re: size, good point. My guiding principal is no bigger than a 2x16 lcd and as thin as possible. I was able to make a guino from a
rbbb kit and an lcd that was 60% the size of a scangauge, should be able to beat that with a custom board.
Re: shield, if someone locates an arduino board template for Eagle, I can slap a PCB diagram together. Also, you *could* pop the guino chip in your 'duino and program it that way, then put it back in the guino. Actually that helps build the case for keeping the programmer seperate.
re: car wiring, possibly just solder if you are up for it, or use the red trailer wiring clips if not. I found stripping the wire in place then soldering to be about the same effort and a whole lot more reliable. I heard mention of other types of taps, can someone research that a bit more?
re: programming, don't know. It was an issue before we even got here. I think the safe thing to do is to include the couple transistor rs232 circuit adapter, and have some folks try their usb adapters on that. Or use an existing 'duino to program the chip.
Anywhoo, here is my first stab at pcb design, don't laugh
I have not added a voltage regulator or programming interface yet.
Edit: added regulator. With a pre-programmed chip it just might work
