Aaron,

 

“Real Time Clock” of the SDK has resolution of 1msec (you can verify this by calling clock_getres() function). If you look at your numbers in decimal format, you have to ignore everything below msec resolution:

 

Idx  Value
  0  0x0EE6B9D8 -> 250,000,880 -> 250 msec
  1  0x0EE7AE23 -> 250,064,419 -> 250 msec
  2  0x0EE7A26E -> 250,061,422 -> 250 msec
...
15  0x0EE70A3D -> 250,022,461 -> 250 msec
16  0x0EE6FE88 -> 250,019,464 -> 250 msec
17  0x0EE6F2D3 -> 250,016,467 -> 250 msec
...
198  0x0EE7ABDA -> 250,063,834 -> 250 msec
199  0x0EE7A025 -> 250,060,837 -> 250 msec

 

If you would run your code for over msec, you will see that 250 msec value will change to 251 msec.

 

In other words, API provides for 1 nsec resolution, but “Real Time Clock” implementation has resolution of 1 msec, so the user should not expect to have any meaningful data in msec and nsec portion of the tv_nsec member.

 

Leonard N. Elevich

Motorola DSPO

 

-----Original Message-----
From: Aaron Needles [mailto:a...@tde.alstom.com]
Sent: Wednesday, October 09, 2002 8:47 AM
To: m...@yahoogroups.com
Subject: [motoroladsp] Use of clock_gettime() on DSP56F807

 

Hi,
    I'm attempting to use the "Real Time Clock" feature in Motorola's
DSP but am getting inconsistent time values returned when I call
clock_gettime() successively.

The code below was added to a project created with "Embedded SDK
Stationary" and only the INCLUDE_TIMER #define added to appconfig.h.
When I run the code on our DSP56F807EVM via External RAM and then
display timeBuf[] as variable with value as hexadecimal, I get the
following (summarized)...

Idx  Value
  0  0x0EE6B9D8
  1  0x0EE7AE23
  2  0x0EE7A26E
...
15  0x0EE70A3D
16  0x0EE6FE88
17  0x0EE6F2D3
...
198  0x0EE7ABDA
199  0x0EE7A025

I was expecting a smoothly increasing integer count representing time
elapsed in nanoseconds. Has someone used the clock_gettime() function
sucessfully? I am using current versions of CodeWarrior+patch and
Motorola's SDK (2.5)

Thanks in advance,
    Aaron

Aaron Needles
Senior Software Engineer
Alstom Schilling Robotics
a...@tde.alstom.com /* File: main.c */

#include "timer.h"

/*******************************************************
* Skeleton C main program for use with Embedded SDK
*******************************************************/

#define NUM_ITERATIONS 200
unsigned long timeBuf[NUM_ITERATIONS];

void main (void)
{
    int i;
    struct timespec thisTime;
    struct timespec timeDelay = {0, 250000000}; // 1/4 sec

    // This is an attempt to allow the clock to synchronize/stabalize.
    // I don't believe it makes any difference.
    nanosleep(&timeDelay, NULL);

    // Just in case...
    for (i=0; i<NUM_ITERATIONS; i++) {
        timeBuf[i] = 0;
    }

    for (i=0; i<NUM_ITERATIONS; i++) {
        archDisableInt();
        clock_gettime(CLOCK_REALTIME, &thisTime);
        asm(nop);
        asm(nop);
        asm(nop);
        asm(nop);
        asm(nop);
        asm(nop);
        asm(nop);

        // Save time
        timeBuf[i] = thisTime.tv_nsec;
        archEnableInt();
    }

    while (1) {
// Set breakpoint on asm(nop). Read timeBuf[] values after break
        asm(nop);
    }     
      return;          /* C statements */
}

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