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TMS570LS3137: TMDS570LS31HDK reads a different capture value than Oscilloscope.

Part Number: TMS570LS3137

Hi,

I am developing on TMDS570LS31HDK using IAR Embedded Workbench for ARM. I read the pwm with the "capGetSignal" command over the HET1[04] pin in HDK and get the frequency.
While reading a frequency value of 74.2 kHz from the same pin with an oscilloscope, capGetSignal returns 78.5 kHz when I examine it with debug.

What is the reason for this frequency difference? I am also sharing the Halcogen configurations that I have made below.


Software;

hetSIGNAL_t signalM;
float64 signalFrequency = 0.0F;

while(true)
{

    capGetSignal(hetRAM1, cap2, &signalM);
    
    signalFrequency = 1 / signalM.period;
}


  • Hi Cevdet,

    The HR share is enabled in your configuration, so the resolution of the PWM capture is 1 HR period (11.1ns). 

    Is the PWM signal generated by HET1? Is the input PWM signal clean?

    Please enable the suppression filter and set the preload value for the filter. This suppression filter can be used to filter out the unwanted pulse.