12 bit A2D on 18F46K80, need a bit of help for figuring TAD and getting correct value

[Aussie Barry]

Hi,

If you change your voltage divider to a 50%-50% configuration (say 4k7 and 4k7) and then set the reference voltage for the ADC to internal 4.096V, each step of the ADC will equate 0.5mV
Multiply your ADC reading by two and then manipulate the result to read "X.XXX Volts" per Henrik's LCDOUT routine.
Yes, I understand there may be some slight inaccuracies but I have found this approach to be quite effecting in recent projects.

Cheers
Barry
VK2XBP

[ecoli-557]

Henrik-
That looks like a cool way to do this, I have never used these operators, but I will try them all, just to see more about them.
It looks much more efficient than what I had done - multiple dividing......

Thanks! I will let you know how it turned out.
-Steve

[ecoli-557]

Barry-
I understand what you are saying, and yes, I am using the internal 4.1 reference - 1st time in fact to rely on an internal!. I was trying to use more of the available resolution on the ADC. If I do a 50% voltage divider, I have 2.5 volts against a 4.096 voltage reference. The divider I am using, uses more of the resolution of the 4.096 reference, 3.23 volts against 4.096 which gives me a little headroom above 5 volts.

I have done that in the past, but felt that I left some resolution on the table. This way does work, perhaps not straightforward, but I think it does give me more bits of resolution that can be used.

That being said, if I hadn't found a way (though it was more clunky than Henrik's) - I was sure thinking of doing just that!

Thanks and Regards to All,
Steve