> A PIC is connected to several analogue sensors. These sensors
> have FSDs of 5V or 12V scaled down to 5V. A user inputs an
> ASCII string so that the PIC will alert them when the sensor
> meets the requirements of the string

What's your user entry method like?  12-key pad?  PC keyboard?
IIRC, in a later message you say "no PC involved"...

If it's a stand alone device, and your user punches in on a keypad,
why not remove the decimal?  Last night I deposited a $30.00
check in an ATM.  I punched in "3", the machine displayed
"$0.03", then I followed with three zeroes, which offset the "3" to
the proper value.  The machine just slid numbers to the left as I
put in new digits.  It displayed the decimal point, but I didn't put
it in, and for all I know, the machine ignored it in all of its math.

Of course, this only works if you control the entry of the ASCII
data.

I was also thinking that it might help if you can "re-scale" the
inputs, such that a 4.092V reference could be used.  That'd
make it a little easier to compare voltages in assembly, by
going from ASCII->BCD->binary.  ASCII->BCD is easy, just
a matter of the proper offset value, and BCD->binary (and
back) has well-established methodologies.  I suppose you
could also try running your PIC at 5.120V, and then not
need to rescale the inputs.

I may be missing the problem all together, but I've already
had a long day.

Mike H.

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