This Pico-based clock uses a dedicated oscillator for the built-in RP2040 RTC, displays time using seven-segment indicators, features capacitive touch-sensing buttons, and a custom built-in NiMH charging circuit.
The estimated run-time on a single charge is one week (yes, just one week).
When assembling, refer to the interactive BOM page.
---
title: Charger state machine
---
stateDiagram-v2
[*] --> Hold
Hold --> Charge: ext_power && v < HIGH
Charge --> Charged: d(v) ≤ NDV || is_adc_saturated() || is_timed_out()
Charged --> Charge: v < HIGH
Charge --> Hold: !ext_power
Charged --> Hold: !ext_power
- Add a time-out for
v ≥ NiMH_HIGH
(1–2h?)