Arduino Mega cannot be detected by any computer

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Hi all,

I have an Arduino Mega 2560 which was purchased 3 weeks ago. Recently, I encountered a problem where my Arduino COM port does not show up on the Arduino IDE or device manager. As seen in the picture below, my Arduino board can still supply power to the LED via a USB cable so it is not completely dead.

The last time it worked, the TX and RX LED lit up when connected to a PC. I do not think that the USB cable is the problem since if I connect another working Arduino board with the same USB cable, the computer detects it as COM 6. It is not possible to perform the loopback test since the neither the IDE nor computer can detect the COM port of my Arduino Mega.

Since I cannot see any burn marks on my Arduino Mega, I do not think I have fried it. I would appreciate it if you could provide advice on how to resolve my problem.

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Sorry, that is no proof. A transistor gate puncture is all it takes, and you would need to decap the IC and use an electron microscope to see it.

You could try some alternate programming methods like the ICSP.

What was the last hardware it was connected to before it died? Did you ever program the 16U2?

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Before it died, it was last connected to my computer via a USB cable. The components that it was connected to was a 4 bit counter (74HC93) and some LEDs. I have made several programs with the Arduino board. I will look into ICSP as an alternative programming method.

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Perform a close visual inspection around the 16U2 just for good measure. It performs the USB function.

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Did you have appropriate current limiting resistors on the LEDs? If not, one or more digital pins may have burned out, taking other parts with them.

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What should I be looking out for when inspecting the 16U2 chip?

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Each of the LEDs were connected to a 1k resistor from the output pins. The power supply used from the 5V pin of the Arduino board.

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I presumed my board was dead so I temporarily grounded the 5V pin to attempt to destroy the rest of the system. Somehow, it made the board recognizable by the computer. When I uploaded a program, the serial monitor was printing values like expected. The screenshot of device manager is shown below.

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I don't see how grounding the 5volt pin could do anything to the USB<>Serial chip or MCU.
All you did is overload USB supply from the PC through a resetable fuse and mosfet switch on the Mega. That might have cleared the cobwebs out of the PC.
Leo..

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It seems you're correct. The Arduino board only lasted for an extra 2 days before it became undetectable again. The ports that I know still work are the 5V pins, D9, D12, ground pins and Vin.

For the rest of the other I/O pins, I cannot verify their operation since they were last configured as inputs. Thankfully, I have another Arduino board which still works.

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