2 FreeRTOS V7.1.1 - Copyright (C) 2012 Real Time Engineers Ltd.
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5 ***************************************************************************
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7 * FreeRTOS tutorial books are available in pdf and paperback. *
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8 * Complete, revised, and edited pdf reference manuals are also *
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11 * Purchasing FreeRTOS documentation will not only help you, by *
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12 * ensuring you get running as quickly as possible and with an *
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13 * in-depth knowledge of how to use FreeRTOS, it will also help *
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14 * the FreeRTOS project to continue with its mission of providing *
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15 * professional grade, cross platform, de facto standard solutions *
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16 * for microcontrollers - completely free of charge! *
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18 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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20 * Thank you for using FreeRTOS, and thank you for your support! *
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22 ***************************************************************************
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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 modification to the GPL is included to allow you to
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31 distribute a combined work that includes FreeRTOS without being obliged to
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32 provide the source code for proprietary components outside of the FreeRTOS
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33 kernel. FreeRTOS is distributed in the hope that it will be useful, but
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34 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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35 or 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 ***************************************************************************
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46 * Having a problem? Start by reading the FAQ "My application does *
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47 * not run, what could be wrong? *
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49 * http://www.FreeRTOS.org/FAQHelp.html *
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51 ***************************************************************************
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54 http://www.FreeRTOS.org - Documentation, training, latest information,
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55 license and contact details.
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57 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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58 including FreeRTOS+Trace - an indispensable productivity tool.
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60 Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
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61 the code with commercial support, indemnification, and middleware, under
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62 the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
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63 provide a safety engineered and independently SIL3 certified version under
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64 the SafeRTOS brand: http://www.SafeRTOS.com.
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67 /* High speed timer test as described in main.c. */
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70 /* Scheduler includes. */
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71 #include "FreeRTOS.h"
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73 /* Demo includes. */
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74 #include "partest.h"
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76 /* The number of interrupts to pass before we start looking at the jitter. */
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77 #define timerSETTLE_TIME 5
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79 /* The maximum value the 16bit timer can contain. */
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80 #define timerMAX_COUNT 0xffff
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82 /*-----------------------------------------------------------*/
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85 * Measure the time between this interrupt and the previous interrupt to
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86 * calculate the timing jitter. Remember the maximum value the jitter has
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87 * ever been calculated to be.
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89 static void prvCalculateAndStoreJitter( void );
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91 /*-----------------------------------------------------------*/
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93 /* The maximum time (in processor clocks) between two consecutive timer
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94 interrupts so far. */
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95 unsigned portSHORT usMaxJitter = 0;
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97 /*-----------------------------------------------------------*/
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99 void vSetupTimerTest( unsigned portSHORT usFrequencyHz )
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101 /* T2 is used to generate interrupts. T4 is used to provide an accurate
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102 time measurement. */
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108 /* Timer 2 is going to interrupt at usFrequencyHz Hz. */
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109 PR2 = ( unsigned portSHORT ) ( configCPU_CLOCK_HZ / ( unsigned portLONG ) usFrequencyHz );
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111 /* Timer 4 is going to free run from minimum to maximum value. */
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112 PR4 = ( unsigned portSHORT ) timerMAX_COUNT;
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114 /* Setup timer 2 interrupt priority to be above the kernel priority so
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115 the timer jitter is not effected by the kernel activity. */
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116 IPC1bits.T2IP = configKERNEL_INTERRUPT_PRIORITY + 1;
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118 /* Clear the interrupt as a starting condition. */
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121 /* Enable the interrupt. */
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124 /* Start both timers. */
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128 /*-----------------------------------------------------------*/
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130 static void prvCalculateAndStoreJitter( void )
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132 static unsigned portSHORT usLastCount = 0, usSettleCount = 0;
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133 unsigned portSHORT usThisCount, usDifference;
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135 /* Capture the timer value as we enter the interrupt. */
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136 usThisCount = TMR4;
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138 if( usSettleCount >= timerSETTLE_TIME )
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140 /* What is the difference between the timer value in this interrupt
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141 and the value from the last interrupt. */
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142 usDifference = usThisCount - usLastCount;
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144 /* Store the difference in the timer values if it is larger than the
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145 currently stored largest value. The difference over and above the
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146 expected difference will give the 'jitter' in the processing of these
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148 if( usDifference > usMaxJitter )
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150 usMaxJitter = usDifference;
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155 /* Don't bother storing any values for the first couple of
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160 /* Remember what the timer value was this time through, so we can calculate
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161 the difference the next time through. */
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162 usLastCount = usThisCount;
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164 /*-----------------------------------------------------------*/
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166 void __attribute__((__interrupt__, auto_psv)) _T2Interrupt( void )
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168 /* Work out the time between this and the previous interrupt. */
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169 prvCalculateAndStoreJitter();
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171 /* Clear the timer interrupt. */
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