                    const UBaseType_t uxAutoReload,
+                                    void * const pvTimerID,
+                                    TimerCallbackFunction_t pxCallbackFunction )
+        {
+            Timer_t * pxNewTimer;
+            rt_uint8_t flag = RT_TIMER_FLAG_SOFT_TIMER;
+
+            pxNewTimer = ( Timer_t * ) RT_KERNEL_MALLOC( sizeof( Timer_t ) );
+
+            if( pxNewTimer != RT_NULL )
+            {
+                if ( uxAutoReload != pdFALSE )
+                {
+                    flag |= RT_TIMER_FLAG_PERIODIC;
+                }
+                else
+                {
+                    flag |= RT_TIMER_FLAG_ONE_SHOT;
+                }
+                rt_timer_init( ( rt_timer_t ) pxNewTimer, pcTimerName, ( rt_timer_callback_t ) pxCallbackFunction, pxNewTimer, xTimerPeriodInTicks, flag );
+                pxNewTimer->pvTimerID = pvTimerID;
+                /* Mark as dynamic so we can distinguish when deleting */
+                ( ( rt_timer_t ) pxNewTimer )->parent.type &= ~RT_Object_Class_Static;
+            }
+
+            return pxNewTimer;
+        }
+
+    #endif /* configSUPPORT_DYNAMIC_ALLOCATION */
+/*-----------------------------------------------------------*/
+
+    #if ( configSUPPORT_STATIC_ALLOCATION == 1 )
+
+        TimerHandle_t xTimerCreateStatic( const char * const pcTimerName,
+                                          const TickType_t xTimerPeriodInTicks,
+                                          const UBaseType_t uxAutoReload,
+                                          void * const pvTimerID,
+                                          TimerCallbackFunction_t pxCallbackFunction,
+                                          StaticTimer_t * pxTimerBuffer )
+        {
+            Timer_t * pxNewTimer;
+            rt_uint8_t flag = RT_TIMER_FLAG_SOFT_TIMER;
+
+            #if ( configASSERT_DEFINED == 1 )
+                {
+                    /* Sanity check that the size of the structure used to declare a
+                     * variable of type StaticTimer_t equals the size of the real timer
+                     * structure. */
+                    volatile size_t xSize = sizeof( StaticTimer_t );
+                    configASSERT( xSize == sizeof( Timer_t ) );
+                    ( void ) xSize; /* Keeps lint quiet when configASSERT() is not defined. */
+                }
+            #endif /* configASSERT_DEFINED */
+
+            /* A pointer to a StaticTimer_t structure MUST be provided, use it. */
+            configASSERT( pxTimerBuffer );
+            pxNewTimer = ( Timer_t * ) pxTimerBuffer;
+
+            if( pxNewTimer != NULL )
+            {
+                if ( uxAutoReload != pdFALSE )
+                {
+                    flag |= RT_TIMER_FLAG_PERIODIC;
+                }
+                else
+                {
+                    flag |= RT_TIMER_FLAG_ONE_SHOT;
+                }
+                rt_timer_init( ( rt_timer_t ) pxNewTimer, pcTimerName, ( rt_timer_callback_t ) pxCallbackFunction, pxNewTimer, xTimerPeriodInTicks, flag );
+                pxNewTimer->pvTimerID = pvTimerID;
+            }
+
+            return pxNewTimer;
+        }
+
+    #endif /* configSUPPORT_STATIC_ALLOCATION */
+/*-----------------------------------------------------------*/
+
+    BaseType_t xTimerGenericCommand( TimerHandle_t xTimer,
+                                     const BaseType_t xCommandID,
+                                     const TickType_t xOptionalValue,
+                                     BaseType_t * const pxHigherPriorityTaskWoken,
+                                     const TickType_t xTicksToWait )
+    {
+        rt_err_t err = -RT_ERROR;
+
+        configASSERT( xTimer );
+
