Merge RAK4631 PMU logic from CE firmware + button change

[metrafonic]

The liberatedsystems/RNode_Firmware_CE has some PMU/Battery logic for the RAK4631. The voltage curves probably need some tweaking.

I also switched the user button to pin 31 as this is accessible from the board without having to add an IO module. See https://store.rokland.com/pages/adding-a-user-button-rak19007 for details.

Built and confirmed running on my own RAK4631

[markqvist]

Great stuff, this is looking good! I'll merge this in before the next release! Thanks for the contribution!

[ghost]

I also switched the user button to pin 31 ...

That's a good idea, but what's the deal with the users using IO adapters?
Should they all take apart their devices and resolder the already functioning buttons? Or does that work too?

[metrafonic]

@memo-567 you have a valid point, however it seems redundant to use an IO module to expose a single pin (there are no other uses for the IO on an RNode). It feels more "correct" to have this as the default

Maybe in the future we could have rnodeconf specify the user pin. It likely applies in a similar way to a lot of boards.

[metrafonic]

I also noticed today that the RAK does not have the sleep logic implemented. Ill try add that too

[markqvist]

Hmm, there's some good points here. If some people are already using the IO module as default, this should probably be a configurable option with rnodeconf. Would not be too hard to add that.

[metrafonic]

Sleep now sets the display backlight to zero, disables external peripheral power, and sleeps the MCU.
There was no logic to enable external peripheral power, so i added that. I do not think it is required, maybe useful for gps, powering other devices etc.

Testing:
I have a super cheap USB power meter, the current goes from 0.02A to 0.00A when sleeping. I will confirm with a multimeter later.

It would be nice if someone could verify that it works for them too. I've attached my build.

rnode_firmware_rak4631.zip

[markqvist]

Good stuff. I don't really have much RAK hardware to test with here, so hopefully someone else can jump in and check it out.