Battery Voltage correct in APM Planner - Incorrect in MP

Thank you for taking time to review my problem. I’m a mechanical person so please lend me some grace for any ignorance.

While researching my problem I found that most causes for bad voltage readings in Mission Planner are due to incorrect power module configuration. In my situation, Mission Planner battery voltage is showing 0 for every power module configuration I’ve tried, even “Other” custom config, but in APM Planner battery voltage shows correctly. APM Planner has “APM 2.5/6 Power Module” as a battery monitor preset and this selection reports battery voltage correctly in APM Planner but not MP. When I measure the battery voltage pin from the power module on the APM CCA and multiply by the BAT_VOLT_MULT, I get the correct battery voltage. Hardware seems to be working correctly.

My hunch - MP is not recognizing the pin assignments for my hardware, as the pin assignments listed are not in the current Copter documentation. Specifically, BATT_VOLT_PIN = 13. Did we lose support for atmega MC at some point? It’s worth noting that, while I can get the current to read correctly in MP, the field of the dropdown box for “Battery Current sensing pin” in the Standard Parameters tab of MP is blank. If I choose any of the options from there current is reported grossly high.

Setup:
Atmega2560 APM board (hardware ver 2.8)
RCTimer power module (old but works fine)
ArduCopter V3.2.1
RFD SiK 1.9 on HM-TRP (both air and ground)
MP ver 1.3.79
APM Planner V2.0.26

Setup that works in APM Planner
BATT_MONITOR 4
BATT_VOLT_PIN 13
BATT_CURR_PIN 12
BATT_VOLT_MULT 10.2
BATT_AMP_PERVOLT 24
BATT_AMP_OFFSET 0
BATT_CAPACTIY 6000
BATT_VOLT2_PIN -1
BATT_VOLT2_MULT 1

0-0-1_2023-01-08.param (5.8 KB)
0-0-2_2023-01-08.param (5.0 KB)

Anyone know what is going on here? I prefer to use MP over APM Planner if possible.

I think you are correct in assuming MissionPlanner is not fully aware of your hardware.
With that early non-supported APM board you will have to continue using APM Planner, or find a very early version of MissionPlanner. You will have very limited support, if any at all.
Or throw it away and get something supported. There are so many more features and improvements now, and people here will be able to help.

Thanks for the reply. This is for an old project I’ve had sitting around. I would hate to throw away something that works just because it’s old. I’ll just wrestle around with compatibility for now. I hope it flies ok.