Accidentlly applied 12v to digital i/o pin 7

... whoops :-[

Yes I'm an idiot I know it. The result is that now the Arduino fails to respond, power light is on but can't be reached via USB (rx light flashes but no tx)

Now the question is what have I fried, any ideas?

Thanks in advance!

You may have only fried the chip - try unplugging it from everything, removing the Arduino, then plugging it into just USB - does it still show up on your computer as a USB serial port?

You might also then attempt to do some comms with the port (hyperterminal or something like that) to see if you can get the rx/tx pins to flash. If so, then that part is likely ok.

Also, carefully check the traces between the header for pin 7 and the Arduino chip IC socket - make sure nothing has fried there. Check the socket to, see if anything fried or melted.

Then, try getting a pre-bootloaded ATMega328 (now's the time for an upgrade if you haven't!), drop it in and run some more tests on all the pins (blick sketch first, of course).

Good luck!


Ok pulled the ATMega and plugged it into the laptop. I can see the Comm port and can send data although no ones home :slight_smile: (It ain’t replying, although I’ve never communicated directly through serial so I’m not sure of the comm port settings.)

I think I’ll order a preloaded ATMega328 and see if that fixes it.

it wont reply unless you loop the connection back

tx <>rx

you can do this by jumping pins 1 and 2 of the ic socket, then whatever you send to it will echo back on to your terminal program

Which ones are pins 1 & 2 ::)

Couldn't you just run a jumper between RX and TX (0 and 1 on the Arduino board) with the chip removed?

Just ordered the ATMega128 online, and hopefully pick it up tomorrow, then we'll know for sure :)

I certainly hope you mean Atmega168 and not Atmega128, as they are not the same thing. The '128 will not work with the Arduino software without a fair amount of hacking, and is not set up the same way as the 168.

Yeah, sorry was a typo :)

If you haven't bought one preloaded with a bootloasder, you'll need a means to get the bootloader on to it as well.

Is preloaded :) Picking up at 18:00 and then I can play further !

PS TX> <RX loop is pin 1 & 5 on the chip (According to the schematic)

[Dr Frankenstein voice]It’s alive![/Dr Frankenstein voice]

Yep the chip fixed it, or at least as far as I can see. Still need to plug it into the module to check all functions but I can upload the code now :slight_smile:

Cool! Good luck!

Glad to hear you got it working; now go to the craft store, pick up a package of small googly eyes, and glue a couple on the fried ATMega and sell it on Ebay or somethin'...


1 ic + 1 ceramic capacitor glued upside down on one end = caterpillar