CCS/TMS320F28335: How can I measure the elapsed time between each loop?

Hi Ata,

For measuring elapsed time within your code and using these times within your program, CPU timer and eCap are your two options.

1) CPU Timer:

You're correct, you will not be using interrupts for this method. If you're going off of the CPU Timer example from ControlSuite or C2000ware you can remove anything related to interrupts ("InitPieCtrl();", "InitPieVectTable();", etc.). You will initialize and configure your CPU Timer, I suggest making the period the largest possible (0xFFFFFFFF). Then Reset/Start the timer at the beginning of the code portion you want to measure, save the initial CPU timer value to a variable, then after the program portion save the CPU timer value to another variable. The difference of these values will be your elapsed time in clock cycles (You will have to convert if you want seconds/minutes). I'll provide an example below...

void StartTimer(void)
{
    cpuTime1 = 0;

    EALLOW;
    CpuTimer2Regs.TCR.bit.TRB = 1;        // Reset CPU timer to period value
    CpuTimer2Regs.TCR.bit.TSS = 0;        // Start or reset CPU timer 2
    cpuTime1 = CpuTimer2Regs.TIM.all;     // Get value of CPU Timer 2 before code
    EDIS;
}

void StopTimer(void)
{
    EALLOW;
    cpuTime2 = CpuTimer2Regs.TIM.all;    // Get value of CPU Timer 2 after code
    cpuTime = cpuTime1 - cpuTime2;     // Calculate time using cpuTimer2
    CpuTimer2Regs.TCR.bit.TSS = 1;        // Start or reset CPU timer 2
    EDIS;
}

2) eCap:

The eCap method works similar to measuring a pulse width using an oscilloscope. So for your case, it's like setting a GPIO pin high when the code portion starts and returning it to low after the code finishes, and then measuring the pulse width for the elapsed time. You would send the output pin you're setting high to an eCap input pin on your board to accomplish this. I believe the ecap_capture_pwm example in ControlSuite would be a good place to start if you want to use this method.

Example below...

GpioDataRegs.GPADAT.bit.GPIO1 = 1;    // Start timing, Ecap
// Code to be timed here...
GpioDataRegs.GPADAT.bit.GPIO1 = 0;   // Stop timing, Ecap
ecap_time = ECap1Regs.CAP2;          // Calculate time using ECap2 (will be in clock cycles)

You can save any of these registers to a variable, i suggest they be Uint32. Both of these methods will give you nearly the same timing.

Hope this helps, let me know if you have any further questions.

Best,

Kevin

Ata,

That looks pretty close. The only thing I think you need to do is make cpuTime1, cpuTime2, and cpuTime global variables.

You can test your code just by running a for loop that counts up in place of "//my code".

int i = 0;

for(i=0; i < 90000; i++){}

Hope it works for you,
Kevin