feat(rak3401): AIN1 button for status screen and shutdown

[dorfman2]

AIN1 Button for Status Screen and Shutdown (RAK3401) 🤖🤖

Adds physical button support on AIN1 (pin 31) for the RAK3401 1W repeater, designed for use with a 3D printed portable case that incorporates an Omron-style limit switch as a user button.

Note from the Human: I combined these two feature into to a single PR, but am happy to split this out and discuss further. This is a specific use case where a repeater is being deployed at a festival, and isn't "set & forget." I do think switch functionality could be inherent on this board, as long as we maintain the normally open logic, similar to the OLED screen (always on, but doesn't always physically exist).

Button Actions

• 0.5s hold → Status screen (uptime, battery voltage, percentage, gauge bar, charging indicator)
• 5s hold → Graceful shutdown with "Shutting down..." message, then NRF52 SYSTEMOFF
• Press while off → Wake from SYSTEMOFF via GPIO SENSE

Screenshots

Home Screen	Status Screen	Final Hardware Build

NOTE: Screen does auto-off to save power as in the current code, but uploading photos of the screen black is decidedly not helpful.

UI Changes

• Redesigned repeater screens with angular theme for small OLEDs
• Inverted header bars, horizontal rule separators, label:value layout
• Full-width battery gauge bar with percentage
• Charging indicator (plug icon + "CHG") when USB power detected via isExternalPowered()

Hardware Changes

• PIN_USER_BTN_ANA=31 build flag for RAK_3401_repeater
• Public powerOff() override on RAK3401Board delegating to initiateShutdown(SHUTDOWN_REASON_USER)
• GPIO SENSE LOW wake configured on AIN1 before SYSTEMOFF
• Waits for button release before entering SYSTEMOFF to prevent immediate wake

Notes

• Uses digitalRead instead of analogRead — nRF52 SAADC disconnects INPUT_PULLUP during conversion
• Battery percentage: linear mapping 3.0V (0%) → 4.2V (100%) for single-cell 3.7V LiPo
• UI changes are in examples/simple_repeater/UITask.* which affects all repeater variants

Case Design

https://www.printables.com/model/1627139-case-for-rak-wisblock-1-watt-starter-kit

Made as a portable case for the RAK Wisblock 1 Watt starter kit. This case accommodates a very large battery (10000mAh or 15000mAh, 60mm x 110mm x 10mm) and incorporates a standard 128x64 OLED screen, standard micro toggle for power, an Omron style limit switch for user button, and two SMA antenna holes.

[ripplebiz]

Nice work.
Just a small one, can you adjust the alignment of the SF and CR values. Looks like '8 CR' is associated, instead of '8' being associated with 'SF':

[dorfman2]

Nice work. Just a small one, can you adjust the alignment of the SF and CR values. Looks like '8 CR' is associated, instead of '8' being associated with 'SF':

Yes I can! Should be pushed shortly.

[dorfman2]

Label Alignment complete.

• There were also a minor change to make battery min/max for the display adjustable during build (default 4200mV, no local override). It gives me hives to never reach 100% charge, as my battery tops out at 4.18v 😁 .
• I can pull this out if you want, since this would qualify as feature creep.

How it works:

• By default, every board gets 3000mV–4200mV (standard single-cell LiPo range)
• If a board needs different values (different battery chemistry, charging circuit caps at a lower voltage, etc.), they add -D BATT_MAX_MILLIVOLTS=4100 to their platformio.ini build flags
• The -D flag defines the macro at compile time before the #ifndef check, so the default is skipped

Why it matters:

• Not all charging circuits charge to 4.2V — some cap at 4.1V or 4.0V for longevity
• Some setups use LiFePO4 cells (3.6V max) or dual-cell packs
• This is the same pattern the companion radio already uses for its battery indicator

For this PR, the defaults stay at 3000/4200 so nothing changes for existing users. Any board variant can override via a single build flag line.

[dorfman2]

Follow-up: dropped the battery threshold build flags
Force-pushed a new HEAD to remove the #ifndef BATT_MIN_MILLIVOLTS / BATT_MAX_MILLIVOLTS guard block that was in
UITask.cpp
. The calculation is back to the original 3000/4200 mV literals.

Why: the CLI already exposes runtime tuning for the battery reading, so a compile-time override was duplicating existing functionality.

From the MeshCore CLI docs:

Fine-tune the battery reading

• get adc.multiplier
• set adc.multiplier <value> (range 0.0–10.0, default 0.0 = board-defined)
• Returns Error: unsupported by this board if the hardware doesn't support it.

Net change on the branch:

• 8482a098 (mixed: SF/CR alignment + battery guards) → 71ae7839 (SF/CR alignment only, cleaner message).
• Build still clean on RAK_3401_repeater, flash size unchanged.

The AIN1 button feature itself is untouched.

[dorfman2]

@ripplebiz Wanted to check back in on merging this. If you don't think it's helpful, I can close this.