Mega2560 external voltage on 5V pin, no comms anymore

Hi!

I have several Arduinos. Recently on a project, I accidentally connected my regulated 12VDC supply into the 5V pin instead of Vin. It stayed like that for a minute or so, until I realised what I have done. I changed my connections and got the supply to Vin, and the last project I loaded worked fine for over two weeks.

Right now, I have no communications to my Mega. Mac does not even recognise it. When I connect the unit thru USB, I see "ON", and pin13 LEDs are lit, and RX and TX LEDs are both dimly lit. I checked with other Arduinos and others connect normally.

Does anyone have any experience on this? Is there a way I can save my Mega 2560 R3?

If there's any other information you need just let me know. Thanks.

Ercin

It sounds like you should have blown the whole board. It seems you are lucky and only blew the USB to serial converter.

That being the case you can at least use a USB to serial converter to communicate with it.

Electronics is frequently compared to plumbing. Electrons are like water, voltage is like pressure. When you try inflate a car tire to 200psi, what do you get? boom! When you overpressure plumbing, boom! pipes burst, valves break, actuators split, fittings spring leaks, stuff gets damaged.

Maybe after you realize your mistake and turn down the pressure, something might still work, but you're left with other things that are physically damaged and must be replaced. Other parts may still work but at reduced capacity or with bugs in their behavior.

I don't know what protective circuitry the amtel has on it, but it's remotey possible the mega itself wasn't killed. It'd be nice if you had some other way to tell that, like if your last-uploaded sketch blinks the led on pin 13 and it's still doing that. (or has STOPPED doing that)

You could try programming it remotely instead of via the (now dead) onboard usb.

But yeah... you probably fried the proc.

Also, when you hook up the USB cable, do you get 5v on the 5v pin? do you get 3v3v or 5v on the 3.3v pin? Or does the computer complain about overcurrent on the port and refuse to power it? Regulators are often damaged by overvoltage on their low side.

Thanks,

I've read some other stuff and found out that only the Atmega16u2 might be damaged. Some suggest reloading the boot loader. I'll give it a try and will post here the result.

I have both 3v3 and 5v normal.