Binary to Decimal from ADC

[Bruce]

PBP doesn't support floating point, but you don't really need it for A/D
conversions.

For 8-bit A/D you can do something like this;

Quanta CON 5000 ' set this to +Vref. @5V use 5000. @4.990V 4990, etc.

Read the A/D value

ADCIN 0,ADval ' read RA0 A/D into word var ADval

ADval = ADval */ Quanta ' use middle 16-bits of multiplication.

LCDOUT DEC ADval DIG 3,".",DEC3 ADval ' 5.000, 3.962, etc,,

For 10-bit;

Quanta CON 1251 ' If +Vref = 5V.

To find Quanta take +Vref / 1023.

If +Vref = 5V then 5 / 1023 = 4.887mV.
4.887mV * 256 = 1.251 or 1251 for Quanta.

You can tweak the Quanta value to improve results. It may vary slightly from
PIC to PIC, but you want a good solid +Vref.

[RYTECH]

thx for the quick reply Bruce

i'll give your suggestion a try.

[RYTECH]

That worked great

can you suggest a voltage divider schematic for using a range of 12 - 15v knocking it down to the 0-5v needed by the pic? I dont think im doing it right...when i multiply the voltage dividers output by 3 it doesnt equal my source input level ( currently from adjustable power, but eventually will be 12v battery)

Thanks for any additional suggestions.. :

would the solution mentioned here: http://www.picbasic.co.uk/forum/show...oltage+divider be suitable?

[Melanie]

Consider the appended drawing.

Assuming a 3:1 ratio (ratio determined by R1+R2:R2), Resistor R1 has to drop 2 volts for every one volt appearing across R2. So, if we have 15v input, R1 has to drop 10v across it for R2 to drop 5v. Apply the same ratio for your Resistor Values... if we have 10K for R2, we will need 20K for R1.

The voltage the PIC will see will be Vin/(R1+R2)*R2... so if we have... R1=22K, R2=10K and Vin=12, we get...

12/(22000+10000)*10000 and the PIC sees 3.75v

10K is a good value for R2. Choose R1 so that the PIC never gets more than Vdd (most probably 5v) at the maximum possible applied input voltage to the divider.

[vastator]

Where can I find information on dec dig and dec3 modifiers? I searched through the PBP manual but came up empty.

[Bruce]

DIG is explained in the Math Operators section. DEC is a data modifier, and
is shown in sections of the manual for PBP commands that allow data modifiers like LCDOUT, SEROUT2, HSEROUT, etc,,.