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/*

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

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

    *                                                                         *

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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.

    http://www.OpenRTOS.com - Commercial support, development, porting,

    licensing and training services.

*/

/* High speed timer test as described in main.c. */

/* Scheduler includes. */

#include "FreeRTOS.h"

/* Library includes. */

#include "hw_ints.h"

#include "hw_memmap.h"

#include "hw_types.h"

#include "interrupt.h"

#include "sysctl.h"

#include "lmi_timer.h"

#include "hw_timer.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  ( configCPU_CLOCK_HZ / timerINTERRUPT_FREQUENCY )

/* The highest available interrupt priority. */

#define timerHIGHEST_PRIORITY                   ( 0 )

/* Misc defines. */

#define timerMAX_32BIT_VALUE                    ( 0xffffffffUL )

#define timerTIMER_1_COUNT_VALUE                ( * ( ( volatile unsigned long * ) ( ( unsigned portLONG ) TIMER1_BASE + 0x48UL ) ) )

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

/* Interrupt handler in which the jitter is measured. */

void Timer0IntHandler( void );

/* Stores the value of the maximum recorded jitter between interrupts. */

volatile unsigned portLONG ulMaxJitter = 0;

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

void vSetupHighFrequencyTimer( void )

{

unsigned long ulFrequency;

        /* Timer zero is used to generate the interrupts, and timer 1 is used

        to measure the jitter. */

        SysCtlPeripheralEnable( SYSCTL_PERIPH_TIMER0 );

    SysCtlPeripheralEnable( SYSCTL_PERIPH_TIMER1 );

    TimerConfigure( TIMER0_BASE, TIMER_CFG_32_BIT_PER );

    TimerConfigure( TIMER1_BASE, TIMER_CFG_32_BIT_PER );

        /* Set the timer interrupt to be above the kernel - highest. */

        IntPrioritySet( INT_TIMER0A, timerHIGHEST_PRIORITY );

        /* Just used to measure time. */

    TimerLoadSet(TIMER1_BASE, TIMER_A, timerMAX_32BIT_VALUE );

        /* Ensure interrupts do not start until the scheduler is running. */

        portDISABLE_INTERRUPTS();

        /* The rate at which the timer will interrupt. */

        ulFrequency = configCPU_CLOCK_HZ / timerINTERRUPT_FREQUENCY;

    TimerLoadSet( TIMER0_BASE, TIMER_A, ulFrequency );

    IntEnable( INT_TIMER0A );

    TimerIntEnable( TIMER0_BASE, TIMER_TIMA_TIMEOUT );

        /* Enable both timers. */

    TimerEnable( TIMER0_BASE, TIMER_A );

    TimerEnable( TIMER1_BASE, TIMER_A );

}

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

void Timer0IntHandler( void )

{

unsigned portLONG ulDifference;

volatile unsigned portLONG ulCurrentCount;

static unsigned portLONG ulMaxDifference = 0, ulLastCount = 0;

        /* We use the timer 1 counter value to measure the clock cycles between

        the timer 0 interrupts. */

        ulCurrentCount = timerTIMER_1_COUNT_VALUE;

        TimerIntClear( TIMER0_BASE, TIMER_TIMA_TIMEOUT );

        if( ulCurrentCount < ulLastCount )

        {

                /* How many times has timer 1 counted since the last interrupt? */

                ulDifference =  ulLastCount - ulCurrentCount;

                /* Is this the largest difference we have measured yet? */

                if( ulDifference > ulMaxDifference )

                {

                        ulMaxDifference = ulDifference;

                        ulMaxJitter = ulMaxDifference - timerEXPECTED_DIFFERENCE_VALUE;

                }

        }

        ulLastCount = ulCurrentCount;

}