This is really starting to bug me now. I've tried AT90S8515 and now an ATMEGA16 and cannot for the life of me get this to work. I ditched the AT90S8515 as I didn't think I'd get the clock speed required for USB so went down the ATMEGA16 route that I had in my electronic spares/store. Have tried crystals from 20->12 but with no luck. I'm running the mcu at 5V and have used 68ohm resistors at D+ and D- with a 0.5W 3.6V zener diode down to ground after the resistors from the mcu. I'm using a combination of two pullup resisters in series (to best acheive 1.5kOhm) from D- to 5V.
I'm using the sample code from the vusb project and have tried the data and mouse one to run on the mcu. They all end up with it not being recognised. I'm at the point of ditching it and going a dedicated USB to serial chip.
Unknown Device
Re: Unknown Device
Never mind, disregard this post. I went through a few pages and found an ATMEGA8 project by some polish guy that was using 100ohm resistors on the data lines with a 1.5k pullup on D- and a 1M pulldown on the D+. While checking out this I found a few other things that were seriously wrong with my circuit. It's been a while since I've tinkered with my AVRs. Forgot a pullup resistor on the RESET pin so it was floating and also had the wires from the USB for D+ and D- swapped around. So I guess the next time I won't be making my breadboards off late at night 
Alls good and now comes up as a HID mouse.
Alls good and now comes up as a HID mouse.