Steambattery

Battery monitoring for the Steam Controller 2 ("Triton") on Linux: a daemon that reads battery telemetry straight from the controller's HID reports, and a COSMIC panel applet that displays it.

Supports all three transports: the puck dongle, direct USB, and Bluetooth LE.

The kernel's hid-steam driver doesn't (yet) support the SC2 family, so nothing shows up in UPower — this fills the gap in userspace.

• daemon/ — steambatteryd: discovers SC2 devices (wired 28de:1302, Bluetooth 28de:1303, puck dongle 28de:1304) via udev, reads battery reports from hidraw, and publishes state on the session D-Bus.
• applet/ — cosmic-applet-steambattery: panel icon + percentage, with a popup showing charge state, voltages, currents, and temperature.
• interface/ — steambattery-interface: the shared D-Bus contract (constants, ChargeState, and zbus client proxies for third parties).

Protocol

The controller pushes input report 0x43 (TritonBatteryStatus_t, from SDL3's controller_structs.h) roughly every 2.5 s while awake — no query needed. Units were calibrated against live hardware: voltages in mV, currents in mA, temperature in milli-°C. The controller-state stream (0x42, or 0x45 over Bluetooth; ~266 Hz) doubles as a liveness signal; 10 s of silence marks the controller asleep/disconnected.

Protocol research: CouchTurtle/sc2-research and the SDL3 Triton driver.

Install (NixOS)

# flake inputs
inputs.steambattery.url = "github:eva-val/steambattery";

# NixOS configuration
imports = [ inputs.steambattery.nixosModules.default ];
hardware.steambattery.enable = true;

The module installs:

• a udev rule granting local users access to SC2 hidraw nodes (via the users group plus uaccess),
• a systemd user service running steambatteryd,
• the applet package with its desktop entry.

Then add the applet: COSMIC Settings → Desktop → Panel → Configure panel applets → Add applet → "Steam Controller Battery".

D-Bus interface

Session bus name io.github.steambattery.

• /io/github/steambattery — io.github.steambattery.Daemon
  • Devices: ao — device object paths
  • Version: s
• /io/github/steambattery/devN — io.github.steambattery.Device
  • Name: s, Connected: b
  • ChargeState: y — SDL3 EChargeState: 0 reset, 1 discharging, 2 charging, 3 charger-validate, 4 done (2 and 3 mean "charging")
  • BatteryLevel: y — 0–100, 255 = no report yet
  • BatteryVoltage, SystemVoltage, InputVoltage: q — mV
  • Current, InputCurrent: q — mA
  • Temperature: q — milli-°C
  • LastUpdated: t — unix seconds of the last published change, 0 = never (telemetry is deadbanded, so while Connected is true the data is live even if this is a little stale)

All properties emit PropertiesChanged. Quick check:

$ busctl --user get-property io.github.steambattery \
    /io/github/steambattery/dev0 io.github.steambattery.Device BatteryLevel
y 100

Development

$ direnv allow        # or: nix develop
$ cargo test
$ cargo run -p steambatteryd                   # needs hidraw access (udev rule)
$ cargo run -p cosmic-applet-steambattery      # runs standalone as a window

License

GPL-3.0-or-later.