did not find any USB device "usb"

[kitefan]

I'm new to Arduino and I'm trying to decide if I "broke" it.

I have an Arduino Uno R3, running the IDE on a Mac with OS X 10.6.8. I've been through several sketches but tonight was working on motor sketch tutorial using a h-bridge and 9 volt power supply to the arduino.

The sketch and arduino worked perfectly with a switch to reverse motor directions. I disconnected the power and USB and made a change to the sketch to bypass the switch and change motor directions after 3 seconds.

When I connected the USB to the Arduino I couldn't upload the sketch. It doesn't show on the USB port list. I have tried using another mac and also a Windows machine with the same results.

When I plug in the USB cable, the ON led lights up and the onboard LED (L) stays on constantly. Did I fry something?

[adafruit_support_bill]

Have you tried a different USB cable?
Is the Arduino still running the last sketch you uploaded?

[kitefan]

I tried one other cable (that's all I have) and it made no difference. It does still run the last sketch I loaded.

[adafruit_support_bill]

Sounds like the Atmega328 MPU is still functioning, but the 16U4 processor for the USB/Serial interface is not. Not sure what causes this to happen, but some have been able to resurrect unresponsive UNOs by re-flashing the firmware on the 16U4. The procedure is here (Note that older UNO boards used an 8U2 - which is essentially just a less powerful version of the 16U4):http://arduino.cc/en/Hacking/DFUProgramming8U2

[kitefan]

Success:)

This website saved me: http://arduino.cc/forum/index.php/topic,92148.0.html

Apparently the "standard" dfu-programmer doesn't recognize atmega16u2. After downloading the source, patching it to include the 16u2, modifying the bootstrap file to find aclocal properly I finally got the chip erased and reprogrammed.

Thanks for the help.

[adafruit_support_bill]

Nice work! Thanks for the follow-up