feat: add support for Taylor 5331891 #1393
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Adds TaylorBIAHandler for the Taylor Body Composition Bathroom Scale (advertised as "5331891 BIA Scale"). The scale exposes service 0xFFB0 (FFB1 write, FFB2 notify), the same GATT layout as the MGB family, so MGBHandler previously mis-claimed it and the session timed out with no measurement because the notification format differs. Protocol (reverse-engineered from btsnoop HCI logs): - 20-byte NOTIFY frames "AC 27 <flag> <chan> <hi> <lo> ... 24 D5 <cksum>". - weight_kg = (((chan & 0x01) << 16) | (hi << 8) | lo) / 1000.0, where the channel byte's low bit is weight bit 16 (0x8C < 65.536 kg, 0x8D >= 65.536 kg). - flag 0x80 = stable, 0x01 = summary record. Verified against two captures (171.2 lb and 173.0 lb readings). The scale transmits weight only; body composition is computed app-side by the vendor and is not exposed over BLE, so only LIVE_WEIGHT_STREAM is implemented. TaylorBIAHandler is registered ahead of MGBHandler in ScaleFactory (first non-null supportFor wins). Includes unit tests for the weight decode. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Under openScale's minimal init the scale never sends an explicit stable (0x80) or summary (0x01) frame; it streams live values that plateau. The previous code published only via a flat fallback timer, which could capture a still-settling value. Publish instead when the same weight repeats STABLE_FRAMES (4) times in a row (~1s at the scale's ~4Hz stream) — the settled value repeats verbatim while step-on ramp values are all distinct. Explicit stable/summary frames are still honored, and a last-resort timer (FALLBACK_DELAY_MS) covers weight that never settles. Verified on device: records 77.65 kg = 171.2 lb. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Add support for Taylor 5331891 BIA Scale
Scale
Taylor Body Composition Bathroom Scale (model 5331891) — shows up on Bluetooth as
5331891 BIA Scale.Summary
This PR adds a dedicated
TaylorBIAHandler. Because this scale uses the same Bluetooth service (0xFFB0) as the MGB scale family, our app used to accidentally let theMGBHandlerclaim it. That caused the connection to time out without getting a measurement, as Taylor's data format is entirely different.What works: Live and stable weight (tested against real measurements).
Not implemented: Body composition (explained below).
Protocol (reverse-engineered)
0xFFB0.weight_kg = (((chan & 0x01) << 16) | (hi << 8) | lo) / 1000.080 8D ...→ 68.200 kg = 150.4 lb;80 8D ...→ 69.500 kg = 153.2 lb (which perfectly matches the official app's readout).Publishing the final reading
Most of the time, the scale doesn't send a specific "done" signal, it just continuously streams live weight values until the user stands still and the numbers plateau. To handle this, I added a stability check: once the weight stays exactly the same for 4 readings in a row (about 1 second), it's locked and published. The handler will still honor explicit "stable" signals if they ever arrive, and there's a fallback timer just in case the weight never fully settles.
No body composition
The scale only ever sends weight, there is no body impedance data sent over BLE. The official Precision Hub app "calculates" body fat, water, and muscle by itself, which probably means that the stats are bullshit anyway. Since there's no access to those formulas or the raw impedance data over Bluetooth, body comp cannot be reproduced here.
Changes
core/bluetooth/scales/TaylorBIAHandler.kt.ScaleFactory.ktto check for the Taylor scale before the MGB scale, ensuring the right handler picks it up first.TaylorBIAHandlerTest.ktto verify the weight decoding logic (including idle states and bit-boundary cases).Testing
AI Disclaimer