Arduino Uno R3 not recognized by windows

[tslewis01]

I have 2 Arduino Uno R3 boards (original, not clone or otherwise). One board is recognized by windows and the other is not. the two boards are identical and even the one that is not working WAS working just fine. When I plug the board in via USB (with no wires attached), the good board causes the computer to beep and is available to program through the IDE and is available to assign a port in the IDE. For the bad board Windows either does nothing or windows says that the last USB device was not recognized and naturally the IDE does not allow assigning of a port.

The board was working perfectly and was actually in use and then just stopped running. The working program has an Ethernet shield W5500 and an IR receiver. I have removed the W5500 and the IR receiver and wires so I am just trying to get the board to be recognized by windows.

In windows device manager, I can see the working unit when I plug it in via USB but when I plug the bad unit, nothing shows up in Device Manager.

The green "on" LED on the board is lit. No other LEDs are lit and I have no wires plugged in. The USB cable is plugged directly into the PC in a USB 2.0 slot and the cord is only 1 ft long. this same cord works fine for the good board and I have plugged the USB cable into multiple ports on the PC. The green light is on so the USB cable is FULLY inserted. The same scenarios occur with my laptop.

Because the other board (exactly the same type, etc), works and is recognized by windows, I do not think it has anything to do with Windows, drivers, etc. but rather the board and because I cannot communicate with the board, I am stuck.

I have also tried to put the device into DFU mode by briefly shorting two pins (see red circle in picture) but that also does not cause windows to recognize the device.

How do I "factory reset" my Arduino Uno R3 so it is recognized by Windows?

[jremington]

@tslewis01

The board was working perfectly and was actually in use and then just stopped running

There is no "factory reset" option for the Uno R3. In the likely possibility that it was somehow damaged, it can be repaired, although the cost of repairs might be more than the cost of a new Uno R3.

What was the Uno connected to, what was it doing, and what were the immediate circumstances surrounding the event during which it stopped working?

The more complete and accurate your answer, the more likely that forum members can make a good guess about what is wrong.

[tslewis01]

Thank you for the reply jremington. As stated in the description, the device was connected to a W5500 ethernet shield and an IR receiver. It was receiving IR commands and relaying them to the internet. it was stationary and in a fan cooled cabinet. it was working one day and then it was not the next. The unit was new had been operating successfully for about a week.

[jremington]

Your post is a bit confusing. Were both boards running the same code, with identical connections, in identical environments?

Please post a clear, focused photo of the wiring. Even a slightly loose wire can cause fatal electrical noise. Swap USB cables to make sure that cable is not defective.

Although MCUs normally run 24/7 for years on end without detectable faults, it is possible that one of the components had a rare defect leading to a very premature failure.

If so, and since it is not recognized by Windows, that would most likely be the ATmega32U2 chip (the USB to serial interface), just below the red circle in your photo. In that case you can still program the ATmega328P chip using an AVR-ISP programmer, and possibly with an FTDI programmer via the serial port pins.