2 FreeRTOS V6.0.5 - 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 eBook *
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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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55 * High frequency timer test as described in main.c.
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58 /* Scheduler includes. */
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59 #include "FreeRTOS.h"
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61 /* Hardware specifics. */
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62 #include "iodefine.h"
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64 /* The set frequency of the interrupt. Deviations from this are measured as
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66 #define timerINTERRUPT_FREQUENCY ( 20000UL )
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68 /* The expected time between each of the timer interrupts - if the jitter was
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70 #define timerEXPECTED_DIFFERENCE_VALUE ( ( unsigned short ) ( ( configPERIPHERAL_CLOCK_HZ / 8UL ) / timerINTERRUPT_FREQUENCY ) )
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72 /* The highest available interrupt priority. */
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73 #define timerHIGHEST_PRIORITY ( 15 )
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76 #define timerTIMER_3_COUNT_VALUE ( *( ( unsigned short * ) 0x8801a ) ) /*( CMT3.CMCNT )*/
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78 /*-----------------------------------------------------------*/
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80 /* Interrupt handler in which the jitter is measured. */
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81 static void prvTimer2IntHandler( void );
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83 /* Stores the value of the maximum recorded jitter between interrupts. */
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84 volatile unsigned short usMaxJitter = 0;
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86 /*-----------------------------------------------------------*/
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88 void vSetupHighFrequencyTimer( void )
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90 /* Timer CMT2 is used to generate the interrupts, and CMT3 is used
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91 to measure the jitter. */
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93 /* Enable compare match timer 2 and 3. */
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97 /* Interrupt on compare match. */
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98 CMT2.CMCR.BIT.CMIE = 1;
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100 /* Set the compare match value. */
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101 CMT2.CMCOR = ( unsigned short ) ( ( ( configPERIPHERAL_CLOCK_HZ / timerINTERRUPT_FREQUENCY ) -1 ) / 8 );
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103 /* Divide the PCLK by 8. */
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104 CMT2.CMCR.BIT.CKS = 0;
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105 CMT3.CMCR.BIT.CKS = 0;
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107 /* Enable the interrupt... */
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108 _IEN( _CMT2_CMI2 ) = 1;
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110 /* ...and set its priority to the maximum possible, this is above the priority
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111 set by configMAX_SYSCALL_INTERRUPT_PRIORITY so will nest. */
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112 _IPR( _CMT2_CMI2 ) = timerHIGHEST_PRIORITY;
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114 /* Start the timers. */
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115 CMT.CMSTR1.BIT.STR2 = 1;
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116 CMT.CMSTR1.BIT.STR3 = 1;
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118 /*-----------------------------------------------------------*/
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120 #pragma interrupt ( prvTimer2IntHandler( vect = _VECT( _CMT2_CMI2 ), enable ) )
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121 static void prvTimer2IntHandler( void )
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123 volatile unsigned short usCurrentCount;
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124 static unsigned short usMaxCount = 0;
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125 static unsigned long ulErrorCount = 0UL;
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127 /* We use the timer 1 counter value to measure the clock cycles between
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128 the timer 0 interrupts. First stop the clock. */
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129 CMT.CMSTR1.BIT.STR3 = 0;
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132 usCurrentCount = timerTIMER_3_COUNT_VALUE;
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134 /* Is this the largest count we have measured yet? */
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135 if( usCurrentCount > usMaxCount )
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137 if( usCurrentCount > timerEXPECTED_DIFFERENCE_VALUE )
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139 usMaxJitter = usCurrentCount - timerEXPECTED_DIFFERENCE_VALUE;
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143 /* This should not happen! */
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147 usMaxCount = usCurrentCount;
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150 /* Clear the timer. */
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151 timerTIMER_3_COUNT_VALUE = 0;
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153 /* Then start the clock again. */
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154 CMT.CMSTR1.BIT.STR3 = 1;
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