It works but I don't know how!

[ccesaretto]

I have been using the 18F2550 connected to the USB port, configured has a low speed device. These are the fuses:

[ccesaretto]

Ok. maybe it's just late and I should sleep.
The configuration bits are OK, and actually the PLL postscaler divides the PLL clock by 4.

CPUDIV3 just sets the configuration bits CONFIG1L[4:3] to 10, which means "divide by 3" if using the postscaler as the oscillator postscaler, but it means "divide by 4" if the postscaler is used as PLL postscaler.

Hope this make sense for you guys.

The reason I am setting the device to work at low speeds rather than full speeds is because I need to transfer few bytes every second and I was having troubles connecting the pic to some USB hubs.

I found out that the type of cable used matters and low speed devices work with any cable, even the longest.

[PCM programmer]

[Ttelmah]

On the USB clock, for low speed, there is a /4 division, between the internal USB clock, and the USB device itself. Low speed, requires an internal USB clock at 24MHz, and full speed, 96MHz (divided by two to give 48MHz). The PLL, cannot be used with low speed operation. Section 2.3 of the data sheet. Low speed operation, is _only_ supported with a 24MHz crystal, and USBDIV set to zero. When the PLL is used, you can only select full speed operation, and the output of the PLL, _must_ be 4MHz.
Limitation of the hardware.

Best Wishes

[bkamen]

[Ttelmah]

It would potentially give some performance improvements, but CCS does not support it, so you would have to switch to another compiler....

Best Wishes