Thanks Beebop... Im looking at the PICDEM FS USB User Guide at the schematic. Im wondering what they use that mosfet for. Looks like it blocks the VBUS (+) from the rest of the circuit if the user supplies power via adapter. Would that be correct?
Sound correct to me. With no voltage at pin 3 of the regulator, the gate is pulled down to ground by R22. When the user plugs in an adapter there is a positive potential on the gate which shuts down the fet. Quite an idea; I'll have to remember that one.
My version of that PICDEM FS USB board. Less Parts. Full PORTB output for use with w/e. Fully usb powered (or ICSP powered).Should be smaller and will make it have like a small expansion port. like 6-10pin for various addons. For testing. Mainly for me but since im posting the schematic feel free to use it for w/e. Im making this mainly to be a cheaper solution to the original microchip PICDEM FS USB.
Original $60
Mines would cost maybe $20 (max) to make Once you figure in the PCB Creation. The most expensive part would be the PCB & the PIC itself
Just a suggestion, but if your including the programming header, AND allowing full access to port B, I think you should include the protection circuit (from the datasheets) that prevent the external circuit from interfereing with the programming and vice versa.
It wouldnt matter on a normal circuit, but on a board designed to be 'played' with - I would highly recommend this.
I shift over from datasheet pdfs to tips & tricks pdfs to manual and am always changing add/removing items. Thank you for the tip... ill be sure to add that in.