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Safe to tie two (or three) P2 I/O pins together? — Parallax Forums

Safe to tie two (or three) P2 I/O pins together?

RaymanRayman Posts: 13,855
edited 2020-01-23 17:26 in Propeller 2
For testing out various ADC/DAC modes, seems like it'd be convenient to just jumper two P2 I/O pins together.
Is this safe?
I'm pretty sure I've had P1 pins shorted together and not break them (probably more than once).
I'm tempted to try it, but also afraid :)

Will you fry the pins/chip if one pin is driving high and the other is driving low?

Comments

  • cgraceycgracey Posts: 14,133
    It's fine. If you cause them to drive against each other, it would cause some power dissipation, of course. If it's a bunch of DACs outputting the same value, no extra power will be dissipated. ADC pins can be ganged together, too, but be careful at the higher magnifications, because their offsets will be different, causing their readings to pull from their individual centers.
  • msrobotsmsrobots Posts: 3,704
    you could use the smart pin feature of reading writing pins next to it without any jumpers...

    Mike
  • RaymanRayman Posts: 13,855
    I think that would only work for digital signals...
  • RaymanRayman Posts: 13,855
    Oh, wait... There was something about inputting analog from neighboring pin...
    I think that is what is getting removed from Rev.C...
  • Beau SchwabeBeau Schwabe Posts: 6,547
    As mentioned above, yes it will probably work just fine, BUT In efforts to promote safe design habits you should just buffer it with something that can adequately provide the current requirement you desire.
  • RaymanRayman Posts: 13,855
    I'm just looking to make one an output and the other an input. But, wanted to know I'm safe in case I make a mistake...
  • cgraceycgracey Posts: 14,133
    Rayman wrote: »
    I'm just looking to make one an output and the other an input. But, wanted to know I'm safe in case I make a mistake...

    You are safe. I do it all the time.
  • AribaAriba Posts: 2,682
    Good to know.
    I have made a custom P2 board which brings not all P2 pins to headers, so I just connected a few header pins to two P2 pins to be able to run some code and look at the output with a parallel running cog in scope mode.
  • Cluso99Cluso99 Posts: 18,069
    IIRC the smartpins can read adjacent (digital?) pins 3-4 either side of the real pin (total of 7 plus its' own).
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