2 FreeRTOS V7.6.0 - Copyright (C) 2013 Real Time Engineers Ltd.
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5 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 ***************************************************************************
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9 * FreeRTOS provides completely free yet professionally developed, *
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10 * robust, strictly quality controlled, supported, and cross *
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11 * platform software that has become a de facto standard. *
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13 * Help yourself get started quickly and support the FreeRTOS *
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14 * project by purchasing a FreeRTOS tutorial book, reference *
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15 * manual, or both from: http://www.FreeRTOS.org/Documentation *
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19 ***************************************************************************
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21 This file is part of the FreeRTOS distribution.
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23 FreeRTOS is free software; you can redistribute it and/or modify it under
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24 the terms of the GNU General Public License (version 2) as published by the
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25 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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27 >>! NOTE: The modification to the GPL is included to allow you to distribute
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28 >>! a combined work that includes FreeRTOS without being obliged to provide
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29 >>! the source code for proprietary components outside of the FreeRTOS
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32 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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33 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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34 FOR A PARTICULAR PURPOSE. Full license text is available from the following
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35 link: http://www.freertos.org/a00114.html
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39 ***************************************************************************
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41 * Having a problem? Start by reading the FAQ "My application does *
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42 * not run, what could be wrong?" *
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44 * http://www.FreeRTOS.org/FAQHelp.html *
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46 ***************************************************************************
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48 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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49 license and Real Time Engineers Ltd. contact details.
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51 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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52 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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53 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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55 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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56 Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
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57 licenses offer ticketed support, indemnification and middleware.
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59 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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60 engineered and independently SIL3 certified version for use in safety and
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61 mission critical applications that require provable dependability.
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66 /* High speed timer test as described in main.c. */
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69 /* Scheduler includes. */
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70 #include "FreeRTOS.h"
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72 /* Demo includes. */
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73 #include "partest.h"
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75 /* The number of interrupts to pass before we start looking at the jitter. */
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76 #define timerSETTLE_TIME 5
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78 /* The maximum value the 16bit timer can contain. */
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79 #define timerMAX_COUNT 0xffff
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81 /*-----------------------------------------------------------*/
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84 * Measure the time between this interrupt and the previous interrupt to
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85 * calculate the timing jitter. Remember the maximum value the jitter has
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86 * ever been calculated to be.
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88 static void prvCalculateAndStoreJitter( void );
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90 /*-----------------------------------------------------------*/
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92 /* The maximum time (in processor clocks) between two consecutive timer
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93 interrupts so far. */
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94 unsigned short usMaxJitter = 0;
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96 /*-----------------------------------------------------------*/
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98 void vSetupTimerTest( unsigned short usFrequencyHz )
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100 /* T2 is used to generate interrupts. T4 is used to provide an accurate
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101 time measurement. */
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107 /* Timer 2 is going to interrupt at usFrequencyHz Hz. */
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108 PR2 = ( unsigned short ) ( configCPU_CLOCK_HZ / ( unsigned long ) usFrequencyHz );
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110 /* Timer 4 is going to free run from minimum to maximum value. */
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111 PR4 = ( unsigned short ) timerMAX_COUNT;
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113 /* Setup timer 2 interrupt priority to be above the kernel priority so
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114 the timer jitter is not effected by the kernel activity. */
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115 IPC1bits.T2IP = configKERNEL_INTERRUPT_PRIORITY + 1;
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117 /* Clear the interrupt as a starting condition. */
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120 /* Enable the interrupt. */
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123 /* Start both timers. */
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127 /*-----------------------------------------------------------*/
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129 static void prvCalculateAndStoreJitter( void )
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131 static unsigned short usLastCount = 0, usSettleCount = 0;
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132 unsigned short usThisCount, usDifference;
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134 /* Capture the timer value as we enter the interrupt. */
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135 usThisCount = TMR4;
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137 if( usSettleCount >= timerSETTLE_TIME )
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139 /* What is the difference between the timer value in this interrupt
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140 and the value from the last interrupt. */
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141 usDifference = usThisCount - usLastCount;
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143 /* Store the difference in the timer values if it is larger than the
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144 currently stored largest value. The difference over and above the
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145 expected difference will give the 'jitter' in the processing of these
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147 if( usDifference > usMaxJitter )
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149 usMaxJitter = usDifference;
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154 /* Don't bother storing any values for the first couple of
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159 /* Remember what the timer value was this time through, so we can calculate
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160 the difference the next time through. */
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161 usLastCount = usThisCount;
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163 /*-----------------------------------------------------------*/
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165 void __attribute__((__interrupt__, auto_psv)) _T2Interrupt( void )
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167 /* Work out the time between this and the previous interrupt. */
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168 prvCalculateAndStoreJitter();
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170 /* Clear the timer interrupt. */
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