2 FreeRTOS V6.1.0 - Copyright (C) 2010 Real Time Engineers Ltd.
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4 ***************************************************************************
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8 * + New to FreeRTOS, *
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9 * + Wanting to learn FreeRTOS or multitasking in general quickly *
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10 * + Looking for basic training, *
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11 * + Wanting to improve your FreeRTOS skills and productivity *
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13 * then take a look at the FreeRTOS books - available as PDF or paperback *
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15 * "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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16 * http://www.FreeRTOS.org/Documentation *
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18 * A pdf reference manual is also available. Both are usually delivered *
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19 * to your inbox within 20 minutes to two hours when purchased between 8am *
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20 * and 8pm GMT (although please allow up to 24 hours in case of *
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21 * exceptional circumstances). Thank you for your support! *
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23 ***************************************************************************
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25 This file is part of the FreeRTOS distribution.
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27 FreeRTOS is free software; you can redistribute it and/or modify it under
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28 the terms of the GNU General Public License (version 2) as published by the
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29 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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30 ***NOTE*** The exception to the GPL is included to allow you to distribute
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31 a combined work that includes FreeRTOS without being obliged to provide the
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32 source code for proprietary components outside of the FreeRTOS kernel.
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33 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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34 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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35 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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36 more details. You should have received a copy of the GNU General Public
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37 License and the FreeRTOS license exception along with FreeRTOS; if not it
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38 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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39 by writing to Richard Barry, contact details for whom are available on the
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44 http://www.FreeRTOS.org - Documentation, latest information, license and
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47 http://www.SafeRTOS.com - A version that is certified for use in safety
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50 http://www.OpenRTOS.com - Commercial support, development, porting,
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51 licensing and training services.
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54 /* High speed timer test as described in main.c. */
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56 /* Scheduler includes. */
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57 #include "FreeRTOS.h"
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59 /* Library includes. */
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60 #include "hw_ints.h"
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61 #include "hw_memmap.h"
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62 #include "hw_types.h"
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63 #include "interrupt.h"
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65 #include "lmi_timer.h"
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66 #include "hw_timer.h"
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68 /* The set frequency of the interrupt. Deviations from this are measured as
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70 #define timerINTERRUPT_FREQUENCY ( 20000UL )
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72 /* The expected time between each of the timer interrupts - if the jitter was
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74 #define timerEXPECTED_DIFFERENCE_VALUE ( configCPU_CLOCK_HZ / timerINTERRUPT_FREQUENCY )
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76 /* The highest available interrupt priority. */
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77 #define timerHIGHEST_PRIORITY ( 0 )
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80 #define timerMAX_32BIT_VALUE ( 0xffffffffUL )
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81 #define timerTIMER_1_COUNT_VALUE ( * ( ( volatile unsigned long * ) ( ( unsigned portLONG ) TIMER1_BASE + 0x48UL ) ) )
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83 /*-----------------------------------------------------------*/
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85 /* Interrupt handler in which the jitter is measured. */
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86 void Timer0IntHandler( void );
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88 /* Stores the value of the maximum recorded jitter between interrupts. */
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89 volatile unsigned portLONG ulMaxJitter = 0;
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91 /*-----------------------------------------------------------*/
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93 void vSetupHighFrequencyTimer( void )
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95 unsigned long ulFrequency;
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97 /* Timer zero is used to generate the interrupts, and timer 1 is used
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98 to measure the jitter. */
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99 SysCtlPeripheralEnable( SYSCTL_PERIPH_TIMER0 );
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100 SysCtlPeripheralEnable( SYSCTL_PERIPH_TIMER1 );
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101 TimerConfigure( TIMER0_BASE, TIMER_CFG_32_BIT_PER );
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102 TimerConfigure( TIMER1_BASE, TIMER_CFG_32_BIT_PER );
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104 /* Set the timer interrupt to be above the kernel - highest. */
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105 IntPrioritySet( INT_TIMER0A, timerHIGHEST_PRIORITY );
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107 /* Just used to measure time. */
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108 TimerLoadSet(TIMER1_BASE, TIMER_A, timerMAX_32BIT_VALUE );
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110 /* Ensure interrupts do not start until the scheduler is running. */
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111 portDISABLE_INTERRUPTS();
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113 /* The rate at which the timer will interrupt. */
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114 ulFrequency = configCPU_CLOCK_HZ / timerINTERRUPT_FREQUENCY;
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115 TimerLoadSet( TIMER0_BASE, TIMER_A, ulFrequency );
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116 IntEnable( INT_TIMER0A );
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117 TimerIntEnable( TIMER0_BASE, TIMER_TIMA_TIMEOUT );
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119 /* Enable both timers. */
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120 TimerEnable( TIMER0_BASE, TIMER_A );
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121 TimerEnable( TIMER1_BASE, TIMER_A );
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123 /*-----------------------------------------------------------*/
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125 void Timer0IntHandler( void )
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127 unsigned portLONG ulDifference;
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128 volatile unsigned portLONG ulCurrentCount;
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129 static unsigned portLONG ulMaxDifference = 0, ulLastCount = 0;
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131 /* We use the timer 1 counter value to measure the clock cycles between
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132 the timer 0 interrupts. */
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133 ulCurrentCount = timerTIMER_1_COUNT_VALUE;
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135 TimerIntClear( TIMER0_BASE, TIMER_TIMA_TIMEOUT );
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137 if( ulCurrentCount < ulLastCount )
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139 /* How many times has timer 1 counted since the last interrupt? */
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140 ulDifference = ulLastCount - ulCurrentCount;
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142 /* Is this the largest difference we have measured yet? */
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143 if( ulDifference > ulMaxDifference )
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145 ulMaxDifference = ulDifference;
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146 ulMaxJitter = ulMaxDifference - timerEXPECTED_DIFFERENCE_VALUE;
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150 ulLastCount = ulCurrentCount;
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