VBAT on A15 instead of AUX4

[Nicksdesign]

I have a 2560 board that doesn't have A0 brought out. I'm not using AUX4 on A15 and would like to us A15 for VBAT. I've been able to connect a voltage divider to A15 and assigned the VBAT function to it: #define OVERRIDE_V_BATPIN A15. I've adjusted the VBATSCALE up and down, and around again. Every time I get the scale factor correct for one voltage it's wrong for different voltage. Clearly there is still a current source/sink (pull up resister?) on A15 left over from using it as an input.

Any help to fix this would be greatly appreciated. I've hit a wall.

Nick

[Nicksdesign]

I now know more even though the result is still not what it should be. The Vbat reassignment works and it does not appear that there is a pullup resister enabled. There is just another problem of some sort.

Since this may be a software issue, I'm going to start another thread in the software sectionl.

Nick