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/*
FreeRTOS V7.1.1 - Copyright (C) 2012 Real Time Engineers Ltd.
***************************************************************************
* *
* FreeRTOS tutorial books are available in pdf and paperback. *
* Complete, revised, and edited pdf reference manuals are also *
* available. *
* *
* Purchasing FreeRTOS documentation will not only help you, by *
* ensuring you get running as quickly as possible and with an *
* in-depth knowledge of how to use FreeRTOS, it will also help *
* the FreeRTOS project to continue with its mission of providing *
* professional grade, cross platform, de facto standard solutions *
* for microcontrollers - completely free of charge! *
* *
* >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
* *
* Thank you for using FreeRTOS, and thank you for your support! *
* *
***************************************************************************
This file is part of the FreeRTOS distribution.
FreeRTOS is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License (version 2) as published by the
Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
>>>NOTE<<< The modification to the GPL is included to allow you to
distribute a combined work that includes FreeRTOS without being obliged to
provide the source code for proprietary components outside of the FreeRTOS
kernel. FreeRTOS is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details. You should have received a copy of the GNU General Public
License and the FreeRTOS license exception along with FreeRTOS; if not it
can be viewed here: http://www.freertos.org/a00114.html and also obtained
by writing to Richard Barry, contact details for whom are available on the
FreeRTOS WEB site.
1 tab == 4 spaces!
***************************************************************************
* *
* Having a problem? Start by reading the FAQ "My application does *
* not run, what could be wrong? *
* *
* http://www.FreeRTOS.org/FAQHelp.html *
* *
***************************************************************************
http://www.FreeRTOS.org - Documentation, training, latest information,
license and contact details.
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
including FreeRTOS+Trace - an indispensable productivity tool.
Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
the code with commercial support, indemnification, and middleware, under
the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
provide a safety engineered and independently SIL3 certified version under
the SafeRTOS brand: http://www.SafeRTOS.com.
*/
/* High speed timer test as described in main.c. */
/* Scheduler includes. */
#include "FreeRTOS.h"
/* Demo includes. */
#include "partest.h"
/* The number of interrupts to pass before we start looking at the jitter. */
#define timerSETTLE_TIME 5
/* The maximum value the 16bit timer can contain. */
#define timerMAX_COUNT 0xffff
/*-----------------------------------------------------------*/
/*
* Measure the time between this interrupt and the previous interrupt to
* calculate the timing jitter. Remember the maximum value the jitter has
* ever been calculated to be.
*/
static void prvCalculateAndStoreJitter( void );
/*-----------------------------------------------------------*/
/* The maximum time (in processor clocks) between two consecutive timer
interrupts so far. */
unsigned portSHORT usMaxJitter = 0;
/*-----------------------------------------------------------*/
void vSetupTimerTest( unsigned portSHORT usFrequencyHz )
{
/* T2 is used to generate interrupts. T4 is used to provide an accurate
time measurement. */
T2CON = 0;
T4CON = 0;
TMR2 = 0;
TMR4 = 0;
/* Timer 2 is going to interrupt at usFrequencyHz Hz. */
PR2 = ( unsigned portSHORT ) ( configCPU_CLOCK_HZ / ( unsigned portLONG ) usFrequencyHz );
/* Timer 4 is going to free run from minimum to maximum value. */
PR4 = ( unsigned portSHORT ) timerMAX_COUNT;
/* Setup timer 2 interrupt priority to be above the kernel priority so
the timer jitter is not effected by the kernel activity. */
IPC1bits.T2IP = configKERNEL_INTERRUPT_PRIORITY + 1;
/* Clear the interrupt as a starting condition. */
IFS0bits.T2IF = 0;
/* Enable the interrupt. */
IEC0bits.T2IE = 1;
/* Start both timers. */
T2CONbits.TON = 1;
T4CONbits.TON = 1;
}
/*-----------------------------------------------------------*/
static void prvCalculateAndStoreJitter( void )
{
static unsigned portSHORT usLastCount = 0, usSettleCount = 0;
unsigned portSHORT usThisCount, usDifference;
/* Capture the timer value as we enter the interrupt. */
usThisCount = TMR4;
if( usSettleCount >= timerSETTLE_TIME )
{
/* What is the difference between the timer value in this interrupt
and the value from the last interrupt. */
usDifference = usThisCount - usLastCount;
/* Store the difference in the timer values if it is larger than the
currently stored largest value. The difference over and above the
expected difference will give the 'jitter' in the processing of these
interrupts. */
if( usDifference > usMaxJitter )
{
usMaxJitter = usDifference;
}
}
else
{
/* Don't bother storing any values for the first couple of
interrupts. */
usSettleCount++;
}
/* Remember what the timer value was this time through, so we can calculate
the difference the next time through. */
usLastCount = usThisCount;
}
/*-----------------------------------------------------------*/
void __attribute__((__interrupt__, auto_psv)) _T2Interrupt( void )
{
/* Work out the time between this and the previous interrupt. */
prvCalculateAndStoreJitter();
/* Clear the timer interrupt. */
IFS0bits.T2IF = 0;
}
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