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Problem Input TMS320F28335

FloSwingS
Prodigy 30 points

Other Parts Discussed in Thread: TMS320F28335

Hi everybody !

I'm working on the dsp card (TMS320F28335) and I've problem with the input of this dsp. In fact, I want to use an input to detect a high state, however, with pullup resistors, the input is already high (So I can't detect the high state). So I disabled by the soft the pullup resistors but now another problem appears, I detect the high state (optocoupler delivering the 3v ofthis input), but the low state, I did not 0V, the voltage is not stable (roughly it varies from 0 to 3V). I wonder if you have a solution that allows me to ensure 0V to 3V (low state and high state) ??? only by soft programming (not pulldown...)

Thank you in advance.

  • 0
    Expert 1150 points

    It looks like you have a floating input. There is no software solution for this, better use pulldown. In case it's impossible you can try configure your input as output and force it low for a short time immediately before you going to detect a hight state to discharge parasitic capacitance but I not sure it will work.

  • 0 in reply to Roman Ermakov
    Prodigy 30 points

    Ok Roman, I thank you for your answer. I was hoping this is a mistake on my part (programming error) and change a value in a register to stabilize the input. I will continue to seek and try with pulldown resistors to force the low state to 0V.