I checked the battery and it is installed correctly. I also pulled the power and left it for 5 minutes, and when powered back up it had kept all my configuration, so it does seem to be working OK just not measured properly for some reason.
If you have pulled AC and also main battery, and still config is kept after 5 minutes. Then the battery is fine as well as RTC and Backup SRAM.
Why it is not measuring I have no idea, it is internall logic of MCU. You can checked in zone thread.
Uff, there are more mistakes in this part, since F437 has build in 1/4 divider instead of 1/2 divider in F407/F417.
I wonder what my gateway measure :) really. There is slight voltage drop on the schottky protection diode, which correspond to my real battery voltage measured and the voltage on web.
I've pushed some changes but have test it also on my side.
Hi Adam, I will check load the new image and check. I have been thinking a bit about this and planned to take the case apart and remove the PCB for some more detailed testing.
I will let you know about the new image.
You can ceck if the voltage go to the MCU pin VBAT with multimeter, there is near by capacitor.. But if you unplugged AC and main battery, and still the configuration is kept, then all on PCB is fine, no need to check.
Rest is inside MCU.
There's not to much more in the datasheet. However I found that measuring internal temperature requires more sampling time. Now the ADC IN18 is shared between Vbat and temp. So I've increased the sample time to max for Vbat. Now it shows for me back reasonable voltage:
RTC battery 2.77 V
Pushed new commit, you may try on your side.