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

Rayman

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?

cgracey

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.

msrobots

you could use the smart pin feature of reading writing pins next to it without any jumpers...

Mike

Rayman

I think that would only work for digital signals...

Rayman

Oh, wait... There was something about inputting analog from neighboring pin...
I think that is what is getting removed from Rev.C...

Beau Schwabe

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.

Rayman

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...

cgracey

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.

Ariba

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.

Cluso99

IIRC the smartpins can read adjacent (digital?) pins 3-4 either side of the real pin (total of 7 plus its' own).