+        if ( ( xCommandID == tmrCOMMAND_START ) || ( xCommandID == tmrCOMMAND_START_FROM_ISR )
+             || ( xCommandID == tmrCOMMAND_RESET ) || ( xCommandID == tmrCOMMAND_RESET_FROM_ISR ) )
+        {
+            err = rt_timer_start( ( rt_timer_t ) xTimer );
+        }
+        else if ( ( xCommandID == tmrCOMMAND_STOP ) || ( xCommandID == tmrCOMMAND_STOP_FROM_ISR ) )
+        {
+            err = rt_timer_stop( ( rt_timer_t ) xTimer );
+        }
+        else if ( ( xCommandID == tmrCOMMAND_CHANGE_PERIOD ) || ( xCommandID == tmrCOMMAND_CHANGE_PERIOD_FROM_ISR ) )
+        {
+            if ( rt_timer_stop( ( rt_timer_t ) xTimer ) == RT_EOK )
+            {
+                if ( rt_timer_control( ( rt_timer_t ) xTimer, RT_TIMER_CTRL_SET_TIME, ( void * ) &xOptionalValue ) == RT_EOK )
+                {
+                    err = rt_timer_start( ( rt_timer_t ) xTimer );
+                }
+            }
+        }
+        else if ( xCommandID == tmrCOMMAND_DELETE )
+        {
+        #if ( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configSUPPORT_STATIC_ALLOCATION == 1 ) )
+            if ( rt_object_is_systemobject( ( rt_object_t ) xTimer ) )
+        #endif
+            {
+            #if ( configSUPPORT_STATIC_ALLOCATION == 1 )
+                err = rt_timer_detach( ( rt_timer_t ) xTimer );
+            #endif
+        #if ( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configSUPPORT_STATIC_ALLOCATION == 1 ) )
+            }
+            else
+            {
+        #endif
+            #if ( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
+                ( ( rt_timer_t ) xTimer )->parent.type |= RT_Object_Class_Static;
+                err = rt_timer_detach( ( rt_timer_t ) xTimer );
+                RT_KERNEL_FREE( xTimer );
+            #endif
+            }
+        }
+
+        if ( ( xCommandID >= tmrFIRST_FROM_ISR_COMMAND ) && ( xCommandID <= tmrCOMMAND_CHANGE_PERIOD_FROM_ISR ) && ( pxHigherPriorityTaskWoken != NULL ) )
+        {
+            *pxHigherPriorityTaskWoken = pdFALSE;
+        }
+
+        return rt_err_to_freertos( err );
+    }
+/*-----------------------------------------------------------*/
+
+    TaskHandle_t xTimerGetTimerDaemonTaskHandle( void )
+    {
+        return ( TaskHandle_t ) rt_thread_find( "timer" );
+    }
+/*-----------------------------------------------------------*/
+
+    TickType_t xTimerGetPeriod( TimerHandle_t xTimer )
+    {
+        Timer_t * pxTimer = xTimer;
+        rt_tick_t arg;
+
+        configASSERT( xTimer );
+        rt_timer_control( ( rt_timer_t ) pxTimer, RT_TIMER_CTRL_GET_TIME, &arg );
+
+        return ( TickType_t ) arg;
+    }
+/*-----------------------------------------------------------*/
+
+    void vTimerSetReloadMode( TimerHandle_t xTimer,
+                              const UBaseType_t uxAutoReload )
+    {
+        Timer_t * pxTimer = xTimer;
+
+        configASSERT( xTimer );
+        if ( uxAutoReload != pdFALSE )
+        {
+            rt_timer_control( ( rt_timer_t ) pxTimer, RT_TIMER_CTRL_SET_PERIODIC, RT_NULL );
+        }
+        else
+        {
+            rt_timer_control( ( rt_timer_t ) pxTimer, RT_TIMER_CTRL_SET_ONESHOT, RT_NULL );
+        }
+    }
+/*-----------------------------------------------------------*/
+
+    UBaseType_t uxTimerGetReloadMode( TimerHandle_t xTimer )
+    {
+        Timer_t * pxTimer = xTimer;
+        UBaseType_t uxReturn;
+        rt_base_t level;
+
+        configASSERT( xTimer );
+        level = rt_hw_interrupt_disable();
+        if ( ( ( rt_timer_t ) pxTimer )->parent.flag & RT_TIMER_FLAG_PERIODIC )
+        {
+            uxReturn = ( UBaseType_t ) pdTRUE;
+        }
+        else
+        {
+            uxReturn = ( UBaseType_t ) pdFALSE;
+        }
