[Peripherals] PIC Updates

[Mel Chua]

(Moving conversation to peripherals@ list so others can chime in - for 
reference, Ian and I are talking about TeleHealth hardware, as I'm now 
his firmware codemonkey.)

> The 4553 just provides 12b vs 10b, which, for a medical application of 
> any sort, seems absolutely crucial.

You're writing this down in some sort of "chip selection" section on the 
page so that future hackers thinking of porting it to a different mcu 
can see what you're thinking, yes? ;)

> If you look at the schematics, the proto board provided by Microchip is 
> extremely similar to the CUI.

Excellent. Well, for my purposes, I don't really care about the layout, 
just that the chip has appropriate things hooked to it to make I/O work 
(or that I can very easily make it be thus).

> Also, for dev kit, the 4553 and 4550 are identical, iirc. I have 3x4550 
> and 3x 4553 in the mail, I figured I could proto a CUI for you for the 
> beginning stages of hacking, if you needed.

Sure - I can send you an address if you need somewhere to ship. Dev kits 
come nicely prepopulated with buttons and etc. soldered nicely onto the 
board, so... whichever you think is faster. I won't order a dev board 
unless you say so.

> By Linux Bootloader via USB -- I meant that it would be very nice if 
> there was a Linux program which could update the PIC image over USB.

Oh! Yes! Yes, there is. I plan on doing all my programming in Linux via 
USB. I'll worry about making this part work for other people. ;)

While it's possible to program the PICs over USB in Linux, it may not be 
immediately possible to do so on the XO (as in, "how much pain is it 
going to be to port the compiler etc?" "I don't know.") I figured that 
would be the first thing to tackle after we get a basic system up and 
running; it would be glorious to expose an entire generation of kids to 
hardware hacking early on.

Arjun mentioned that it would be sweet to have a "look, kids - code your 
own USB peripherals!" kit, which I've made before, along with a "here's 
a template python script on the other side to hook your peripheral I/O 
to whatever other programs you want!" thing. Which sounds like what we 
want. Closed source, though, as that was for a company. So I'll have to 
recreate it later - it will probably be a generic-ization of the 
TeleHealth module.

> Also, instead of 'minimize unused pins' I should have said that the I/O 
> that I specified are the minimum, and analog/digital IOs that could be 
> provided past that would be great.

Cool. I'm using the wiki as my spec sheet, fyi, so if that page changes, 
my code will accordingly.

-Mel