Demo/CORTEX_LM3Sxxxx_Eclipse/RTOSDemo/timertest.c

/*
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	of http://www.FreeRTOS.org for full details.


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	Please ensure to read the configuration and relevant port sections of the
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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"

/* 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		( * ( ( unsigned long * ) ( TIMER1_BASE + 0x48 ) ) )

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

/* 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;
}