I have run into one of the strangest things I have seen.
I have a project that is controlled by usb. It works great until you switch off the fluorescent shop lights. Once the shop lights are turned off it stops working I will restart the software and it works again.
I can actually watch the device disappear from the device manager in windows when this occurs.
This only happens when the lights are operated. I have tried putting caps on the voltage supplies and watched for ac noise on the circuit. 30mV of ac voltage. It never fluctuates when this happens.
The only thing I can think of is not having any resistors on the d+ and d- from the usb to atmel?
Any ideas? Noise?