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/*
* FreeRTOS Kernel V10.3.0
* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* http://www.FreeRTOS.org
* http://aws.amazon.com/freertos
*
* 1 tab == 4 spaces!
*/
/*
* High frequency timer test as described in main.c.
*/
/* Scheduler includes. */
#include "FreeRTOS.h"
/* Hardware specifics. */
#include "iodefine.h"
/* The set frequency of the interrupt. Deviations from this are measured as
the jitter. */
#define timerINTERRUPT_FREQUENCY ( 20000UL )
/* The expected time between each of the timer interrupts - if the jitter was
zero. */
#define timerEXPECTED_DIFFERENCE_VALUE ( ( unsigned short ) ( ( configPERIPHERAL_CLOCK_HZ / 8UL ) / timerINTERRUPT_FREQUENCY ) )
/* The highest available interrupt priority. */
#define timerHIGHEST_PRIORITY ( 15 )
/* Misc defines. */
#define timerTIMER_3_COUNT_VALUE ( *( ( unsigned short * ) 0x8801a ) ) /*( CMT3.CMCNT )*/
/*-----------------------------------------------------------*/
/* Interrupt handler in which the jitter is measured. */
static void prvTimer2IntHandler( void );
/* Stores the value of the maximum recorded jitter between interrupts. This is
displayed on one of the served web pages. */
volatile unsigned short usMaxJitter = 0;
/* Counts the number of high frequency interrupts - used to generate the run
time stats. */
volatile unsigned long ulHighFrequencyTickCount = 0UL;
/*-----------------------------------------------------------*/
void vSetupHighFrequencyTimer( void )
{
/* Timer CMT2 is used to generate the interrupts, and CMT3 is used
to measure the jitter. */
/* Enable compare match timer 2 and 3. */
MSTP( CMT2 ) = 0;
MSTP( CMT3 ) = 0;
/* Interrupt on compare match. */
CMT2.CMCR.BIT.CMIE = 1;
/* Set the compare match value. */
CMT2.CMCOR = ( unsigned short ) ( ( ( configPERIPHERAL_CLOCK_HZ / timerINTERRUPT_FREQUENCY ) -1 ) / 8 );
/* Divide the PCLK by 8. */
CMT2.CMCR.BIT.CKS = 0;
CMT3.CMCR.BIT.CKS = 0;
/* Enable the interrupt... */
_IEN( _CMT2_CMI2 ) = 1;
/* ...and set its priority to the maximum possible, this is above the priority
set by configMAX_SYSCALL_INTERRUPT_PRIORITY so will nest. */
_IPR( _CMT2_CMI2 ) = timerHIGHEST_PRIORITY;
/* Start the timers. */
CMT.CMSTR1.BIT.STR2 = 1;
CMT.CMSTR1.BIT.STR3 = 1;
}
/*-----------------------------------------------------------*/
#pragma interrupt ( prvTimer2IntHandler( vect = _VECT( _CMT2_CMI2 ), enable ) )
static void prvTimer2IntHandler( void )
{
volatile unsigned short usCurrentCount;
static unsigned short usMaxCount = 0;
static unsigned long ulErrorCount = 0UL;
/* We use the timer 1 counter value to measure the clock cycles between
the timer 0 interrupts. First stop the clock. */
CMT.CMSTR1.BIT.STR3 = 0;
nop();
nop();
usCurrentCount = timerTIMER_3_COUNT_VALUE;
/* Is this the largest count we have measured yet? */
if( usCurrentCount > usMaxCount )
{
if( usCurrentCount > timerEXPECTED_DIFFERENCE_VALUE )
{
usMaxJitter = usCurrentCount - timerEXPECTED_DIFFERENCE_VALUE;
}
else
{
/* This should not happen! */
ulErrorCount++;
}
usMaxCount = usCurrentCount;
}
/* Used to generate the run time stats. */
ulHighFrequencyTickCount++;
/* Clear the timer. */
timerTIMER_3_COUNT_VALUE = 0;
/* Then start the clock again. */
CMT.CMSTR1.BIT.STR3 = 1;
}
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