Heimdall switch

heimdall-switch

Wireless power switch node for RC vehicles, part of the Heimdall Suite.

Controlled from heimdall-module over BLE, independent of the vehicle's normal RC control link (e.g. CRSF) — this switch has its own out-of-band radio path so it keeps working regardless of the state of the main control link. It originated as a replacement for a boat's Jeti SPS-20 magnetic switch, but is built as a generic building block (not a single-purpose commercial part like Jeti's RCPS10) so the same design serves any RC vehicle — boat, plane, car — needing a remotely switched load.

How it's triggered

flowchart LR
    TX["EdgeTX transmitter<br/>Lua widget or OneClick"]
    BTN["Local button<br/>on the switch node"]
    MOD["heimdall-module<br/>external RF module (ESP32-C3)"]
    SW["heimdall-switch<br/>nRF52 node"]
    LOAD["Switched load"]

    TX -- "S.Port" --> MOD
    MOD -- "BLE command (absolute ON/OFF)" --> SW
    SW -- "MOSFET (fail-on)" --> LOAD
    SW -- "BLE ack burst" --> MOD
    MOD -- "S.Port telemetry (ack)" --> TX
    BTN -. "5-15s: toggle, 15s+: pair" .-> SW

The transmitter side (Lua widget or a OneClick action) sends the command through heimdall-module, the external RF module in the transmitter's module bay; heimdall-module relays it over BLE to heimdall-switch, which drives the MOSFET and acks back the same path so the widget can show "Hello" / "Goodbye" / "No response". The node also has a local button for manual toggling and pairing, independent of that whole chain.

Docs

• .docs/hardware.md — MCU, power, switching stage, feedback, button/LED, open hardware items
• .docs/protocol.md — BLE roles, pairing, runtime cycle, command/ack frame layouts, the transmitter-side Lua widget
• .docs/persistence.md — what's kept in flash across power loss (state + replay counter) and the wear-levelling scheme
• .agents/AGENTS.md / CLAUDE.md — instructions for AI coding agents working in this repo
• hardware/kicad/ — first-draft KiCad schematic (see .docs/hardware.md's Schematic section for what's in it and what's still a placeholder)

Status

No firmware yet. nRF52 toolchain (nRF5 SDK vs. nRF Connect SDK/Zephyr vs. upstream Zephyr) is not yet decided. src/ is a placeholder until that's settled. A first-pass schematic exists under hardware/kicad/.