help with the analog digital conversion

[faiselz]

hi; i am using the example progam ex_admm.c

can someone tell me, what is the value of the binary number that will be obtained as a result of the ADC conversion due to , for example a 6V input at the analog pin on the PIC? Is there a formula to relate the analog input to the resultant binary number after the conversion..

I will appreciate your help dearly.. thanks..

[newguy]

If the A/D converter is set to 8 bit resolution, change "1023" to "255". The following is for 10 bit resolution.

binary reading = (analog voltage/reference voltage) * 1023

Example: PIC's A/D Vref+ (positive reference) is +5V, analog input voltage = 3.0V: binary reading = 613.8 which may appear as either 613 or 614.

Note that there is a limit to the actual Vref+ you can use if you opt for an external reference voltage. For most PICs, if Vdd = 5V, the lowest Vref+ can be is 3.0V. The highest Vref+ can be is something like Vdd + 0.3V. Consult the PIC's data sheet for guidance.

These calculations assume that Vref- is 0V (ground). You can set Vref- to a non-zero value, but then the calculation for binary reading above is not valid.