Schematic for simple demo

[iandonahue]

Newbie here... I'm just starting out with some of the demos; Using Pic Basic Pro with Code Studio and trying to successfully run the "mouse scrolling" demo that makes your cursor go in circles. Everything went pretty well with the compiling and programming, but I'm getting the usual "device not working" tag from Windows. I think the problem is the wiring on my breadboard and I'd like some help. Does anyone have a schematic for this simple trick? I'm using a 18f4455.

Any help would be appreciated.

[skimask]

Newbie here... I'm just starting out with some of the demos; Using Pic Basic Pro with Code Studio and trying to successfully run the "mouse scrolling" demo that makes your cursor go in circles. Everything went pretty well with the compiling and programming, but I'm getting the usual "device not working" tag from Windows. I think the problem is the wiring on my breadboard and I'd like some help. Does anyone have a schematic for this simple trick? I'm using a 18f4455.
Any help would be appreciated.

Let's see your schematic and program... Maybe we'll find a simple flaw in what you have already.

[Bruce]

Here's a generic USB circuit.

[dlchambers]

I found this to be useful:
http://www.create.ucsb.edu/~dano/CUI/

Scroll down to "Section 2" for details on a bare-bones circuit.

[Kamikaze47]

Does any1 know what the purpose of the 1Mohm resistor across the crystal?

[skimask]

Does any1 know what the purpose of the 1Mohm resistor across the crystal?

http://www.tla.co.nz/xtal1.html

[Kamikaze47]

http://www.tla.co.nz/xtal1.html

From above link: "...Many microcontrollers have this resistor internally and may have different values for different frequency operations. If so, then the external resistor is not needed."

Pretty much every PIC data sheet i've looked at indicates that this resistor is internal to the PIC. (e.g. PIC18F4550 data sheet pg. 24).

So I guess all of the circuit diagrams that indicate to add this resistor externally for a PIC would be incorrect (or in the very least, redundant).

[skimask]

From above link: "...Many microcontrollers have this resistor internally and may have different values for different frequency operations. If so, then the external resistor is not needed."
Pretty much every PIC data sheet i've looked at indicates that this resistor is internal to the PIC. (e.g. PIC18F4550 data sheet pg. 24).
So I guess all of the circuit diagrams that indicate to add this resistor externally for a PIC would be incorrect (or in the very least, redundant).

As far as I know, that's entirely correct.
You switch config settings (i.e. XT, HS, etc) to basically change resistors inside the PIC for the different drives levels required for external crystals.
Higher speed crystals/frequencies need more juice to switch logic levels, higher slew rates, which require more power.