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/*

    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.

    ***************************************************************************

    *                                                                         *

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    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *

    *                  http://www.FreeRTOS.org/Documentation                  *

    *                                                                         *

    * A pdf reference manual is also available.  Both are usually delivered   *

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    * and 8pm GMT (although please allow up to 24 hours in case of            *

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    ***************************************************************************

    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 exception 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!

    http://www.FreeRTOS.org - Documentation, latest information, license and

    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety

    critical systems.

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    licensing and training services.

*/

/*

 * 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. */

void vTimer2_ISR_Handler( void ) __attribute__((interrupt));

/* 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;

}

/*-----------------------------------------------------------*/

void vTimer2_ISR_Handler( void )

{

volatile unsigned short usCurrentCount;

static unsigned short usMaxCount = 0;

static unsigned long ulErrorCount = 0UL;

        /* This is the highest priority interrupt in the system, so there is no

        advantage to re-enabling interrupts here.

        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;

        portNOP();

        portNOP();

        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;

}