I have an Arduino Uno R3 and when I plug it into any computer, the computer doesn't recognize the Arduino. I checked up and the LEDs are working fine and when I open the device manager it doesn't show any Unkown Device.

What it could be? Could the ATMega be dead? I tried on two Windows 7 and one Linux machines, none recognized the Arduino.

  • Is it an official Arduino board or a clone? – Peter Bloomfield Apr 5 '15 at 23:51
  • I burned out the USB-serial converter once with a shorted USB cable and it did the exact same thing. I was still able to program it using another Arduino and everything worked fine except for the USB connection (although it was a real PITA to load sketches to). Might be something to test if you have another ISP. – Comintern Apr 6 '15 at 0:34
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    @PeterR.Bloomfield It's an official Arduino board. – RebeloX Apr 6 '15 at 8:39
  • @Comintern That could be possible, but would that affect the LEDs? Because when I plug the USB the Arduino receives power, but has I said nothing happens. – RebeloX Apr 6 '15 at 8:39

The reason that it is not connecting can be anything from wrong driver installation to the dead Atmega 16u2 chip. But I must exclude the former option as you said you'd tried on different OS and different computers. So double check the driver installation. And if does not work try to find out whether Atmega16u2 is fried or not. One solution might be to reflash the original firmware through an external ICSP programmer. If don't have any programmer but another arduino uno you might try out the gamon's tutorial on flashing firmware on the little USB to serial interface chip. Anyway if your arduino is new and official you can get the right support online on arduino.cc. but if it is a clone you may try to contact the reseller whom you bought from.

  • The problem is that when I plug the arduino it doesn't apear that something new is connected, and when I check the Device Manager there's nothing even the Unkown Device, I'll try to download the drivers again and plug it again to see what happens. – RebeloX Apr 6 '15 at 8:32
  • As I said above, you now have only one solution. If it is a new board get help from arduino.cc if it is an older one try to bring back to life the mini USB to serial chip on the board. – Harry Apr 6 '15 at 10:14
  • The board has almost 2 years so I guess the solution is to bring back to life the mini USB to serial chip, any ideas on how to do that? – RebeloX Apr 6 '15 at 18:37

I had the same problem. When I connected the board to PC the ON Green LED turned on and the arduino run the last code was uploaded but the board wasn't recognized. Changing the cable fixed this problem for me.


If your arduino runs the last uploaded sketch, the problem is with the ATMega16U2 chip in your Arduino. Try to update the firmware with this tutorial https://www.arduino.cc/en/Hacking/DFUProgramming8U2

If you can't update the 16U2 firmware don't throw away, you can program the Arduino with a ISP programmer like this https://www.pololu.com/product/1300

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