acaia-lunar-ble

Python library for interacting with the Acaia Lunar coffee scale over Bluetooth Low Energy (BLE).

Built for specialty coffee enthusiasts who want to programmatically read weight data from their Acaia Lunar scale. Uses the bleak library for cross-platform BLE support (macOS, Linux, Windows).

Note: This library is specifically built for the Acaia Lunar model only — it does not support other Acaia scales (Acaia Pearl, Pyxis, etc.). It has been tested with the Lunar 2021 (Model AL008). Models AL009 and AL010 should work as well since they share the same BLE protocol, but have not been tested.

Features

• Real-time weight streaming (stable and unstable readings)
• Timer readback and control (start, stop, reset)
• Tare command
• Battery level and scale settings (units, auto-off, beep)
• Button event notifications (tare, start, stop, reset pressed on scale)
• Scan and discover nearby Acaia scales
• Automatic heartbeat to maintain connection
• Async/await API built on bleak
• Context manager support for clean connect/disconnect

Installation

pip install acaia-lunar-ble

Quick Start

import asyncio
from acaia_lunar_ble import ScaleConnection


def on_weight(weight: float):
    print(f"Weight: {weight:.2f} g")


async def main():
    scale = ScaleConnection("YOUR-SCALE-ADDRESS", weight_callback=on_weight)

    if not await scale.connect():
        print("Failed to connect")
        return

    await asyncio.sleep(30)  # read weights for 30 seconds
    await scale.disconnect()


asyncio.run(main())

Finding Your Scale's Address

If you don't know your scale's BLE address, use the built-in discovery:

import asyncio
from acaia_lunar_ble import ScaleConnection


async def main():
    acaia_devices, all_devices = await ScaleConnection.discover()
    for d in acaia_devices:
        print(f"{d.name}: {d.address}")
    if not acaia_devices:
        print("No Acaia scales found. All nearby BLE devices:")
        for d in all_devices:
            print(f"  {d.name or '(unknown)'}: {d.address}")


asyncio.run(main())

Example Script

An interactive example script is included in examples/demo.py:

python examples/demo.py <SCALE-ADDRESS>

Interactive commands during the session:

Weight and timer readings update in real-time. Type a command letter and press Enter. Press q + Enter to quit, or Ctrl+C.

Context Manager

For automatic cleanup, use async with:

async with ScaleConnection(address, weight_callback=on_weight) as scale:
    await asyncio.sleep(60)  # stream weights for 60 seconds
# automatically disconnects when exiting the block

API Reference

ScaleConnection(address, *, ...)

Main class for interacting with the scale.

Constructor parameters:

• address — BLE address (MAC or UUID) of the scale
• weight_callback — called with each weight reading in grams (float)
• timer_callback — called with timer value in seconds (float)
• battery_callback — called with battery percentage (int, 0-100)
• settings_callback — called with a ScaleSettings object (battery, units, auto-off, beep)
• button_callback — called with button name (str): "tare", "start", "stop", or "reset"
• notification_callback — called with every raw BLE notification payload (bytearray)

Methods

Properties

ScaleSettings

Dataclass with fields: battery (int), units (str), auto_off_minutes (int), beep (bool).

decode_weight(data)

Standalone function to decode a BLE notification payload into a weight value in grams. Returns None if the data doesn't match the expected format.

Protocol Details

The Acaia Lunar uses a proprietary BLE protocol. Communication happens over two GATT characteristics:

• Write characteristic (49535343-8841-43f4-a8d4-ecbe34729bb3) — used for sending commands (identify, notification request, heartbeat)
• Notify characteristic (49535343-1e4d-4bd9-ba61-23c647249616) — streams weight and other data from the scale

The initialization sequence must follow this exact order:

1. Subscribe to notifications
2. Send IDENTIFY handshake
3. Send NOTIFICATION_REQUEST to enable data streaming
4. Start heartbeat loop (~3 second interval)

Requirements

• Python 3.10+
• Bluetooth Low Energy hardware
• bleak (installed automatically)

License

MIT