On 4/25/07, Jinx <joecolquitt@clear.net.nz> wrote:
>
> BTW Philip, I did realise you've got 12F629 and suggested other
> methods as PICs are very easily sampled from Microchip (do it)


See, these are exactly the kind of suggestions I need! :)

If you're going to do this with the 12F629, which has no PWM and
> no ADC, start with the basic 50Hz timing. You may use the internal
> 4MHz (not terrifically stable) or a crystal. 4MHz will give you 1us
> instruction time, which is the potential resolution


I've already run into some odd timing issues with the simple LED flashers
I've made.  1000 miliseconds seems suspiciously more like 1500-2000.   Are
the internal crystals on these chips hugely affected by the input voltage?

50Hz = 20ms per cycle = 16-bit timer loading of 10000. An IRQ
> using this will give you the start point of each cycle


I don't understand this at all, but i'm guessing it's just not being
familiar enough with the language yet.  At least I now know what to search
for. :)

What you have to do during each cycle is determine what period
> the outpin pin will be high, and what period it will be low. How you
> do this depends on what resolution you want. If you want 30:70,
> then you'll need to put the pin high at the IRQ, count 3000 IC and
> then send the pin low until the next IRQ, 7000 IC later. That 3000
> could be counted using TMR0 or hard-coded loops and a table or
> variables


Ok, I ran into one little comment on a random page that was explaining
something similar.  I'm trying to wrap my brain around what you're saying.
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