/* | |
FreeRTOS V7.4.1 - Copyright (C) 2013 Real Time Engineers Ltd. | |
FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME. PLEASE VISIT | |
http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION. | |
*************************************************************************** | |
* * | |
* 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 Real Time Engineers Ltd., 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, books, training, latest versions, | |
license and Real Time Engineers Ltd. contact details. | |
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products, | |
including FreeRTOS+Trace - an indispensable productivity tool, and our new | |
fully thread aware and reentrant UDP/IP stack. | |
http://www.OpenRTOS.com - 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.SafeRTOS.com - High Integrity Systems also provide a safety | |
engineered and independently SIL3 certified version for use in safety and | |
mission critical applications that require provable dependability. | |
*/ | |
/* 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; | |
} | |