user7158: I have a prototyping shield for an Arduino Uno. I accidentally plugged the shield into my arduino so that the pins were all "off by one". I didn't think this was possible, but it turns out that the extra pin just slips between the gaps in the pin headers:

I powered it on not realising. The arduino didn't show any LEDs, so I powered it down, saw my mistake, and plugged it all in again.
Now though A0-A5 are all reading high values (~900-1000 when I do analogRead(A0)), even when I have pulldown resistors on them, and they still read like that when I unplug my shield all together.
The digital writes all work perfectly.
I'm thinking that I've broken the Arduino. Is that possible, or could it be something else?

user6959: There is not (yet) enough information to be certain, but it seems likely that you have damaged the Arduino.
If damage has occurred it's more likely to have been caused by what happened on the other side of the board, where pins carry power supply voltages. You do not say what your power source is or where it is connected (USB, 5V in, Vin, ...) but I'd guesstimate that the connection of UNO 5V to Shield 3V3 allowed back feed into the UNO by any of a number of possible paths. UNO Vin connects to shield ground and a second UNO ground connects to a second UNO ground - so if the UNO was powered via Vin you'd expect the power supply to have been shorted. This might damage some power supplies but usually not. 
Can you please advise what voltage was connected and to what pin. And do shield pins all offset by 1 on the other side, as I've shown?


7158: <p>I have a prototyping shield for an Arduino Uno. I accidentally plugged the shield into my arduino so that the pins were all "off by one". I didn't think this was possible, but it turns out that the extra pin just slips between the gaps in the pin headers:</p>

<p><img src="https://i.stack.imgur.com/gfEkK.jpg" alt="enter image description here"></p>

<p>I powered it on not realising. The arduino didn't show any LEDs, so I powered it down, saw my mistake, and plugged it all in again.</p>

<p>Now though A0-A5 are all reading high values (~900-1000 when I do <code>analogRead(A0)</code>), even when I have pulldown resistors on them, and they still read like that when I unplug my shield all together.</p>

<p>The digital writes all work perfectly.</p>

<p>I'm thinking that I've broken the Arduino. Is that possible, or could it be something else?</p>
 6959: <p>There is not (yet) enough information to be certain, but it seems likely that you have damaged the Arduino.</p>

<p>If damage has occurred it's more likely to have been caused by what happened on the other side of the board, where pins carry power supply voltages. You do not say what your power source is or where it is connected (USB, 5V in, Vin, ...) but I'd guesstimate that the connection of UNO 5V to Shield 3V3 allowed back feed into the UNO by any of a number of possible paths. UNO Vin connects to shield ground and a second UNO ground connects to a second UNO ground - so if the UNO was powered via Vin you'd expect the power supply to have been shorted. This might damage some power supplies but usually not. </p>

<p>Can you please advise what voltage was connected and to what pin. And do shield pins all offset by 1 on the other side, as I've shown?</p>

<p><img src="https://i.stack.imgur.com/aqz5m.jpg" alt="enter image description here"></p>
