My I2c stopped working and now pin A5 doesn't work. Help!

Projects Networking, Protocols, and Devices
1

I'm connecting a raspberry pi to a 5v pro mini via I2c.
My setup is:
Pi 5V -> Arduino 5V
GND -> GND
SDA-> A4
SCL -> A5
Things were communicating fine and then just stopped.

When I tried restarting, the Pi would no longer start up if connected to the Pro Mini. I ran some tests on A4 and A5 and found that A4 set to high will output nearly 5V, but A5 only outputs .8 volts.

Can anyone explain why this has happened and how to fix it?

Thanks.

2

it sounds like you have burnt out the driver for that pin, usually done by exceeding limits, to the best of my knowledge and if I am not wrong about how robust their protection against 'stuff' is;

Short pin to GND, set as digital output and drive high - burns quick
Short pin to VCC , set as digital output and drive low - burns quick
Source more than the pin's maximum (source) current - burns out at timing proportionate to load
Sink more than the pin's maximum (sink) current - burns out as above
Attach to any voltage outside of the manufacturer specified range - burns out qiuck enough...
Attach to any fixed voltage (as in no resistor > 'R' Ohms in series between pin and) source, set as output and drive high/low - burns quick enough pending difference between drive voltage and regulated voltage (pretty sure :p)

('R' needs to make Ohm's law equation I=V/R work out where I must not exceed the manufacturer's stated maximum sink current for the pin, probably good practice to aim for I="manufacturer's stated max"/2 if using resistance low enough to worry this detail.)

I think ESD could take out a single pin under certain circumstances but I also think the deafening roar of replies if I stated that as a fact would be fairly emphatic that electro-static discharge to any pin would more likely destroy all functionality about the device.

It is more likely than anything else that it is one of the first two and at a guess one of the resistors you were using as a pullup either became shorted out itself or connected in an unfortunate way with a leg of something else poking out of breadboard nearby - are you using breadboard? You didn't happen to photograph it before touching it after the failure occurred I'm betting.

I could be wrong, I work in electronics for a day job but I am proved wrong more than often enough :wink:

The only way to fix it as a sure thing, to the best of my knowledge at least, is to replace the processor.