2 FreeRTOS V7.4.2 - Copyright (C) 2013 Real Time Engineers Ltd.
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4 FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME. PLEASE VISIT
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5 http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 ***************************************************************************
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9 * FreeRTOS tutorial books are available in pdf and paperback. *
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10 * Complete, revised, and edited pdf reference manuals are also *
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13 * Purchasing FreeRTOS documentation will not only help you, by *
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14 * ensuring you get running as quickly as possible and with an *
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15 * in-depth knowledge of how to use FreeRTOS, it will also help *
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16 * the FreeRTOS project to continue with its mission of providing *
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17 * professional grade, cross platform, de facto standard solutions *
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18 * for microcontrollers - completely free of charge! *
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20 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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22 * Thank you for using FreeRTOS, and thank you for your support! *
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24 ***************************************************************************
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27 This file is part of the FreeRTOS distribution.
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29 FreeRTOS is free software; you can redistribute it and/or modify it under
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30 the terms of the GNU General Public License (version 2) as published by the
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31 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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33 >>>>>>NOTE<<<<<< The modification to the GPL is included to allow you to
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34 distribute a combined work that includes FreeRTOS without being obliged to
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35 provide the source code for proprietary components outside of the FreeRTOS
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38 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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39 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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40 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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41 details. You should have received a copy of the GNU General Public License
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42 and the FreeRTOS license exception along with FreeRTOS; if not it can be
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43 viewed here: http://www.freertos.org/a00114.html and also obtained by
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44 writing to Real Time Engineers Ltd., contact details for whom are available
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45 on the FreeRTOS WEB site.
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49 ***************************************************************************
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51 * Having a problem? Start by reading the FAQ "My application does *
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52 * not run, what could be wrong?" *
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54 * http://www.FreeRTOS.org/FAQHelp.html *
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56 ***************************************************************************
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59 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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60 license and Real Time Engineers Ltd. contact details.
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62 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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63 including FreeRTOS+Trace - an indispensable productivity tool, and our new
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64 fully thread aware and reentrant UDP/IP stack.
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66 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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67 Integrity Systems, who sell the code with commercial support,
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68 indemnification and middleware, under the OpenRTOS brand.
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70 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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71 engineered and independently SIL3 certified version for use in safety and
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72 mission critical applications that require provable dependability.
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75 /* High speed timer test as described in main.c. */
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78 /* Scheduler includes. */
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79 #include "FreeRTOS.h"
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81 /* Demo includes. */
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82 #include "partest.h"
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84 /* The number of interrupts to pass before we start looking at the jitter. */
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85 #define timerSETTLE_TIME 5
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87 /* The maximum value the 16bit timer can contain. */
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88 #define timerMAX_COUNT 0xffff
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90 /*-----------------------------------------------------------*/
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93 * Measure the time between this interrupt and the previous interrupt to
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94 * calculate the timing jitter. Remember the maximum value the jitter has
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95 * ever been calculated to be.
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97 static void prvCalculateAndStoreJitter( void );
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99 /*-----------------------------------------------------------*/
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101 /* The maximum time (in processor clocks) between two consecutive timer
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102 interrupts so far. */
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103 unsigned portSHORT usMaxJitter = 0;
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105 /*-----------------------------------------------------------*/
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107 void vSetupTimerTest( unsigned portSHORT usFrequencyHz )
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109 /* T2 is used to generate interrupts. T4 is used to provide an accurate
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110 time measurement. */
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116 /* Timer 2 is going to interrupt at usFrequencyHz Hz. */
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117 PR2 = ( unsigned portSHORT ) ( configCPU_CLOCK_HZ / ( unsigned portLONG ) usFrequencyHz );
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119 /* Timer 4 is going to free run from minimum to maximum value. */
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120 PR4 = ( unsigned portSHORT ) timerMAX_COUNT;
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122 /* Setup timer 2 interrupt priority to be above the kernel priority so
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123 the timer jitter is not effected by the kernel activity. */
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124 IPC1bits.T2IP = configKERNEL_INTERRUPT_PRIORITY + 1;
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126 /* Clear the interrupt as a starting condition. */
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129 /* Enable the interrupt. */
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132 /* Start both timers. */
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136 /*-----------------------------------------------------------*/
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138 static void prvCalculateAndStoreJitter( void )
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140 static unsigned portSHORT usLastCount = 0, usSettleCount = 0;
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141 unsigned portSHORT usThisCount, usDifference;
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143 /* Capture the timer value as we enter the interrupt. */
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144 usThisCount = TMR4;
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146 if( usSettleCount >= timerSETTLE_TIME )
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148 /* What is the difference between the timer value in this interrupt
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149 and the value from the last interrupt. */
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150 usDifference = usThisCount - usLastCount;
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152 /* Store the difference in the timer values if it is larger than the
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153 currently stored largest value. The difference over and above the
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154 expected difference will give the 'jitter' in the processing of these
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156 if( usDifference > usMaxJitter )
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158 usMaxJitter = usDifference;
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163 /* Don't bother storing any values for the first couple of
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168 /* Remember what the timer value was this time through, so we can calculate
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169 the difference the next time through. */
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170 usLastCount = usThisCount;
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172 /*-----------------------------------------------------------*/
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174 void __attribute__((__interrupt__, auto_psv)) _T2Interrupt( void )
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176 /* Work out the time between this and the previous interrupt. */
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177 prvCalculateAndStoreJitter();
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179 /* Clear the timer interrupt. */
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