After having the Arduino Uno running for a short period of time, it seems to no longer communicate over the USB port when connected to the computer. It still seems to turn on and run the program uploaded. However, it no longer receives or outputs any data and any attempts to re-upload code are met with timeout errors in the Arduino IDE. The TX/RX lights do not blink at all, but the "L" light always flashes right after the Arduino is plugged in.

I have the Arduino/Genuino Uno board selected in the Arduino IDE.

This is a legitimate board that I bought directly from Arduino.

Loopback test fails.

Nothing is connected to any of the pins on the Arduino whatsoever.

I have an Arduino Nano that communicates fine with my Windows 10 PC so that rules out the drivers and the PC itself.

My computer still recognizes the USB device as an Arduino Uno and assigns it to COM5.

Leaving it plugged in for a solid 15 minutes shows no chips on the board getting hot to the touch.

I have tried resetting the board before, during, and after attempting to upload code, no dice.

Are there other steps that I can take to try to fix the board, or am I going to have to accept that I fried the ATMEL16 chip on my Uno?

  • if the port shows up as Arduino Uno, then the 16u2 is ok. you could try USB to TTL Serial adapter on RX/TX.
    – Juraj
    Jan 12, 2020 at 6:45
  • @Juraj Is that what this is? rootsaid.com/arduino-usb-to-serial-converter-programming Jan 12, 2020 at 14:36
  • yes, but never call it RS232. R232 is a different communication protocol on electrical signal level. the Arduino RX/TX pins are TTL UART
    – Juraj
    Jan 12, 2020 at 17:33
  • I think you have fried it really, it happened to me before, I accidentally forwarded 12v to 5v pin on an Arduino nano, I quickly shut off everything I unplugged the Arduino board from anything connected to it, and connected it to computer, the computer recognize it as a USB serial device but it never uploads and I also found that the temperature hits more than 70 C° so it becomes very hot to touch. So yeah I think your board is now burned, ACCEPT if the problem is in the ATMega328p chip itself. Jan 13, 2020 at 18:09

3 Answers 3


As @Juraj mentioned, if it's enumerating as a serial port, the atmega16u2 is fine.

You may be able to replace the atmega328p/au. It will take some doing; you'll need to remove the chip, insert a new one, and use another Arduino as an ArduinoISP to program the bootloader into your new blank atmega328p.

Any chance you might have uploaded a sketch that is spamming the serial port on startup? If so, try this procedure (h/t to the Arduino forums, it has saved my bacon a number of times):

  • Disconnect the usb connection
  • Begin holding the Reset button
  • Connect the Arduino
  • Initiate upload (while still holding Reset continuously)
  • As soon as you see the RX light flash, release the Reset button.
  • The first attempt to upload will fail, but with luck, the second try will occur before the 2-second bootloader delay ends (and your sketch begins to execute).

If this works, I'd suggest including a delay(3000); or similar in your setup().


try changing the baud rate according to the code...

the standard baud rate is 9600

  • how would it help for sketch upload?
    – Juraj
    Jan 12, 2020 at 17:34
  • I meant that if the baud rate on the serial monitor is different then you wont be able to see the output Jan 12, 2020 at 18:32

it happened to me. Try reinstalling the arduino board, that is, enter the board manager, remove the board and the link from your board, restart the computer and then enter the link and update the board, it is a driver problem. Greetings.

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