ADC resolution/conversion

I'm going to be using a 10-bit ADC on a PIC to measure voltages between 3.5 and below. I'm trying to calculate what value the PIC would return for various inputs assuming my reference voltages are +5V and 0V. If I understand correctly, in this situation 1 bit = 4.89mV. I got this from:



And if I wanted to know what value would be returned when measuring 3.5V it would be:



In this case 716.1, so the ADC would return 716. Using the same equation for 3V (using the above equation) I get 613.8, so the ADC would return 614. Are my calculations correct? If not, what am I missing? Thanks in advance.

 

AVR datasheets are clear that the multiplier would be 1024 instead of 1023 but the few PIC datasheets I've seen were unclear on that point. I would think it would be 1024, but unless 5mV matters then it's a minor point.

The form of the equation is right, though.

 

The 5mV won't make a difference, I just wanted to make sure I got the form of the equation correct. Thanks for the response...I appreciate it.

 

Are you sure? I would think that the 1024 above when finding resolution is correct, and the 1023 when finding the value in the ADC are both correct. 1024 in the first because there are 1024 distinct steps, and 1023 in the second because that's the max value available.

I know this topic has recently been hotly debated elsewhere on these forums, and I'm not trying to stir up trouble...I'm just curious.

 

From the PICmicro Mid-range MCU Family Reference Manual:
ww1.microchip.com/downloads/en/devicedoc/33023a.pdf
Other ADCs can have different transfer functions.