main.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <stdint.h>


#define DEFAULT_DELAY   1

uint32_t m_nStart;               //DEBUG Stopwatch start cycle counter value
uint32_t m_nStop;   //DEBUG Stopwatch stop cycle counter value
#define DEMCR_TRCENA    0x01000000

/* Core Debug registers */
#define DEMCR           (*((volatile uint32_t *)0xE000EDFC))
#define DWT_CTRL        (*(volatile uint32_t *)0xE0001000)
#define CYCCNTENA       (1<<0)
#define DWT_CYCCNT      ((volatile uint32_t *)0xE0001004)
#define CPU_CYCLES      *DWT_CYCCNT



#define STOPWATCH_START { m_nStart = CPU_CYCLES; }/*DWT_CYCCNT;}*/
#define STOPWATCH_STOP  { m_nStop = CPU_CYCLES; }




static inline void stopwatch_reset(void)
{
    /* Enable DWT */
    DEMCR |= DEMCR_TRCENA;
    *DWT_CYCCNT = 0;
    /* Enable CPU cycle counter */
    DWT_CTRL |= CYCCNTENA;
}

static inline uint32_t stopwatch_getticks()
{
    return CPU_CYCLES;
}

static inline void stopwatch_delay(uint32_t ticks)
{
    stopwatch_reset();
    while(1)
    {
            if (stopwatch_getticks() >= ticks)
                    break;
    }
}

uint32_t CalcNanosecondsFromStopwatch(uint32_t nStart, uint32_t nStop)
{
    uint32_t nTemp;
    uint32_t n;
    uint32_t SystemCoreClock = 180000000;
    nTemp = nStop - nStart;

    nTemp *= 1000;                          // Scale cycles by 1000.
    n = SystemCoreClock / 1000000;          // Convert Hz to MHz. SystemCoreClock = 168000000
    nTemp = nTemp / n;                      // nanosec = (Cycles * 1000) / (Cycles/microsec)

    return nTemp;
}



int main( int argc, char **argv )
{
        int     btn; //User Button status
        int     ld = 1; /*LED value*/
        long int diff;
        int     delay = DEFAULT_DELAY;  // Initial value for the delay

        int timeDiff = 0;


    STOPWATCH_START;
    printf("Try...\n\n");
    STOPWATCH_STOP;
    timeDiff = CalcNanosecondsFromStopwatch(m_nStart, m_nStop);
    printf("My function took %d nanoseconds\n", timeDiff);


        return( 0 );
}