TM4C1294NCPDT: TI-RTOS - Timestamp - How to setup clock source other than system clock?

Hi Abhijit,

After looking into this further, I realized that changing the TimeStampProvider will not change the timestamp's frequency.

In fact, SYSBIOS currently does not have support for doing so; therefore, the timestamp's source frequency will always be the same as the system clock (typically 120 MHz for TM4C).

However, I do have an alternative I can suggest.
You can implement your own timestamp provider inside your application using the ti/sysbios/family/arm/lm4/Timer.h module.

To do so, first add the following to your kernel configuration (*.cfg). This will statically create a kernel Timer instance.:

var Timer = xdc.useModule('ti.sysbios.family.arm.lm4.Timer');
var params = new Timer.Params;

/* Timer will run continuously */
params.runMode = Timer.RunMode_CONTINUOUS;

/* Timer will start automatically */
params.startMode = Timer.StartMode_AUTO;

/* Set the period to the max value */
params.period = 0xFFFFFFFF;
params.periodType = Timer.PeriodType_COUNTS;

/* For TM4C devices, this will be a 16 MHz tick source */
params.altclk = true;

/*
 * myTimerHandle will be a symbol globally accessible. Your application
 * just needs to include #include <xdc/cfg/global.h>
 * This handle can be used with any of the SYSBIOS timer APIs.
 */
Program.global.myTimerHandle = Timer.create(Timer.ANY, null, params);

Next, try using the simple example below in an application. It simply uses the timer created in the kernel configuration (*.cfg). The task sleeps for a second and then gets the current timer count.

/* XDC module Headers */
#include <xdc/std.h>
#include <xdc/runtime/System.h>

/* BIOS module Headers */
#include <ti/sysbios/BIOS.h>
#include <ti/sysbios/knl/Task.h>

#include <xdc/cfg/global.h>
#include <xdc/runtime/Types.h>
#include <ti/sysbios/family/arm/lm4/Timer.h>

#include <ti/drivers/Board.h>

Void task0Fxn(UArg arg0, UArg arg1);

Types_FreqHz freq;
Task_Struct task0Struct;
Task_Handle taskHandle;
Char taskStack[512];

/*
 *  ======== main ========
 */
int main()
{
    /* Construct BIOS Objects */
    Task_Params taskParams;

    /* Call driver init functions */
    Board_init();

    Task_Params_init(&taskParams);
    taskParams.stack = &taskStack;
    taskParams.stackSize = 512;
    Task_construct(&task0Struct, task0Fxn, &taskParams, NULL);

    /* Get the timer frequency. We expect freq.lo to return 16 MHz */
    Timer_getFreq(myTimerHandle, &freq);

    BIOS_start();    /* does not return */
    return(0);
}

Void task0Fxn(UArg arg0, UArg arg1)
{
    UInt count, timeSec, timeUsec, i = 0;

    while (1) {
        /*
         * Get the current timer ticks, this will return 0 if called before
         * BIOS_start(). This should be comparable to calling Timestamp_get32().
         */
        count = 0xFFFFFFFF - Timer_getCount(myTimerHandle);

        /* Calculate time elapsed since BIOS_start() */
        timeSec = count / freq.lo;
        timeUsec = count / (freq.lo / 1000000);

        System_printf("Timestamp[%d]: Sec %d\tuSec %d\n", i, timeSec, timeUsec);
        System_flush();

        i++;
        Task_sleep(1000);
    }
}

This can be used as a good starting point. One idea is to configure the timer to be periodic and increment a volatile counter in a timer callback. That way, your could always have uSecs, Secs, Hours, Days.....etc.

Derrick

Hello Derrick,

Thank your giving detailed response. Honestly speaking, at this time, I don't have time to try out your solution but will keep that in mind. Very sorry for that. However I got the message that we can't change timestamp provider source frequency. 

Once again thank you for taking time to respond to my query.

Regards

Abhijit