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CCS/TMS320F28379D: TMS320F28379D designDRIVE oscilloscope measurement

Min Zhang
Intellectual 450 points
Part Number: TMS320F28379D
Other Parts Discussed in Thread: DESIGNDRIVE

Tool/software: Code Composer Studio

I am try to debug the PWM code and watch it by using probe on the scope. I am pretty sure that the code is all right ( actually i am using the sample code provided by the TI ), i failed to watch it on the scope. It that because of the regular probe problem? I don't know if i need for a differential probe to measure the PWM signals. I try to connect the control ground and GPIO0 for the PWM1A, i see nothing. Anyone can give me a hand? thank you very much. 

min

  • 0
    TI__Genius 10845 points
    Hi Min,
    I think you will need differential probes to probe PWM signals. Also which board are you using? I guess you are probing the correct pin.

    Thanks
    Vasudha
  • 0 in reply to Vasudha Bhadoria
    Intellectual 450 points

    Hi Vasudha

    I use the TMS320F28379D board, which installed on the designDRIVE platform. I do look at the correct pin, basically for the EPWM1A , it is GPIO0. Also, i test on the PWM test point, i can see nothing by using regular probe as well. 

    thanks 

    Min

  • 0 in reply to Min Zhang
    TI__Guru 60865 points
    Hi Min,

    I'd probably break the problem into 2 parts:

    First, are you actually connecting to GPIO0 when you think you are? The easiest way to debug this is to set the GPIO mux to all '0's (GPIO mode) and set the GPIO direction to '1' (output). You can then toggle GPIO0 data register and see if you can see the corresponding state change on the scope input. You can do all of this pretty easily in the expressions window without any C code (do run through the initializations in one of the examples first though to get the system initialized).

    Once you confirm the pin hookups, then you can move onto checking that the ePWM is doing what you want. Some things to examine:
    Is the GPIO mux correct to put ePWM1A on GPIO0? Is the timer actually counting? Are the compare values/events configured to cause a state change on the pin? etc.
  • 0 in reply to Devin Cottier
    Intellectual 450 points
    I use the TI sample code for the 28377D, initialPWM1GPIO function was did by function, disable pull-up and open MUX (1), it definitely no problem, i try with differential probe, still no PWM output, i use the test-point PWM1A for the red, with control ground black, see nothing even by using TI sample code. Do you think i may damage the device with regular probe ? I try connect regular probe with one side test point and one side ground, the board is floating and oscilloscope is connect to ground, i just do that without clear thinking .
  • 0 in reply to Min Zhang
    TI__Guru 60865 points
    Hi Min,

    I think you should be OK. Also, regular scope probe should probably be OK...just connect probe input to GPIO0 and probe ground to board ground.

    Are you able to see toggling on this pin by setting the GPIO to GPIO output mode (not ePWM mode) and then manually (or using code) toggle the GPIO data registers?
  • 0 in reply to Devin Cottier
    TI__Genius 10845 points
    Hi Min,

    Let us know if you were able to resolve the issue.

    Thanks
    Vasudha