Add support for Eufy C20

[cvoinf]

Addresses issue #1352

[cvoinf]

At the moment, weight and heartrate is measured, although the log says, the impedance is transmitted, too.

? 2026-04-20 00:16:03.241 D/openScaleLog: Initial markdown-diff headers written to: /storage/emulated/0/Android/data/com.health.openscale.debug/files/logs/openScale_current_log.txt
? 2026-04-20 00:16:03.257 D/openScaleLog: Initial markdown-diff headers written to: /storage/emulated/0/Android/data/com.health.openscale.debug/files/logs/openScale_current_log.txt
+ 2026-04-20 00:16:03.257 I/openScaleLog: File logging enabled during runtime – started fresh session log.
? 2026-04-20 00:16:31.316 D/BluetoothActionButton: User clicked bluetooth icon connect → trying to connect to saved device Debug
+ 2026-04-20 00:16:31.318 I/BleConnector: Attempting to connect to Debug
? 2026-04-20 00:16:31.319 D/BleConnector: Switching to new device: Releasing active communicator: null
? 2026-04-20 00:16:31.319 D/BleConnector: Switching to new device: Active communicator released and set to null.
? 2026-04-20 00:16:31.320 D/ScaleHandlerFactory: createCommunicator: Searching for communicator for 'Debug' (BC:0F:B7:02:31:9D). Handler hint: 'Eufy C20 (T9130)'
+ 2026-04-20 00:16:31.321 I/ScaleHandlerFactory: Modern handler 'Eufy C20 (T9130)' supports 'Debug'.
+ 2026-04-20 00:16:31.327 I/ScaleHandlerFactory: Modern communicator 'BroadcastScaleAdapter' created for 'Debug' with linkMode=BROADCAST_ONLY.
+ 2026-04-20 00:16:31.328 I/BleConnector: ActiveCommunicator successfully created: BroadcastScaleAdapter. Starting observation job...
? 2026-04-20 00:16:31.329 D/BleConnector: Adapter isConnected: false for Debug (Status: CONNECTING)
+ 2026-04-20 00:16:31.330 I/BleConnector: Adapter no longer reports connected for Debug. Current status: CONNECTING. Expecting Disconnected Event.
? 2026-04-20 00:16:31.334 D/EufyC20: attach()
? 2026-04-20 00:16:31.343 D/BleConnector: BluetoothEvent received: Listening(deviceAddress=BC:0F:B7:02:31:9D) for Debug
+ 2026-04-20 00:16:31.343 I/BleConnector: Event: Listening for broadcasts from BC:0F:B7:02:31:9D
? 2026-04-20 00:16:31.349 D/BroadcastScaleAdapter: Broadcast scan started (attempt 1/3) for BC:0F:B7:02:31:9D
? 2026-04-20 00:16:31.424 D/BroadcastScaleAdapter: Discovered advertisement from BC:0F:B7:02:31:9D RSSI=-48 payload=[02 01 06 1B FF 64 BC 0F B7 02 31 9D 00 40 54 E5 69 65 00 22 1F 00 00 00 …(+19b)]
? 2026-04-20 00:16:31.426 D/BroadcastScaleAdapter: Forwarding advertisement to handler: BC:0F:B7:02:31:9D RSSI=-48 payload=[02 01 06 1B FF 64 BC 0F B7 02 31 9D 00 40 54 E5 69 65 00 22 1F 00 00 00 …(+19b)]
+ 2026-04-20 00:16:31.434 I/EufyC20: Eufy C20 final: weight=79.7 kg hr=0 imp=464.6
+ 2026-04-20 00:16:31.434 I/EufyC20: ← publish measurement to app
? 2026-04-20 00:16:31.436 D/BleConnector: BluetoothEvent received: MeasurementReceived(measurement=ScaleMeasurement(userId=255, dateTime=null, weight=79.7, fat=0.0, water=0.0, muscle=0.0, visceralFat=0.0, bone=0.0, lbm=0.0, bmr=0.0, heartRate=0, impedance=464.6), deviceAddress=BC:0F:B7:02:31:9D) for Debug
+ 2026-04-20 00:16:31.437 I/BleConnector: Event: Measurement received from Debug: Weight 79.7
+ 2026-04-20 00:16:31.437 I/BleConnector: (Debug): Saving measurement for App User ID 1.
? 2026-04-20 00:16:31.438 D/BroadcastScaleAdapter: Handler returned CONSUMED_STOP for BC:0F:B7:02:31:9D
? 2026-04-20 00:16:31.439 D/BroadcastScaleAdapter: Measurement stabilized → BroadcastComplete for BC:0F:B7:02:31:9D

[cvoinf]

impedance is still seldomly transmitted and if transmitted, not analysed.
openScale_current_log (3).txt

[cvoinf]

Could it be that openscale doesn‘t read the impedance?
Perhaps we have to use these algorythms: https://github.com/dckiller51/bodymiscale/blob/main/custom_components/bodymiscale/metrics/impedance.py

Bodymiscale uses Xiaomi (Legacy 2017) formulas to derive metrics.
Legacy Mode: Uses the original 2017 formulas (ideal for historical consistency).
Scientific Mode: A new, more precise calculation mode for BMR and Body Composition, specifically tuned for active profiles.

[cvoinf]

Ah, I found exactly these formulas in com.health.openscale.core.bluetooth.libs.MiScaleLib. Now I added ScaleMeasurement as in MiScaleS400Handler, and everything works as expected.

[cvoinf]

Transmission is only sometimes possible. It seems the time between first handshake and heatrate-measurement has to be as small as possible. Thus if openscale is opened when the measurement of the heartrate starts results in successful transmission most of the time (set auto-connection of scale to true)

Any ideas?

[oliexdev]

You could add here a parameter tuningProfile where you can set a pre-config BLE tuning profile or you can even set a custom profile with your scale specific settings, see ModernScaleAdapter what you can set.

[oliexdev]

Thanks for your PR 👍
You could add a BLE tuningProfile where you can set a pre-config tuning profile or you can even set a custom profile with your scale specific settings, see ModernScaleAdapter which parameter can be set.