PIC18F4550 + USB stops working...??

Jody · Joined: 08 Sep 2006 Posts: 182

Hello,

I use a 18F4550 with the CDC driver and this seems to be working oke..
Windows XP generate a virtual com port... I can communicate with the PIC for about 10 minutes and then I loose the all communication with the PIC...

Have a capacitor connected to the VUSB pin 470nF.....

And I am totaly confused right now..

anybody a idea???

Regards,
Jody

Ttelmah · Joined: 11 Mar 2010 Posts: 19537

Almost infinite number of possibilities. Main ones:

1) Supply problem on the PIC supply. _Must_ be 4.5v or more, and stable, if using the internal regulator (the internal regulator is only supported for '5v' applications).
2) Code that is resulting in interrupts being disabled for more than 1/10000th second.
3) Oscillator not meeting USB stability specs.
4) Poor PCB layout of the USB connection and grounds.
5) Code that is resulting in RAM contents getting corrupted.

etc. etc..

Best Wishes