openble-lifesense

The Lifesense A2/A3 Bluetooth weight-scale protocol, as spoken by the Philips DL8780 and other scales built on the Lifesense SDK.

• openble.lifesense.packets: parsers for the weight (8A21, 8A24) and body-composition (8A22) packets.
• openble.lifesense.link: the 8A81 command frames, and the pair and sync handshake that makes the scale send a weigh.
• openble.lifesense.identify: matches advertisements and GATT tables to a scale.
• openble.lifesense.uuids: service and characteristic ids.

Pure Python 3.11+ with no dependencies and no Bluetooth stack. The handshake takes a write coroutine and a queue of indications, so it runs over bleak, a test double, or anything else.

pip install openble-lifesense

Parse a weigh

from openble.lifesense.packets import parse_a3_append, parse_a3_weight

weight = parse_a3_weight(
    bytes.fromhex("1f 16 26 00 fe 89 50 91 1f 00 00 00 00 17 13 00 ff 01 19 00")
)
weight["weight_kg"], weight["impedance"], weight["date"]
# ('97.5', '488.7', '2026-10-13 19:50:33')

append = parse_a3_append(
    bytes.fromhex("6d 89 50 91 1f 01 fc f0 32 f2 79 f1 26 f0 00 00 00 00 00 00")
)
append["body_fat_ratio"]
# '25.2'

parse_scale_notification(short, data, family=..., previous=...) picks the parser the Lifesense dispatcher would use for a characteristic. identify.protocol_digit(service_uuids) gives the family.

Pair and sync with bleak

The scale sends a 0xA0 password when it is in pairing mode (hold the unit button for 3 s) and a 0xA1 random when it is already paired. run_scale_handshake answers either one. It stores the password and broadcast id in a ScaleStore JSON file, and it needs that same file for every later sync.

import asyncio
from pathlib import Path

from bleak import BleakClient
from openble.lifesense.link import ScaleStore, run_scale_handshake
from openble.lifesense.packets import parse_a3_weight
from openble.lifesense.uuids import sig


async def weigh(address: str) -> None:
    commands: asyncio.Queue[bytes] = asyncio.Queue()
    async with BleakClient(address) as client:
        await client.start_notify(
            sig("8a24"), lambda _, data: print(parse_a3_weight(bytes(data)))
        )
        await client.start_notify(
            sig("8a82"), lambda _, data: commands.put_nowait(bytes(data))
        )

        async def write(payload: bytes) -> None:
            await client.write_gatt_char(sig("8a81"), payload, response=True)

        await run_scale_handshake(
            write=write,
            queue=commands,
            store=ScaleStore(Path("scale.json")),
            device_key=address,
            user_number=1,
            user_name="User",
            password_override=None,
            listen_seconds=60,
            log=lambda kind, **payload: print(payload.get("message", "")),
        )

apps/ble-probe and apps/bathroom-hub in the repository are complete clients built this way.

Protocol notes

• docs/lifesense-scale-protocol.md: the static manual, read from the Philips Health app's bytecode.
• docs/dl8780-connection-handoff.md: what worked against a live DL8780, including the HCI capture the sync sequence follows.

Not affiliated with Philips or Lifesense. The names identify the devices this interoperates with.

License

MIT License, copyright 2026 Kadima Tech.