configuring AD converter in a 12F615

[Darrel Taylor]

I would like to implement this no-pin battery monitor into a project using a 12F683. The two devices appear to be pin compatible so I am hopint this will work. Am I sadly mistake?

The 12F683 does not have an internal 0.6V fixed reference.
So you won't be able to do it with that chip.

[Aussie Barry]

Thanks for the input Darrel and Dave.

It is amazing what you can find in the manual when you know where to look

Darrel, can you please explain how you arrived at the value 117 for the Vref_AD constant? I would have expected it to be 0.6/5*1023 = 122

For my project I was able to use another ADC pin to monitor the supply voltage so all is good (for the time being).

Cheers
Barry

[Darrel Taylor]

Darrel, can you please explain how you arrived at the value 117 for the Vref_AD constant? I would have expected it to be 0.6/5*1023 = 122

The internal fixed references are not very accurate, so you have to read the actual value to determine the number to use.

For my project I was able to use another ADC pin to monitor the supply voltage so all is good (for the time being).

Thats a bit like lifting yourself up by your own bootstraps.

[Aussie Barry]

Thanks Darrel.
I am using the other ADC pin to sense the pre-regulator voltage (via an appropriate voltage divider).
If the pre-reg voltage drops below 5.3V then the circuit will flash a "Low Battery" indicator and disable any future water pump operation.
I am trying to save the 6V SLA battery from a harmful depletion condition.

Cheers
Barry