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5x7 Matrix Issue

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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.:D
 
I bought one of **broken link removed**. It's fully TI compatible so it works with their software. TI's JTAG uses a 2x7 header.

I also have a **broken link removed** Spy Bi-Wire unit.


They're designed to run at ultra low power levels and just blip up to high speed in short bursts when needed.

Sweet!:D I'm surprised you didn't get them over at SparkFun. Ah, it's a canuck site; going to have to have a look around that one. Thanks.:D

I'm going to have to watch your progress on this 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 :)
 

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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.
 
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