FreeRTOS/Common/Minimal/flash.c

   1 /*
   2     FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd.
   3
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  24
  25     This file is part of the FreeRTOS distribution.
  26
  27     FreeRTOS is free software; you can redistribute it and/or modify it under
  28     the terms of the GNU General Public License (version 2) as published by the
  29     Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
  30     ***NOTE*** The exception to the GPL is included to allow you to distribute
  31     a combined work that includes FreeRTOS without being obliged to provide the
  32     source code for proprietary components outside of the FreeRTOS kernel.
  33     FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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  35     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  36     more details. You should have received a copy of the GNU General Public
  37     License and the FreeRTOS license exception along with FreeRTOS; if not it
  38     can be viewed here: http://www.freertos.org/a00114.html and also obtained
  39     by writing to Richard Barry, contact details for whom are available on the
  40     FreeRTOS WEB site.
  41
  42     1 tab == 4 spaces!
  43
  44     http://www.FreeRTOS.org - Documentation, latest information, license and
  45     contact details.
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  52 */
  53
  54 /**
  55  * This version of flash .c is for use on systems that have limited stack space
  56  * and no display facilities.  The complete version can be found in the
  57  * Demo/Common/Full directory.
  58  *
  59  * Three tasks are created, each of which flash an LED at a different rate.  The first
  60  * LED flashes every 200ms, the second every 400ms, the third every 600ms.
  61  *
  62  * The LED flash tasks provide instant visual feedback.  They show that the scheduler
  63  * is still operational.
  64  *
  65  */
  66
  67
  68 #include <stdlib.h>
  69
  70 /* Scheduler include files. */
  71 #include "FreeRTOS.h"
  72 #include "task.h"
  73
  74 /* Demo program include files. */
  75 #include "partest.h"
  76 #include "flash.h"
  77
  78 #define ledSTACK_SIZE           configMINIMAL_STACK_SIZE
  79 #define ledNUMBER_OF_LEDS       ( 3 )
  80 #define ledFLASH_RATE_BASE      ( ( portTickType ) 333 )
  81
  82 /* Variable used by the created tasks to calculate the LED number to use, and
  83 the rate at which they should flash the LED. */
  84 static volatile unsigned portBASE_TYPE uxFlashTaskNumber = 0;
  85
  86 /* The task that is created three times. */
  87 static portTASK_FUNCTION_PROTO( vLEDFlashTask, pvParameters );
  88
  89 /*-----------------------------------------------------------*/
  90
  91 void vStartLEDFlashTasks( unsigned portBASE_TYPE uxPriority )
  92 {
  93 signed portBASE_TYPE xLEDTask;
  94
  95         /* Create the three tasks. */
  96         for( xLEDTask = 0; xLEDTask < ledNUMBER_OF_LEDS; ++xLEDTask )
  97         {
  98                 /* Spawn the task. */
  99                 xTaskCreate( vLEDFlashTask, ( signed char * ) "LEDx", ledSTACK_SIZE, NULL, uxPriority, ( xTaskHandle * ) NULL );
 100         }
 101 }
 102 /*-----------------------------------------------------------*/
 103
 104 static portTASK_FUNCTION( vLEDFlashTask, pvParameters )
 105 {
 106 portTickType xFlashRate, xLastFlashTime;
 107 unsigned portBASE_TYPE uxLED;
 108
 109         /* The parameters are not used. */
 110         ( void ) pvParameters;
 111
 112         /* Calculate the LED and flash rate. */
 113         portENTER_CRITICAL();
 114         {
 115                 /* See which of the eight LED's we should use. */
 116                 uxLED = uxFlashTaskNumber;
 117
 118                 /* Update so the next task uses the next LED. */
 119                 uxFlashTaskNumber++;
 120         }
 121         portEXIT_CRITICAL();
 122
 123         xFlashRate = ledFLASH_RATE_BASE + ( ledFLASH_RATE_BASE * ( portTickType ) uxLED );
 124         xFlashRate /= portTICK_RATE_MS;
 125
 126         /* We will turn the LED on and off again in the delay period, so each
 127         delay is only half the total period. */
 128         xFlashRate /= ( portTickType ) 2;
 129
 130         /* We need to initialise xLastFlashTime prior to the first call to
 131         vTaskDelayUntil(). */
 132         xLastFlashTime = xTaskGetTickCount();
 133
 134         for(;;)
 135         {
 136                 /* Delay for half the flash period then turn the LED on. */
 137                 vTaskDelayUntil( &xLastFlashTime, xFlashRate );
 138                 vParTestToggleLED( uxLED );
 139
 140                 /* Delay for half the flash period then turn the LED off. */
 141                 vTaskDelayUntil( &xLastFlashTime, xFlashRate );
 142                 vParTestToggleLED( uxLED );
 143         }
 144 } /*lint !e715 !e818 !e830 Function definition must be standard for task creation. */
 145