ADC suddenly not working?

Arduino
#1

I am really at a loss here so I’m hoping someone can help.
Suddenly, when I’m working on my project the Seed isn’t reading my pots.
It seems to just be stuck at one value. I’ve moved the seed to a socket on a stripboard
with the same circuit and connections that worked fine on my breadboard,
but now nothing works. Not even when I put it back on my breadboard.

When I put the pot value on the serial monitor it just stays at 512 when I turn it.
I’m afraid I’ve fried the ADC, but I don’t see how that could happen. I haven’t connected anything external to it at all, just the same pots I used for my breadboard setup.

Can I reset the chip somehow?

#2

What voltage was on the top end of your pot ?

#3

The voltages varied between 3.22 and 3.18 on the pots.
So nothing that should burn the ADC.

#4

Agreed. There are actually 3 ADCs spread around about 16 inputs so maybe try a different input first, then one of the other 2 ADCs. Hopefully it’s a localised fault.

#5

Well this is maddening.
For some reason all the analog ins work now on the breadboard, but when I put the seed
in the socket of my circuit, the last two ins I need mess everything up.
Initially, if I hooked them up all my analog inputs showed 767. Now I’ve gotten it to where
the rest of the inputs work as they should with the pots but the last two still mess up.
I’ve changed the pots and moved them to other inputs but they still mess it up.
I’ll redo all the leads tomorrow.

#6

It’d be worth double checking the connection between your AGND and DGND pins as this would cause your ADC inputs to be intermittent or not work.

1 Like
#7

Well of course that was it…
I had a dodgy solder point on that wire which made the problem intermittent.
On the plus side I’m pretty much finished with the main part of the project now so I can
present it when I’ve got a bit of time to post it.

thanks a lot for your help!

#8

Of course! Its really easy to miss this because you’d still get GND continuity most places.

I’ve done a few bread-boardy things, and had some shoddy jumper wires cause very similar headaches. I’ve seen it enough now to recognize that most of the time, if everything but the controls are working it’s most likely that connection that’s botched somewhere.

Glad you got it sorted out!