wiight

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Table of Contents

• Installation
• Configuration
• Pairing
• Calibration
• Measurement
• Capture
• MQTT Service
• Raspberry Pi Deployment
• License

Installation

pip install wiight

Install the optional MQTT transport for service operation:

pip install 'wiight[mqtt]'

Linux hardware access additionally requires BlueZ, the kernel hid-wiimote driver, libxwiimote, and its Python binding.

Configuration

The service configuration defaults to /etc/wiight/wiight.toml:

[board]
address = "00:22:4C:60:0C:DB"
# adapter = "hci0"

[measurement]
minimum_weight_centikilograms = 1000
stable_duration_seconds = 2.0
maximum_stddev_centikilograms = 50
unload_threshold_centikilograms = 500

[calibration]
path = "/var/lib/wiight/calibration.json"
minimum_samples = 100
maximum_corner_stddev_centikilograms = 10

[mqtt]
host = "mqtt.local"
port = 1883
client_id = "wiight"
base_topic = "wiight/scale"
discovery_prefix = "homeassistant"
tls = false

Validate configuration without accessing Bluetooth hardware:

wiight config-check --config /etc/wiight/wiight.toml

MQTT credentials are intentionally not accepted in this file. Supply them through the service environment or systemd credentials when MQTT support is configured. Tare calibration is stored as versioned JSON bound to the board's Bluetooth address; calibration from another board is rejected.

Pairing

Press the balance board's red sync button, then pair and connect the configured board through BlueZ:

wiight pair --config /etc/wiight/wiight.toml

Discovery and pairing share a 30-second deadline by default; use --timeout to change it. The command is restricted to the configured board address and adapter. Wiight deliberately does not register a pairing agent because the Nintendo PIN contains binary adapter-address bytes that cannot be represented reliably by the Agent1 string API. BlueZ's built-in Wii autopair plugin must be enabled to supply that PIN.

Calibration

Initial tare calibration is optional. Without a calibration file, measure and the MQTT daemon use zero offsets and report the board's kernel-provided, factory-calibrated centikilogram values. MQTT status reports "calibrated": false in this mode.

To remove the board's current empty-load offset, place it on a firm surface with nothing touching it, then run:

wiight tare --config /etc/wiight/wiight.toml

The command collects the configured number of stable empty-board samples and atomically writes the resulting per-corner offsets to the configured calibration path. It fails without replacing the existing calibration if the board is too unstable or too few samples arrive before the bounded capture ends.

If a calibration file exists but is corrupt, incompatible, or belongs to a different board, startup fails instead of silently falling back to zero offsets.

Measurement

Measure one stable weight, using persisted tare when available:

wiight measure --config /etc/wiight/wiight.toml

Use --json for machine-readable JSON Lines. Use --continuous to emit another measurement after the board has been unloaded and occupied again. --timeout and --idle-timeout bound the session and event wait respectively.

By default, tare and measurement require the configured Bluetooth address to be connected in BlueZ, optionally scoped to the configured adapter, and require exactly one balance board to be available through xwiimote. If multiple boards are connected, provide the intended xwiimote sysfs path with --device. Supplying --device is an explicit diagnostic override and bypasses configured Bluetooth-address matching.

Capture

Record a bounded hardware trace as JSON Lines:

wiight capture --duration 10 --output board.jsonl

Use --idle-timeout to control how long capture waits without an xwiimote event. Use --device when more than one balance board is connected. Each sample contains wall-clock and monotonic timestamps, the xwiimote event type, four corner values ordered as top-left, top-right, bottom-right, bottom-left, and the total. Sensor values are centikilograms.

Capture files can contain personal weight data. Do not commit them unless they have been intentionally anonymized for use as test fixtures.

MQTT Service

Run the foreground service, suitable for supervision by systemd:

WIIGHT_MQTT_USERNAME=wiight \
WIIGHT_MQTT_PASSWORD=secret \
wiight daemon --config /etc/wiight/wiight.toml

The daemon publishes retained Home Assistant device discovery, retained availability and status, and non-retained stable weight measurements at QoS 1. The MQTT client configures a retained offline last will and flushes a graceful offline update before disconnecting. Corner samples are not published. Hardware access runs in a dedicated worker with bounded sample buffering, while stable measurement detection and publishing remain in the service thread.

After publishing a stable weight, the service closes the xwiimote interface and asks BlueZ to disconnect the board to conserve its batteries. The service stays online and periodically asks BlueZ to restore the paired board's HID profile. Pressing the board's front button makes it available for that reconnect.

Home Assistant discovery includes a Pair button. Press the balance board's red sync button, then press Pair within 30 seconds. The same operation can be requested by publishing the exact payload PAIR at QoS 1, without retain, to wiight/scale/pair/set (relative to the configured base topic). Retained JSON status is published to wiight/scale/pair/status with the states idle, pairing, paired, or failed.

Home Assistant discovery also includes a Tare button. Unload the board before pressing it, or publish the exact payload TARE at QoS 1, without retain, to wiight/scale/tare/set. The daemon collects the configured number of samples, applies the configured corner noise limit, atomically replaces the persisted calibration, and uses it immediately. Retained JSON status is published to wiight/scale/tare/status with the states idle, taring, tared, or failed.

Pairing is restricted to the configured board address and adapter. BlueZ's built-in autopair plugin recognizes Nintendo RVL-WBC-01 and supplies the adapter address as the Wii protocol's binary PIN. Wiight does not register an Agent1 because its string return value cannot safely carry that PIN. Restrict publish access to the pair and tare command topics with broker ACLs.

Raspberry Pi Deployment

The supported deployment target is Raspberry Pi OS Trixie with CPython 3.13. Install BlueZ, libxwiimote, the hid-wiimote kernel driver, and a Python 3.13 xwiimote binding from system packages or their upstream sources before creating the application environment. The native binding is not installed from PyPI.

From a source checkout, install the service into a system-site-packages-enabled virtual environment so it can see the native binding:

sudo python3.13 -m venv --system-site-packages /opt/wiight/venv
sudo /opt/wiight/venv/bin/pip install '.[mqtt]'

Install the service account, state directory, configuration, credentials, and unit supplied under deploy/:

sudo install -m 0644 deploy/wiight.sysusers /usr/lib/sysusers.d/wiight.conf
sudo install -m 0644 deploy/wiight.tmpfiles /usr/lib/tmpfiles.d/wiight.conf
sudo systemd-sysusers /usr/lib/sysusers.d/wiight.conf
sudo systemd-tmpfiles --create /usr/lib/tmpfiles.d/wiight.conf

sudo install -d -m 0750 -o root -g wiight /etc/wiight
sudo install -m 0640 -o root -g wiight \
	deploy/wiight.toml.example /etc/wiight/wiight.toml
sudo install -m 0600 -o root -g root \
	deploy/wiight.env.example /etc/wiight/wiight.env
sudo install -m 0644 deploy/wiight.service /etc/systemd/system/wiight.service

Edit the board address, broker settings, and credentials. The board can be paired through BlueZ before startup or from the MQTT Pair button after startup. Optionally initialize tare as the service user, then start the daemon:

# Optional:
sudo -u wiight /opt/wiight/venv/bin/wiight tare \
	--config /etc/wiight/wiight.toml
sudo systemctl daemon-reload
sudo systemctl enable --now wiight.service
sudo journalctl -u wiight.service -f

The unit runs without privilege escalation, keeps /etc/wiight read-only, and permits writes only to /var/lib/wiight. Membership in the input group is included for systems where the xwiimote devices require it.

License

wiight is distributed under the terms of the MIT license.