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MSP432E401Y: Driving 3.3V into a GPIO that is setup as an output

Stephen Depot
Prodigy 10 points
Part Number: MSP432E401Y

I need to use test points to apply external 3.3V to stimulate HW on my board.  That signal is normally controlled by a GPIO setup as an output on the MSP432.  But unfortunately I do not have control over the output for this test.  So the question I have is: can I apply the external 3.3V to the test point without damaging the MSP432's GPIO configured as an output?  There is no concern of driving too high of voltage.  During the test, the MSP432 will not have control over the pin.  I saw in the datasheet that all GPIOs are High Z by default, but not sure exactly how that applies in this situation with an assigned pin.

This is the way it has to be done due to the particular constraints on our design, so suggestions of doing it other ways is not what I am looking for.  Just simply wondering if doing what is mentioned above is ok or will cause damage.

  • 0
    TI__Guru**** 191886 points
    Stephen Depot said:
    I saw in the datasheet that all GPIOs are High Z by default,

    When the GPIOs are in high Z it means they are in input state. You can externally drive voltage on the test point. However, if the GPIO pin is already in output state, you should drive a conflicting state on the testpoint. For example, if the GPIO is driving a steady state low and you try to force a high on the testpoint. The voltage on the signal may be in an indeterministic state where it will not meet the Vih and Vil of the receiving component. 

  • 0 in reply to Charles Tsai
    Prodigy 10 points

    Ahh ok that makes sense.  So, if I were able to setup that GPIO as an input and simply ignore it (from the MSP432's perspective) would that result in valid voltage levels on the line?  That option may very well be possible for my application if it will work.  As long as the source of the 3.3V can deliver enough current for the receiving component, as well as the MSP432's now input pin.