This is the first time I'm using my Arduino. It's an Arduino UNO R3. I have two boards. One works, but the other doesn't. I changed the ATmega328P from the broken one to the good one and it works, so I can confirm that the controller works. The issue seems to be in the board.

When I plug the board it doesn't come up either in Mac or in Windows. The LED blinks and the output pins have voltage, but it seems that it's only getting electricity from the computer, it's like the data channels don't respond. The other board works perfectly both on Windows and Mac.

I checked the logs on the Mac and nothing changes when I plug the board. It's like I'm not plugging anything.

Is there a way to reset the board only? Maybe a component was badly soldered in the factory. I can't use the warranty because I got the board last year and never used it until now.

  • 1
    Might have something to do with the USB driver IC (I believe they're FTDIs?) if your computer is not recognizing the board. Unless you have a hot air rework station to replace the chip, you are probably just better off buying a new board.
    – Nick Williams
    May 31, 2014 at 0:21
  • Just to confirm - you are using the same cable with either board, right?
    – JRobert
    Jun 1, 2014 at 13:40
  • Try to reset the communication IC on your arduino uno. You can see the steps on this link arduino.cc/en/Hacking/DFUProgramming8U2
    – Handoko
    Jun 1, 2014 at 21:57
  • The board doesn't even shows up in the device manager. I unplugged. @Nick I don't have the equipment to replace the chip. At least I have the ATMega chip that maybe I can use as a replacement in case the working board dies someday.
    – zago
    Jun 17, 2014 at 23:55

2 Answers 2


The R3 uses an ATmega16u2 in place of the FTDI. It is possible that it is not loaded, busted crystal, or it has no local power to it. It is a small SMT.

You could use your good Arduino setup as ICSP programmer to talk to the ICSP of the 16u2 to see it is alive. And if so then program it.

  • I can use the working board to program the chip of the broken one but I would like to know if there is a way I can test where the issue is and maybe fix the board. Without the board I can't easily use the ATMEGA for other purposes.
    – zago
    Jun 1, 2014 at 2:11
  • First setup your good working Arduino as a ISP programmer, to flash the boot loader to the suspect Arduino Board. once working, this proves your programmer. Then use avrdude to read the fuses of the suspect. If you get a response, other then 0x00 chip id. Then it likely can be programmed.
    – mpflaga
    Jun 2, 2014 at 14:22
  • You should also check the voltages, to ensure it has proper powers. And if you got a Scope the XTAL pins to see if there is clock.
    – mpflaga
    Jun 2, 2014 at 14:24
  • do you know where I can find instructions to do what you suggest? The board doesn't even shows up in the device manager. It only gets power, nothing else. The method you propose is an arduino to arduino or PC to arduino? because the PC to arduino is not an option.
    – zago
    Jun 17, 2014 at 23:57

I have a sketch, that runs on a Uno, that detects chip signatures on other boards. You can use that to verify if the other board is good.


You just need six jumper cables, like this:

enter image description here

From your description it sounds more like the Atmega16U2 is not working, that is the USB interface chip, the small chip near the USB socket. You can use the same sketch and a similar interface to check that as well.

enter image description here

That should at least show that the chip(s) are alive and giving valid signatures.

You could use About this Mac -> System Information to see if the problem Uno is listed as some sort of USB device.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.