> One question (in general): any particular reason folks are so enamored
with
> the 8 pin parts? Personally I avoid them like the plague due to extremely
> limited I/O and complete inability to have a bootloader. Unless you're
talking
> about a 1000+ unit run, the costs between the 8 pin part and a hefty
capable
> 40 pin part with all the bells and whistles (12F629 and 16F871 as
examples)
> is only a 3X price difference. In hobbyist/small scale run terms, the
price
> is negligable.
>
> So I'm just wondering if there is an advantage to develop with a extremely
> limited target as opposed to a larger more capable part?

I come from a software backround, so I'm used to thinking of the problems
modularly.  I find it a lot easier to write some modules into a few 12F629
or 12F675 and have a central larger chip that runs the project but has
simpler code than it otherwise would have.  It's sort of like doing
multi-threaded programming by having a seprate PIC for each thread.

For example someone recently asked about decoding an IR remote that could
have a few possible signals.  My approach would be to use a 12F629 to handle
the input from the IR detector and deciding which button is pushed.  It then
has 5 outputs left to pass 5 possible values to a larger pic or since only
one button will be pushed at a time, I can represent 32 possible buttons on
the 5 lines.  That makes the function of receiving an IR signal a lot
simpler to do in main PIC because the hard part is done in a separate device
so I don't have to worry about real-time issues and polling the IR detector
in my main chip.

I'm also working on driving an RGB led just to play with it like the author
of the original post.  The 12F675 gives me 3 output lines to do PWM on the
LED sections, and I'm still left with 3 inputs.  That's plenty to read a
serial instruction to select a colour or use an analog input to base the
color on/etc.  There is no reason to use a larger chip.  My entire PCB for
the project is smaller than the footprint of a 40-pin DIP.

I asked earlier about the small chip + shift registers vs a large chip with
lots of IO.  Ultimately I decided to use the large chip.  In designing the
PCB, I had a lot of trouble routing all the lines coming from the PIC on a
single sided board.  With shift registers, I just need to send 3 wires to
each SR, 2 of which are common to every one, and the board layout is much
easier.

Jason

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