timertest.c

这个Demo程序是应用在FreeRTOS上的Demo

/*
	FreeRTOS.org V5.0.2 - Copyright (C) 2003-2008 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 as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	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 can be applied should you wish 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 of how and when the exception
	can be applied.

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	Please ensure to read the configuration and relevant port sections of the
	online documentation.

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*/

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


/* Scheduler includes. */
#include "FreeRTOS.h"

/* The maximum value the 16bit timer can contain. */
#define timerMAX_COUNT				0xffff

/* The timer 2 interrupt handler. */
void __attribute__( (interrupt(ipl0), vector(_TIMER_2_VECTOR))) vT2InterruptWrapper( void );

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

/* Incremented every 20,000 interrupts, so should count in seconds. */
unsigned portLONG ulHighFrequencyTimerInterrupts = 0;

/* The frequency at which the timer is interrupting. */
static unsigned portLONG ulFrequencyHz;

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

void vSetupTimerTest( unsigned portSHORT usFrequencyHz )
{
	/* Remember the frequency so it can be used from the ISR. */
	ulFrequencyHz = ( unsigned portLONG ) usFrequencyHz;

	/* T2 is used to generate interrupts above the kernel and max syscall interrupt
	priority. */
	T2CON = 0;
	TMR2 = 0;

	/* Timer 2 is going to interrupt at usFrequencyHz Hz. */
	PR2 = ( unsigned portSHORT ) ( ( configPERIPHERAL_CLOCK_HZ / ( unsigned portLONG ) usFrequencyHz ) - 1 );

	/* Setup timer 2 interrupt priority to be above the kernel priority so 
	the timer jitter is not effected by the kernel activity. */
	ConfigIntTimer2( T2_INT_ON | ( configMAX_SYSCALL_INTERRUPT_PRIORITY + 1 ) );

	/* Clear the interrupt as a starting condition. */
	IFS0bits.T2IF = 0;

	/* Enable the interrupt. */
	IEC0bits.T2IE = 1;

	/* Start the timer. */
	T2CONbits.TON = 1;
}
/*-----------------------------------------------------------*/

void vT2InterruptHandler( void )
{
static unsigned portLONG ulCalls = 0;

	++ulCalls;
	if( ulCalls >= ulFrequencyHz )
	{
		/* Increment the count that will be shown on the LCD. 
		The increment occurs once every 20,000 interrupts so
		ulHighFrequencyTimerInterrupts should count in seconds. */
		ulHighFrequencyTimerInterrupts++;
		ulCalls = 0;
	}

	/* Clear the timer interrupt. */
	IFS0bits.T2IF = 0;
}