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Problems generating PWM on eZdsp F28335

Filippo Cona
Intellectual 450 points

Other Parts Discussed in Thread: CONTROLSUITE

Hi there,

I'm using the eZdsp F28335 and the example project ecap_capture_pwm from the controlSUITE collection (device_support\f2833x\v133\DSP2833x_examples_ccsv4\ecap_capture_pwm).

My problem is that I don't see the PWM on GPIO4 (pin13 on connector P8) and consequently the ECap interrupt is not generated. More specifically, The PWM signal is always at high level if I connect GPIO4 to the Ecap pin, GPIO24 (pin 33 on connector 33), while it is always at low level if cut the connection between the two pins. I'm using pin 39 on connector P8 as ground, but nothing changes if I use any of the other GNDs defined on the eZdsp datasheet.

I was wondering if I missed something configuring the HW (switches, jumpers and so on), or if there is a known issue about this example. For the HW configuration, SW1 is set for jump to SARAM, and actually the code runs, I can debug it; all the JP# are in the same position as shipped from factory.

I don't know if it can be a useful information, but I'm using the XDS200 as JTAG connector.

I thank you in advance for your support,

Filippo

  • 0
    Guru 192875 points
    Hi Filippo,

    Refer to this example: C:\ti\controlSUITE\device_support\f2833x\v141\DSP2833x_examples_ccsv5\ecap_apwm
    The one that you're referring to : is to capture PWM signal and get the capture counts and not to generate.

    Regards,
    Gautam
  • 0 in reply to Gautam Iyer
    Intellectual 450 points

    Hi Gautam, thanks for the quick reply!

    I'll try the other example, but nonetheless I do not understand why I would not see the PWM signal with the example I'm using right now. I mean, in the assumptions of the main .c file it is asked to "Make the following external connection: EPWM3 on GPIO4 should be connected to ECAP1 on GPIO24.", so it seemed to me that the example should generate a PWM signal whose period changes each time the ecap module gets a given set of edges in the PWM signal.

    What am I misunderstanding?

  • 0 in reply to Filippo Cona
    Guru 192875 points

    Filippo Cona said:
    "Make the following external connection: EPWM3 on GPIO4 should be connected to ECAP1 on GPIO24.", so it seemed to me that the example should generate a PWM signal whose period changes each time the ecap module gets a given set of edges in the PWM signal.

    Yes, that should be the ideal case but is not here.

    Filippo Cona said:
    What am I misunderstanding?

    If you check the ePWM configuration in the example code, it does not have action events at all.  Hence no PWM output but just the timer.

    Do check the example code that I've asked you to refer. You'll surely observe the PWM wave.

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Intellectual 450 points

    Hi Gautam,

    I just made a monstrous hybrid between the two examples, so that now I generate the PWM with ecap2 (following the example you suggested) and I monitor its edges with ecap1 (following the example I started from) and everything works as expected: times reported from ecap 1 capture registers perfectly resemble the period of the square wave I see on the oscilloscope.

    I'm still a bit concerned as to why I cannot generate the PWM signal using the PWM module, but I'll investigate this issue another time.

    Thanks a lot for your support!

    Best regards,

    Filippo

  • 0 in reply to Filippo Cona
    Guru 192875 points
    You're Welcome!

    Goodluck & Regards,
    Gautam