2 * FreeRTOS Kernel V10.3.0
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3 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software.
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 * http://www.FreeRTOS.org
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23 * http://aws.amazon.com/freertos
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25 * 1 tab == 4 spaces!
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29 * High frequency timer test as described in main.c.
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32 /* Scheduler includes. */
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33 #include "FreeRTOS.h"
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35 /* The set frequency of the interrupt. Deviations from this are measured as
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37 #define timerINTERRUPT_FREQUENCY ( 20000UL )
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39 /* The expected time between each of the timer interrupts - if the jitter was
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41 #define timerEXPECTED_DIFFERENCE_VALUE ( ( unsigned short ) ( ( configPERIPHERAL_CLOCK_HZ / 8UL ) / timerINTERRUPT_FREQUENCY ) )
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43 /* The highest available interrupt priority. */
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44 #define timerHIGHEST_PRIORITY ( 15 )
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47 #define timerTIMER_3_COUNT_VALUE ( *( ( unsigned short * ) 0x8801a ) ) /*( CMT3.CMCNT )*/
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49 /*-----------------------------------------------------------*/
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51 /* Interrupt handler in which the jitter is measured. */
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52 static void prvTimer2IntHandler( void );
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54 /* Stores the value of the maximum recorded jitter between interrupts. This is
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55 displayed on one of the served web pages. */
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56 volatile unsigned short usMaxJitter = 0;
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58 /* Counts the number of high frequency interrupts - used to generate the run
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60 volatile unsigned long ulHighFrequencyTickCount = 0UL;
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62 /*-----------------------------------------------------------*/
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64 void vSetupHighFrequencyTimer( void )
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66 /* Timer CMT2 is used to generate the interrupts, and CMT3 is used
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67 to measure the jitter. */
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69 /* Enable compare match timer 2 and 3. */
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73 /* Interrupt on compare match. */
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74 CMT2.CMCR.BIT.CMIE = 1;
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76 /* Set the compare match value. */
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77 CMT2.CMCOR = ( unsigned short ) ( ( ( configPERIPHERAL_CLOCK_HZ / timerINTERRUPT_FREQUENCY ) -1 ) / 8 );
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79 /* Divide the PCLK by 8. */
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80 CMT2.CMCR.BIT.CKS = 0;
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81 CMT3.CMCR.BIT.CKS = 0;
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83 /* Enable the interrupt... */
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84 _IEN( _CMT2_CMI2 ) = 1;
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86 /* ...and set its priority to the maximum possible, this is above the priority
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87 set by configMAX_SYSCALL_INTERRUPT_PRIORITY so will nest. */
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88 _IPR( _CMT2_CMI2 ) = timerHIGHEST_PRIORITY;
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90 /* Start the timers. */
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91 CMT.CMSTR1.BIT.STR2 = 1;
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92 CMT.CMSTR1.BIT.STR3 = 1;
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94 /*-----------------------------------------------------------*/
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96 #pragma interrupt ( prvTimer2IntHandler( vect = _VECT( _CMT2_CMI2 ), enable ) )
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97 static void prvTimer2IntHandler( void )
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99 volatile unsigned short usCurrentCount;
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100 static unsigned short usMaxCount = 0;
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101 static unsigned long ulErrorCount = 0UL;
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103 /* We use the timer 1 counter value to measure the clock cycles between
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104 the timer 0 interrupts. First stop the clock. */
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105 CMT.CMSTR1.BIT.STR3 = 0;
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108 usCurrentCount = timerTIMER_3_COUNT_VALUE;
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110 /* Is this the largest count we have measured yet? */
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111 if( usCurrentCount > usMaxCount )
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113 if( usCurrentCount > timerEXPECTED_DIFFERENCE_VALUE )
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115 usMaxJitter = usCurrentCount - timerEXPECTED_DIFFERENCE_VALUE;
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119 /* This should not happen! */
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123 usMaxCount = usCurrentCount;
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126 /* Used to generate the run time stats. */
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127 ulHighFrequencyTickCount++;
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129 /* Clear the timer. */
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130 timerTIMER_3_COUNT_VALUE = 0;
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132 /* Then start the clock again. */
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133 CMT.CMSTR1.BIT.STR3 = 1;
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