On Sun, Apr 18, 2004 at 02:34:08PM +0100, Matt Marsh wrote:
> On Saturday 17 April 2004 21:49, Byron A Jeff wrote:
> > So now onto how to get it done. If you have a CCP
> > (Capture/Compare/PWM) module it's your bestest friend for such a
> > project. It'll measure the pulse widths for you, give you an
> > interrupt when it's done capturing, and has programmable polarity
> > and counting speed. It's literally set and forget.
>
> So, having had a couple of responses saying that CCP would be useful
> for this, I thought I'd better do a bit of research into CCP (given
> that I hadn't heard of it before). It certainly looks interesting,
> although from Microchip's website I can only see it available on
> some of the 18F* chips? Is that correct?

Nope. Not even close. From a cursory look, the smallest cheapest chips with it
is the 16F818 with a Digikey single chip price of $3.25 and the 16F628A
weighing in at $3.05. That's about double the price of the 12F629. OTOH
you do get more pins, more memory, and more peripherals to play with
(like a hardware UART if you happen to need it).

> If so, I might have to do
> without CCP and do it the more manual approach as I was hoping to
> do this on one of the small 8-pin 12F629 (or similar) chips.

It's a tradoff. A more expensive 18 pin part that has the hardware vs. a
less expensive 8 pin part that doesn't. Since I have stacks of both on hand
(along with 16F87X and 18F parts) I'd just pick the one that the application
requires. However as I said in my original post, there are no right or wrong
choices here, just choices. So pick based on what you have on hand, or the
price point, or if the design requires multiple tasks to be done at the same
time (A big seller for me. It's why I choose hardware laden parts like the
16F88 and the 16F877A).

The only wrong choice is something that doesn't work.

BAJ

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