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TM4C123GH6PGE: Parallel GPIO Operation

Prodigy 10 points

Replies: 1

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Part Number: TM4C123GH6PGE

Hi,

In my project, we are going to use 2 mcu. One is main mcu, the other is backup mcu. Now these two units have the same job. when first boot backup mcu is triggered to sleep mode by main mcu.

The main question is : These two mcus are connected as parallel. And I do not know how gpio pins react at this connection? I haven't test it yet, but if add diode for all gpio pins can i use these two mcu's gpio for the same job? I mean, does this diode connection provide me a safe operation field while one mcu is running and the other one is sleeping?

If the above idea will fail, can you suggest me any application note or something for this parallel connection topology?

Best regard.

Görkem Mert KESKİN

1 Reply

  • Hello Görkem,

    So I can't say that I have heard of anyone doing that before though I get the concept here.

    In general the issue you'd run into with that setup is when pins that are tied together are then both configured as outputs. If that occurs, you would get a clash where one output is trying to drive current into the other or both are trying to drive current at once. That's the big thing you would want to avoid as that could damage the device.

    That said, my first thought is that if one MCU is always asleep, then the question about diodes and such would be more to possibly save on system power by not injecting voltages into the powered down MCU. However, if there are times they would both be up or you want to be certain an error in operation doesn't have both up accidentally together, then the diodes could work in theory... but the one caveat is that you'd need to be sure the voltage drop isn't going to impact the other devices on the system. Going from 3.3V to 2.6V could lower the voltage beyond the minimum voltage threshold for some devices.

    Since the issue is really related to how the outputs could drive each other, the diodes would only be needed for pins that will output signals.

    Do those details help clarify how the I/O would work for you well enough?

    Best Regards,

    Ralph Jacobi

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