I was communicating between my computer and my Arduino Uno R3 through Bluetooth using this Bluetooth module. The connector I use has a red wire where it connects to GND, and a black wire where it connects to +5V.

enter image description here

                ↓        ↓  to Uno ↓       ↓
               +5V      GND       pin 0  pin 1

I forgot this one time when I connected the Bluetooth module to the Uno, so the polarity was reversed. This fried the Bluetooth module.

After getting a new module, I discovered that the Uno was apparently fried too. Plugging a USB cable into the Uno made the little green integrated LED turn on, but that was all that happened; none of the pins put out any electricity. When I tried to upload a program, it gave the infamous avrdude: stk500_getsync(): not in sync: resp=0x00 error. I could upload programs to my other Uno fine, and I could not upload to the broken Uno on my other computer.

Two of the Arduino experts I know told me that the ATmega328 chip might be the only broken part. Is this likely to be the case? I have an Uno R2 with a working ATmega328. Would temporarily replacing the R3's ATmega with that R2's ATmega have a change of damaging anything?

  • Generally the black wire is ground and the red wire is +5v
    – TheDoctor
    Feb 12, 2014 at 22:24
  • @TheDoctor I know. The connector I used looked sort of like this. When I connected it to the Bluetooth module, the pins on the bluetooth and the wires on the connector were ordered in such a way that the connector's red wire represented the bluetooth's ground. Feb 12, 2014 at 22:36
  • looks like youre having the same problem as discussed here: arduino.stackexchange.com/questions/17/…
    – TheDoctor
    Feb 12, 2014 at 22:45
  • 1
    @TheDoctor Not exactly. That problem is a symptom of this problem. Feb 12, 2014 at 22:48
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    Another possibility is that the bootloader got erased by the accident. Since you have another Uno, you could try using the ArduinoISP sketch on your working Uno to try reprogramming your non-working Uno. Feb 28, 2014 at 3:16

1 Answer 1


Besides breaking a pin while removing the IC from its socket, or static electricity during manipulation, I don't see what could fry the ATmega.

However, it is possible that the R2 ATmega has a different bootloader and that may be an issue.

If I was you I would just remove the ATmega from the R3 board and test it on a breadboard (don't need a lot of components to do that); at least that could tell you if it is fried or if it is the R3 board that is fried...

  • 1
    Although bootloaders may be different, they don't rely on board revision. I know there was a switch of bootloaders in the past because the new one was smaller and therefore left more flash for the program. The board release is mainly different for couple signals being routed to extra pins on the headers.
    – jippie
    Feb 13, 2014 at 5:50

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