/*
	FreeRTOS.org V5.2.0 - Copyright (C) 2003-2009 Richard Barry.

	This file is part of the FreeRTOS.org distribution.

	FreeRTOS.org 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.

	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 
	more details.

	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.

	A special exception to the GPL is included to allow you to distribute a 
	combined work that includes FreeRTOS.org without being obliged to provide
	the source code for any proprietary components.  See the licensing section
	of http://www.FreeRTOS.org for full details.


	***************************************************************************
	*                                                                         *
	* Get the FreeRTOS eBook!  See http://www.FreeRTOS.org/Documentation      *
	*                                                                         *
	* This is a concise, step by step, 'hands on' guide that describes both   *
	* general multitasking concepts and FreeRTOS specifics. It presents and   *
	* explains numerous examples that are written using the FreeRTOS API.     *
	* Full source code for all the examples is provided in an accompanying    *
	* .zip file.                                                              *
	*                                                                         *
	***************************************************************************

	1 tab == 4 spaces!

	Please ensure to read the configuration and relevant port sections of the
	online documentation.

	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"

/* 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;
}