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Original question:

TMS320F280049C: GPIOs pulled up when start up or reset

TMS320F280037: Unwanted pull-up when programming device & launching debug

Chris Wilkinson
Prodigy 40 points
Part Number: TMS320F280037


(not 49C, sorry.)

(80-pin QFP, package PN)

Hi, my microcontroller is pulling up pin 64 (GPIO40/PWM2B) when I launch a debug session in CCS 12.4.0.00007.  The application is a switching power converter, and this pull-up has caused power FET damage.  Can anyone suggest what might be causing this?  Note that the pull-up doesn't activate at all on POR.  I don't currently know how to control any aspect of the debug-session-launching process.

For this scope image, each pin shown has a 10kΩ external pull-down and nothing else connected

This next scope image shows the internal pull-up pulses without the external 10kΩ pull-downs, so all 4 pins are completely open except for the probes.  (And this image is noisier due to suboptimal probe configuration.)

As a final note, the 1st pulse doesn't occur when I reload the program during a debug session by building and then clicking "yes" to "A file that you are debugging has been modified.  Do you want to reload it?"  This last image shows that, with the external 10k pull-downs present.

Thanks,

Chris

  • 0
    TI__Mastermind 30185 points

    Hello Chris,

    1. Per the post you referenced here, have you verified that the pins were at no point damaged such as by over-current/voltage?
    2. How many devices is this occurring on?
    3. Are these pins connected to any other hardware?
    4. Is this pull-up issue happening on all GPIOs or just the ones you've mentioned here?
    5. Would it be possible to verify this pull-up behavior on the device when it is removed from your system?
  • 0 in reply to Omer Amir
    Prodigy 40 points

    Hi Omer,

    1. No overvoltage or overcurrent damage.  Note above that the pins work correctly once the user program starts.
    2. It is occurring identically on 2 out of 2 devices (one in-system, and a different one on an isolated control board).
    3. In the above pictures, no other hardware but the 10k pull-down and the differential probe.
    4. I've only seen it on GPIO40/EPWM2B. I've only checked the four outputs of EPWM1 and EPWM2, not all the GPIOS.
    5. I don't have a convenient way to test the microcontroller outside of the control PCB. I could set something up if I find any limitations to my current workaround, which is discharging some things before programming or launching debug.

  • 0 in reply to Chris Wilkinson
    TI__Guru* 95315 points
    Chris Wilkinson said:
    For this scope image, each pin shown has a 10kΩ external pull-down and nothing else connected

    In the above line, you say there is an external pull-down.

    Chris Wilkinson said:
    This scope image shows the pull-up pulses without the 10kΩ pull-ups,

    In the above line, you talk about external pull-ups. Which is correct?

    Glitching was seen on some older C2000 MCUs when proper power-sequencing was not followed (during power-up). However, you are saying no glitches are observed during power-up and that a glitch is seen (that too in only one pin) only when code is loaded.

  • 0 in reply to Hareesh Janakiraman
    Prodigy 40 points

    External pull-down is correct.  I will edit my original post to fix that.

    Hareesh Janakiraman said:
    Glitching was seen on some older C2000 MCUs when proper power-sequencing was not followed (during power-up). However, you are saying no glitches are observed during power-up and that a glitch is seen (that too in only one pin) only when code is loaded.

    That is correct.

  • 0 in reply to Chris Wilkinson
    TI__Guru* 95315 points

    Chris,

              Could you please examine your gel files? Did you modify any gel file? Can you please send a scope-shot of this GPIO pin when you power the board? Please capture 1.2v, 3.3v, -XRS and GPIO40 as the supplies ramp.