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MSP432P401R: Code failing to run when MSP432 powered externally

Nicholas Kimball91
Prodigy 210 points

Part Number: MSP432P401R

Today, all of a sudden, my MSP432 would not run its program without the Launchpad being plugged into the computer. Previously, I was always able to power it externally without any power from the debugger side of the Launchpad and the code would run perfectly. However, the MSP432 now waits in some sort of halted state until I plug the USB cable that runs from the debug side of the board into my computer. As I am not powering it through the debug side, I do not think this is a power issue. In addition, once the code starts after plugging the USB cable in, I can unplug the USB cable and the code will continue to run.

I have removed the 3V3 and 5V jumper pins from the debugger to the MSP432 side as I am powering the MPS432 from an eternal source. However, the debugger pins are still connected. It seems like the MSP432 is waiting in a halted state until it gets some sort of signal from the debugger. Is this possible?

  • 0
    TI__Expert 8510 points
    Nicholas,
    I don't think it's likely that your program is waiting on the debugger, but perhaps it is hanging waiting on another input? A couple of questions come to mind
    1. What program are you running and what resources (EUSCI/UART, SPI, etc)
    2. Does the LaunchPad behave the same way in terms of hanging if you try to run one of the standard examples.
    - If the code you're trying to run isn't one of the standard examples currently, I would suggest trying to pull an example that uses the same resources that your programe does, and see if you still see the program hang.

    Hope this helps. I look forward to your reply.

    Regards,
    Bob Landers
  • 0 in reply to Bob Landers
    Prodigy 210 points

    Hi Bob,

    I actually figured it out. When I unplugged the header which was connecting the RSTn line into the MSP, the program started to run. Somehow, even when the debug chip is off, the RSTn line is being pulled down. The code also ran when I unplugged the GND pin from the debug side to the MSP side. It seems like the RSTn node is somehow being pulled low even though I couldn't find a pull-down resistor on the Launchpad schematic.

  • 0 in reply to Nicholas Kimball91
    TI__Expert 8510 points
    OK. Thanks for following up with your findings. I think since you weren't providing power via the USB/ET110 side, the XDS_RESET was pulling low, and that connection in turn pulled your RSTn line low into the MCU. Once you fully disconnected the debugger interface, then the MCU-side RSTn line had nothing pulling down, and that's why the program starting working at that point.

    Note- all it would take for this to happen is that some leakage path to GND exists on the RSTn line. The pullup resistor is fairly high impedance, so it wouldn't take much current leakage to pull down the line.
    Regards,
    Bob Landers

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