On Mon, Mar 10, 2003 at 11:37:48PM +0000, Laura Adamson wrote:
> I chose the PIC16c84 because it was the chip that uni had the most
> information on, other than that there is no reason for using that particualr
> chip.
>

Understood. We have a lot of reasons why you should consider upgrading.
I've summarized them here:

http://www.finitesite.com/d3jsys/16F628.html

All of the arguments listed apply to the 16F87X, 12F675/12F629, and the
16F676 familes of parts.

> The voltages will be between 0v and 0.5v.
> There will be up to 8 inputs.
> I need the outputted byte stream to tell the PC which input source it is
> looking at and whether it is high or low, for each of the sources in turn,
> running in a loop. E.g. 0011 would mean source 1 is high and 0100 would mean
> source 2 is low.

A raw PIC won't be able to discern 0V and 0.5V. So you'll need a voltage
multiplier, or an external comparator to differentiate. Something like a
couple of LM339 quad comparators should do the trick. Attach to PORTB, turn
on the weak pullups. Generate a 0.25V reference voltage using a couple of
precision resistors, and off you go.

BAJ

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