Issue with Atmega16U2 chip

I am quite new to this world of Arduinos. The board I have is a UNO R3 and has been working fine as expected. But one fine day it failed an upload of a sketch or should I say it was hung during an upload and I yanked the USB cable. Ever since then I have not been able to upload any new sketches and the one that was already there is also not working since it failed in the middle of an upload. Below are the steps I have done for troubleshooting and now have hit a dead end.

Now before anything, as I explain the steps, please keep in mind that the UNO shows up perfectly fine in Device Manager on COM5 and also I am able to fetch the Board Info using the Arduino IDE.

  1. First I enabled verbose logging for uploads and got the below error message consistently.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x27
  1. I tried different USB cables, different PCs, all the same.

  2. Tried re-installing the device drivers via Device Manager. No go, same error during upload. Even tried Arduino Create plugin via browser.

Point to note: During upload, there is absolutely no activity on the TX or RX lights. The L light just stays on solid along with the power ON light.

  1. Tried doing Loopback test. Failed! No activity on TX/RX light when sending commands using serial monitor.

  2. At this point, I went ahead and got myself a new UNO R3 board. It works perfectly as expected, so 100% ruled out any issues with PC or drivers.

  3. I used the new board to find out more about the issue on the broken board. I used the following resource: GitHub - nickgammon/arduino_sketches: Publicly-released sketches for the Arduino microprocessor

When running the Atmega_Board_Detector sketch, the check for the Atmega16U2 chip via ICSP pins comes back with error:

Attempting to enter programming mode ......................................................
Failed to enter programming mode. Double-check wiring!

However, the test for ATmega328P chip via ICSP pins using the same sketch was successful.

This concludes that the ATmega328P chip on the board is fine but there is a problem with the Atmega16U2 chip/USB interface.

  1. I then decided will try out the option to reset/reprogram the Atmega16U2 chip using FLIP(DFU Programmer). So I went ahead and shorted the GND and RESET pins on the ICSP header pins. Nothing happened. What is worse is that the device still shows up as UNO R3 on COM5 in device manager. Not even resetting. (I did also try the option to reprogram it via the Atmega_Board_Programmer sketch from the above mentioned github application using my working board and via ICSP pin but obviously ran into the same error message as the Atmega_Board_Detector sketch)

This is where I need help. I am completely lost as to how to proceed. Is the USB chip permanently damaged stuck in some kind of hung state that it is neither resetting nor being open for reprogramming? Help!!


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Iam quite glad I found your post, since I seem to be having about the same problem. Board 'mysteriously' stopped working and the usual tutorials lead nowhere. Since there is some discrepancy between what you are describing and what I am experiencing, I'll first try to address some issues with your board:

  • Loopbacks behave strangely on my board, too. What I would suggest is you remove the ATmega328P from the board ant retry the loopback test (just connect TX to RX). That's the only way I have successfully been able to get it to work every time.
  • There are 2 ICSP headers (ICSP and ICSP1) on an Uno. Since the check worked for 328P on ICSP, you might wanna try the one for the 16U2 on ICSP1, since that one is actually connected to the chip.

Let me know how those worked out for you.