> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of cllow2020
> Sent: 04 December 2009 15:32
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC] increase pic program flash memory size ? possible ?
> 
> thanks jinx,

<snip>

> an0_value=(an0_value/10)*2441 / 1000   //: get back reading in mv
range
> an1_value=(an1_value/10)*2441 / 1000
> an2_value=(an2_value/10)*2441 / 1000
> an3_value=(an3_value/10)*2441 / 1000
> 
> an4_value=(an4_value/10)*2441 / 1000 *16    //: get back reading in mv
> range
> and 16x
> an5_value=(an5_value/10)*2441 / 1000 *16
> an6_value=(an6_value/10)*2441 / 1000 *16
> an7_value=(an7_value/10)*2441 / 1000 *16
> --

You would probably save a useful amount of program memory if you can put
the ADC values into an array and iterate through them in a loop rather
than calculating each one explicitly.

Also assuming you are using integers in the calculations you could save
a little more memory and improve speed by scaling the constants to avoid
the two divide/multiply operations e.g.

    an0_value=(an0_value/10)*2441 / 1000

can be reduced to

    an0_value=(an0_value * 125) / 512

and 
    an4_value=(an4_value/10)*2441 / 1000 *16

can be reduced to
    an4_value=(an4_value * 125) / 8192

If your compiler is smart enough the divisions will be reduced to shift
operations, or you could do them explicitly.  

These are not exactly equivalent; the scaling factor is 0.2441 in the
original and 0.244140 in the optimised version, giving an error of
0.016% which is probably insignificant compared to component tolerances
(scaling resistors and voltage reference for ADC. This gives a maximum
error in the reported value of 1mv.

Regards

Mike

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