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[/] [openrisc/] [trunk/] [rtos/] [freertos-6.1.1/] [Demo/] [PIC24_MPLAB/] [timertest.c] - Blame information for rev 589

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1 587 jeremybenn
/*
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    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
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    ***************************************************************************
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    *                                                                         *
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    * If you are:                                                             *
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    *                                                                         *
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    *    + New to FreeRTOS,                                                   *
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    *    + Wanting to learn FreeRTOS or multitasking in general quickly       *
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    *    + Looking for basic training,                                        *
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    *    + Wanting to improve your FreeRTOS skills and productivity           *
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    *                                                                         *
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    * then take a look at the FreeRTOS books - available as PDF or paperback  *
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    *                                                                         *
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    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *
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    *                  http://www.FreeRTOS.org/Documentation                  *
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    *                                                                         *
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    * A pdf reference manual is also available.  Both are usually delivered   *
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    * to your inbox within 20 minutes to two hours when purchased between 8am *
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    * and 8pm GMT (although please allow up to 24 hours in case of            *
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    * exceptional circumstances).  Thank you for your support!                *
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    *                                                                         *
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    ***************************************************************************
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    This file is part of the FreeRTOS distribution.
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    FreeRTOS is free software; you can redistribute it and/or modify it under
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    the terms of the GNU General Public License (version 2) as published by the
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    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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    ***NOTE*** The exception to the GPL is included to allow you to distribute
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    a combined work that includes FreeRTOS without being obliged to provide the
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    source code for proprietary components outside of the FreeRTOS kernel.
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    FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
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    more details. You should have received a copy of the GNU General Public
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    License and the FreeRTOS license exception along with FreeRTOS; if not it
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    can be viewed here: http://www.freertos.org/a00114.html and also obtained
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    by writing to Richard Barry, contact details for whom are available on the
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    FreeRTOS WEB site.
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    1 tab == 4 spaces!
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    http://www.FreeRTOS.org - Documentation, latest information, license and
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    contact details.
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    http://www.SafeRTOS.com - A version that is certified for use in safety
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    critical systems.
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    http://www.OpenRTOS.com - Commercial support, development, porting,
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    licensing and training services.
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*/
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/* High speed timer test as described in main.c. */
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/* Scheduler includes. */
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#include "FreeRTOS.h"
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/* Demo includes. */
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#include "partest.h"
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/* The number of interrupts to pass before we start looking at the jitter. */
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#define timerSETTLE_TIME                        5
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/* The maximum value the 16bit timer can contain. */
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#define timerMAX_COUNT                          0xffff
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/*-----------------------------------------------------------*/
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/*
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 * Measure the time between this interrupt and the previous interrupt to
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 * calculate the timing jitter.  Remember the maximum value the jitter has
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 * ever been calculated to be.
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 */
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static void prvCalculateAndStoreJitter( void );
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/*-----------------------------------------------------------*/
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/* The maximum time (in processor clocks) between two consecutive timer
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interrupts so far. */
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unsigned portSHORT usMaxJitter = 0;
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/*-----------------------------------------------------------*/
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void vSetupTimerTest( unsigned portSHORT usFrequencyHz )
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{
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        /* T2 is used to generate interrupts.  T4 is used to provide an accurate
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        time measurement. */
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        T2CON = 0;
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        T4CON = 0;
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        TMR2 = 0;
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        TMR4 = 0;
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        /* Timer 2 is going to interrupt at usFrequencyHz Hz. */
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        PR2 = ( unsigned portSHORT ) ( configCPU_CLOCK_HZ / ( unsigned portLONG ) usFrequencyHz );
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        /* Timer 4 is going to free run from minimum to maximum value. */
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        PR4 = ( unsigned portSHORT ) timerMAX_COUNT;
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        /* Setup timer 2 interrupt priority to be above the kernel priority so
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        the timer jitter is not effected by the kernel activity. */
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        IPC1bits.T2IP = configKERNEL_INTERRUPT_PRIORITY + 1;
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        /* Clear the interrupt as a starting condition. */
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        IFS0bits.T2IF = 0;
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        /* Enable the interrupt. */
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        IEC0bits.T2IE = 1;
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        /* Start both timers. */
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        T2CONbits.TON = 1;
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        T4CONbits.TON = 1;
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}
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/*-----------------------------------------------------------*/
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static void prvCalculateAndStoreJitter( void )
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{
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static unsigned portSHORT usLastCount = 0, usSettleCount = 0;
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unsigned portSHORT usThisCount, usDifference;
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        /* Capture the timer value as we enter the interrupt. */
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        usThisCount = TMR4;
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        if( usSettleCount >= timerSETTLE_TIME )
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        {
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                /* What is the difference between the timer value in this interrupt
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                and the value from the last interrupt. */
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                usDifference = usThisCount - usLastCount;
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                /* Store the difference in the timer values if it is larger than the
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                currently stored largest value.  The difference over and above the
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                expected difference will give the 'jitter' in the processing of these
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                interrupts. */
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                if( usDifference > usMaxJitter )
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                {
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                        usMaxJitter = usDifference;
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                }
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        }
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        else
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        {
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                /* Don't bother storing any values for the first couple of
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                interrupts. */
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                usSettleCount++;
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        }
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        /* Remember what the timer value was this time through, so we can calculate
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        the difference the next time through. */
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        usLastCount = usThisCount;
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}
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/*-----------------------------------------------------------*/
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void __attribute__((__interrupt__, auto_psv)) _T2Interrupt( void )
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{
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        /* Work out the time between this and the previous interrupt. */
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        prvCalculateAndStoreJitter();
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        /* Clear the timer interrupt. */
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        IFS0bits.T2IF = 0;
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}
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