Hello,
I have built a basic circuit for the PIC18f4550 using a 20 MHz crystal from
As soon as the circuit comes near ( 2-3 cm) another surface (paper or the wooden table) the usb disconnects. When I investigated I found the voltage on D+ signal line went down from the required 3.1V(approx) to 1.45V as it neared the surface, thus initiating the disconnection.
Connecting just the ground side of an oscilloscope to the ground on the circuit also cured the problem. I have no idea how to modify the circuit to make it more stable. I assume it is interference in the clock signal that is causing the problem, although this is only a guess.
Any help would be greatly appreciated.
Best regards
Mike.