USB not working on my UNO

Development Tools IDE 1.x
1

I was working with my UNO, upload a sketch, make a code change, try to upload modified sketch, then boom, the Arduino's serial not had disappeared.

I disconnected and reconnected the UNO, nothing. The power led is on.

I tried a different UNO on the same computer with the same USB cable, it's working fine.

I tried the problematic UNO on a different computer with a different USB cable, nothing. I'm using OSX and I had the console open to see the kernel messages. When I plug a working UNO I get the "AppleUSBCDCACMData: Version number - 4.1.15" messages, but when I plug the bad UNO in, I nothing show up in the logs.

I reflashed the atmega8u2 with my AVRISP mkII. That went fine. I can also run a verify, that's successful. But still nothing show up in the list of USB device attached.

This particular UNO is a bit different the my other one (and the pictures I see online). The atmega8u2 has a resonator instead of a crystal. It also doesn't have the holes to put a crystal where the resonator for the 328 is. That makes me wonder if the fuses on the atmega8u2 shouldn't be different then what the instructions say to use:

(-U lfuse:w:0xFF:m -U hfuse:w:0xD9:m -U efuse:w:0xF4:m -U lock:w:0x0F:m).

The sketch that was uploaded to the 328 before the it broke runs fine.

I probed the resonator of the atmeg8u2 and I see a 16mhz sine(ish), the same as what's on the 328.

Any recommendation on what else I should look for?

Thanks in advance!

-yvest

2

Try a different USB cable.

3

As mentioned, I tried using a different USB cable with no luck.

Any other suggestions?

Thanks you!

-yvest

4

Use an ISP for uploading if you can live without the serial connection to that board.

If not, take a big hammer and beat the devil out of it. Remove any working parts before that takes place.

5

Other than the USB cable, do you have anything connected to the bad board?

6

Coding Badly: Nope nothing else plugged into the UNO.

madworm: I was considering your second suggestion but I figured I'd first try to see if I could reflow the solder of the atmega8u2 using hot air. The soldering in this area of the board didn't look very good. I figured that if the reflow didn't help, I would simply take the atmega8u2 off to make sure it didn't create any contention on the serial lines.

Well after the reflow, the USB port started working again! So far, it seems to be holding up.

Thanks for time!

-yvest