/*
	FreeRTOS.org V5.4.0 - Copyright (C) 2003-2009 Richard Barry.

	This file is part of the FreeRTOS.org distribution.

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	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
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	license and support terms are also available upon request.  See the 
	licensing section of http://www.FreeRTOS.org for full details.

	FreeRTOS.org 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
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	You should have received a copy of the GNU General Public License along
	with FreeRTOS.org; if not, write to the Free Software Foundation, Inc., 59
	Temple Place, Suite 330, Boston, MA  02111-1307  USA.


	***************************************************************************
	*                                                                         *
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	*                                                                         *
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	* explains numerous examples that are written using the FreeRTOS API.     *
	* Full source code for all the examples is provided in an accompanying    *
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	Please ensure to read the configuration and relevant port sections of the
	online documentation.

	http://www.FreeRTOS.org - Documentation, latest information, license and
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	http://www.SafeRTOS.com - A version that is certified for use in safety
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*/

/* 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;
}