+        rt_hw_interrupt_enable( level );
+
+        return uxReturn;
+    }
+/*-----------------------------------------------------------*/
+
+    TickType_t xTimerGetExpiryTime( TimerHandle_t xTimer )
+    {
+        Timer_t * pxTimer = xTimer;
+        TickType_t xReturn;
+
+        configASSERT( xTimer );
+        rt_timer_control( ( rt_timer_t ) pxTimer, RT_TIMER_CTRL_GET_REMAIN_TIME, &xReturn );
+
+        return xReturn;
+    }
+/*-----------------------------------------------------------*/
+
+    const char * pcTimerGetName( TimerHandle_t xTimer )
+    {
+        Timer_t * pxTimer = xTimer;
+
+        configASSERT( xTimer );
+        return ( ( rt_timer_t ) pxTimer )->parent.name;
+    }
+/*-----------------------------------------------------------*/
+
+    BaseType_t xTimerIsTimerActive( TimerHandle_t xTimer )
+    {
+        BaseType_t xReturn;
+        Timer_t * pxTimer = xTimer;
+        rt_uint32_t arg;
+
+        configASSERT( xTimer );
+
+        rt_timer_control( ( rt_timer_t ) pxTimer, RT_TIMER_CTRL_GET_STATE, &arg );
+        if ( arg == RT_TIMER_FLAG_ACTIVATED )
+        {
+            xReturn = pdTRUE;
+        }
+        else
+        {
+            xReturn = pdFALSE;
+        }
+
+        return xReturn;
+    }
+/*-----------------------------------------------------------*/
+
+    void * pvTimerGetTimerID( const TimerHandle_t xTimer )
+    {
+        Timer_t * const pxTimer = xTimer;
+        void * pvReturn;
+        rt_base_t level;
+
+        configASSERT( xTimer );
+
+        level = rt_hw_interrupt_disable();
+        pvReturn = pxTimer->pvTimerID;
+        rt_hw_interrupt_enable( level );
+
+        return pvReturn;
+    }
+/*-----------------------------------------------------------*/
+
+    void vTimerSetTimerID( TimerHandle_t xTimer,
+                           void * pvNewID )
+    {
+        Timer_t * const pxTimer = xTimer;
+        rt_base_t level;
+
+        configASSERT( xTimer );
+
+        level = rt_hw_interrupt_disable();
+        pxTimer->pvTimerID = pvNewID;
+        rt_hw_interrupt_enable( level );
+    }
+/*-----------------------------------------------------------*/
+
+#endif /* configUSE_TIMERS == 1 */

test/test_timer.c

@@ -0,0 +1,56 @@
+/*
+ * Demo: timer
+ *
+ * This demo demonstrates using timers
+ *
+ */
+
+#include <FreeRTOS.h>
+#include <timers.h>
+
+static TimerHandle_t xTimer1 = NULL;
+static TimerHandle_t xTimer2 = NULL;
+static volatile UBaseType_t uxVariableToIncrement = 0;
+static StaticTimer_t xTimerBuffer;
+
+void prvTimerCallback(TimerHandle_t xTimer)
+{
+    UBaseType_t *puxVariableToIncrement;
+    rt_kprintf("%s time out, period: %d\n", pcTimerGetName(xTimer), xTimerGetPeriod(xTimer));
+    puxVariableToIncrement = (UBaseType_t *)pvTimerGetTimerID(xTimer);
+    if (puxVariableToIncrement != NULL)
+    {
+        (*puxVariableToIncrement)++;
+        rt_kprintf("Value: %d\n", *puxVariableToIncrement);
+        if (*puxVariableToIncrement == 5)
+        {
+            xTimerChangePeriod(xTimer, pdMS_TO_TICKS(1000), 0);
+        }
+        else if (*puxVariableToIncrement == 10)
+        {
+            xTimerStop(xTimer, 0);
+        }
+    }
+}
+
+int timer_sample(void)
+{
+    xTimer1 = xTimerCreate("Timer 1", pdMS_TO_TICKS(1000), pdFALSE, NULL, prvTimerCallback);
+    if (xTimer1 == NULL)
+    {
+        rt_kprintf("Create timer 1 failed");
+        return -1;
+    }
+    xTimer2 = xTimerCreateStatic("Timer 2", pdMS_TO_TICKS(500), pdTRUE, (void *)&uxVariableToIncrement, prvTimerCallback, &xTimerBuffer);
+    if (xTimer2 == NULL)
+    {
+        rt_kprintf("Create timer 2 failed");
+        return -1;
+    }
+    xTimerStart(xTimer1, 0);
+    xTimerStart(xTimer2, 0);
+
+    return 0;
+}
+
+MSH_CMD_EXPORT(timer_sample, timer sample);