How to adjust values to a new range

[Demon]

I have 10-bit ADC reading with a usable range of 400 - 930.

How can I adjust that value to create a range of 100 to 230?

I've been dividing the ADC by 4 to get a PWM of 0 to 255, but all PWM values below 100 are useless, and values above 235 will shorten the life of a LCD.

I'm at my wits end after 2 days.

[richard]

pbp has a max and a min commands
by combining max and min you can constrain a variable to a
range of values

[Demon]

But that will still leave a dead space at the beginning and end of the pot. I need to convert on the fly a value from 400-900 to 100-235.

There has to be a formula to do this. I never got far in algebra in school. I don't even know what to use as a search string in google.

[Jerson]

The concept of mapping a range should be clear by this code example in C explained

// map a value(inputlow to inputhigh) to the range(outputlow to outputhigh)

int16   map(int16 val, int16 inpl, int16 inph, int16 outl, int16 outh){
int32 tmp=MAX(val,inpl)-inpl;                         // tmp = (maximum of Val and inputlow) - inputlow

    tmp *= (outh-outl);                                      // tmp = tmp * (outputhigh - outputlow)
    tmp /= (inph-inpl);                                       // tmp = tmp / (inputhigh - inputlow)
    tmp += outl;                                                // tmp = tmp + outputlow
    return MIN(tmp,outh);                                 // return the lower of tmp or outputhigh
}

[Demon]

I just realized I didn't express myself properly.

As I turn the pot, the formula should convert from 0 all the way to 1023, to a new range of 100 to 235.

Or else I have that dead spot under 400 and above 900.

[Demon]

... tmp = (maximum of Val and inputlow) - inputlow...

I'm puzzled by what is Maximum of Val? Is that the actual ADC input?


EDIT: Oh, I get it, it's the maximum value between the input (ADC in) and InputLow (400).

[Demon]

Freaking awesome!

[Demon]

Aaaaaaaannnd I'm screwed.

I go over 65,025 and I'm barely 1/2 to 1023 ADC input, that puts me over the WORD limit. I looked at the compiler options in MCSP and it says PBPL is for 18F only, I'm using a 16F1937 for this project.

I don't know what my options are at this point...



EDIT: Hmmm, what if I divide my input by 4, and adjust my input range accordingly...


EDIT SOME MORE: WOOOT! It works freaking awesome! Thanks Jerson!