2 FreeRTOS V7.5.1 - Copyright (C) 2013 Real Time Engineers Ltd.
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4 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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6 ***************************************************************************
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8 * FreeRTOS provides completely free yet professionally developed, *
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9 * robust, strictly quality controlled, supported, and cross *
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10 * platform software that has become a de facto standard. *
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12 * Help yourself get started quickly and support the FreeRTOS *
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13 * project by purchasing a FreeRTOS tutorial book, reference *
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14 * manual, or both from: http://www.FreeRTOS.org/Documentation *
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18 ***************************************************************************
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20 This file is part of the FreeRTOS distribution.
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22 FreeRTOS is free software; you can redistribute it and/or modify it under
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23 the terms of the GNU General Public License (version 2) as published by the
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24 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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26 >>! NOTE: The modification to the GPL is included to allow you to distribute
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27 >>! a combined work that includes FreeRTOS without being obliged to provide
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28 >>! the source code for proprietary components outside of the FreeRTOS
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31 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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32 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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33 FOR A PARTICULAR PURPOSE. Full license text is available from the following
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34 link: http://www.freertos.org/a00114.html
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38 ***************************************************************************
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40 * Having a problem? Start by reading the FAQ "My application does *
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41 * not run, what could be wrong?" *
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43 * http://www.FreeRTOS.org/FAQHelp.html *
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45 ***************************************************************************
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47 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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48 license and Real Time Engineers Ltd. contact details.
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50 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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51 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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52 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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54 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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55 Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
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56 licenses offer ticketed support, indemnification and middleware.
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58 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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59 engineered and independently SIL3 certified version for use in safety and
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60 mission critical applications that require provable dependability.
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65 /* High speed timer test as described in main.c. */
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68 /* Scheduler includes. */
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69 #include "FreeRTOS.h"
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71 /* Demo includes. */
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72 #include "partest.h"
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74 /* The number of interrupts to pass before we start looking at the jitter. */
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75 #define timerSETTLE_TIME 5
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77 /* The maximum value the 16bit timer can contain. */
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78 #define timerMAX_COUNT 0xffff
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80 /*-----------------------------------------------------------*/
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83 * Measure the time between this interrupt and the previous interrupt to
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84 * calculate the timing jitter. Remember the maximum value the jitter has
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85 * ever been calculated to be.
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87 static void prvCalculateAndStoreJitter( void );
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89 /*-----------------------------------------------------------*/
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91 /* The maximum time (in processor clocks) between two consecutive timer
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92 interrupts so far. */
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93 unsigned portSHORT usMaxJitter = 0;
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95 /*-----------------------------------------------------------*/
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97 void vSetupTimerTest( unsigned portSHORT usFrequencyHz )
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99 /* T2 is used to generate interrupts. T4 is used to provide an accurate
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100 time measurement. */
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106 /* Timer 2 is going to interrupt at usFrequencyHz Hz. */
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107 PR2 = ( unsigned portSHORT ) ( configCPU_CLOCK_HZ / ( unsigned portLONG ) usFrequencyHz );
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109 /* Timer 4 is going to free run from minimum to maximum value. */
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110 PR4 = ( unsigned portSHORT ) timerMAX_COUNT;
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112 /* Setup timer 2 interrupt priority to be above the kernel priority so
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113 the timer jitter is not effected by the kernel activity. */
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114 IPC1bits.T2IP = configKERNEL_INTERRUPT_PRIORITY + 1;
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116 /* Clear the interrupt as a starting condition. */
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119 /* Enable the interrupt. */
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122 /* Start both timers. */
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126 /*-----------------------------------------------------------*/
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128 static void prvCalculateAndStoreJitter( void )
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130 static unsigned portSHORT usLastCount = 0, usSettleCount = 0;
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131 unsigned portSHORT usThisCount, usDifference;
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133 /* Capture the timer value as we enter the interrupt. */
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134 usThisCount = TMR4;
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136 if( usSettleCount >= timerSETTLE_TIME )
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138 /* What is the difference between the timer value in this interrupt
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139 and the value from the last interrupt. */
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140 usDifference = usThisCount - usLastCount;
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142 /* Store the difference in the timer values if it is larger than the
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143 currently stored largest value. The difference over and above the
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144 expected difference will give the 'jitter' in the processing of these
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146 if( usDifference > usMaxJitter )
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148 usMaxJitter = usDifference;
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153 /* Don't bother storing any values for the first couple of
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158 /* Remember what the timer value was this time through, so we can calculate
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159 the difference the next time through. */
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160 usLastCount = usThisCount;
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162 /*-----------------------------------------------------------*/
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164 void __attribute__((__interrupt__, auto_psv)) _T2Interrupt( void )
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166 /* Work out the time between this and the previous interrupt. */
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167 prvCalculateAndStoreJitter();
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169 /* Clear the timer interrupt. */
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