12F683 Maths and code genius reqd.

[retepsnikrep]

How can I simulate/enter this formula in a spreadsheet?
I want to experiment with the values for the the calculation.
The special 2's complement maths is making my head explode.
Thanks

ADCIN 1, Temp 'Temp = a number between 0-255
RegenPot = (Temp ** 20480) - 40

[HenrikOlsson]

Hi,
Try something like:

=TRUNC((A4*20480/65536)-40)

Where A4 is the cell in which you put your TEMP value. Now, MS insists on changing the names of the functions depending on what language you're running but I think TRUNC is what you want, as long as you're running an English version of Excel - which I'm not.....here it's called AVKORTA....

This will give you a result of -39 when TEMP is 0 and 39 when TEMP is 255 and it truncates the result (instead of rounding it) just like it will when run on the PIC.

We could get it display as a real two's complement number but I'll have to dwell on that for a moment - if needed. In the meantime:
253 = -3
254 = -2
255 = -1
0 = 0
1 = 1
2 = 2
3 = 3

And so on.....

/Henrik.

[retepsnikrep]

How can i modify the formula to get +/- 20 or +/- 10

AssistPot = (AssistPot ** 20480) - 40
RegenPot = (RegenPot ** 20480) - 40

[HenrikOlsson]

Hi,
+/- 20: Change 20480 to 10240 (1/2 of 20480) and subtract 20 instead of 40.
+/- 10: Change 20480 to 5120 (1/4 of 20480) and subtract 10 instead of 40.

Just think of the ** operator as multiplying by units of 1/65536.

/Henrik.