Renpho ES-CS20M BLE

This package provides an unofficial interface for interacting with Renpho's ES-CS20M scale (and other Renpho scales that share the same QN-series protocol) over Bluetooth Low Energy. It also has experimental, weight-only support for a broadcast-only ES-CS20M subvariant that speaks a different protocol. See the Device compatibility section for the current list of confirmed-working models.

Disclaimer: This is an unofficial, community-developed library. It is not affiliated with, endorsed by, or connected to Renpho, its parent companies, subsidiaries, or affiliates. The official Renpho website can be found at https://www.renpho.com. "Renpho", "ES-CS20M", and other model names referenced here, along with related marks, emblems, and images, are property of their respective owners. Use of any trade name or trademark is for identification and reference purposes only and does not imply any association with the trademark holder.

Features

• Live weight and body fat readings from the scale's notification stream.
• Guest-mode protocol — coexists safely with users registered by the official Renpho app on the same scale.
• Three modes: fixed-user (with Profile), user-detection (with async resolver), and weight-only.
• BodyMetrics derives 9 body-composition metrics from a stable reading: BMI, fat-free mass, body water %, skeletal muscle %, muscle mass, bone mass, protein %, BMR, and a body fat % passthrough.
• Experimental: weight-only support for the broadcast-only ES-CS20M subvariant via RenphoAABBScale (no body composition — see Device compatibility).

Installation

pip install renpho-escs20m

PyPI uses the hyphenated name renpho-escs20m; the import name uses underscores: import renpho_escs20m.

Device compatibility

The library speaks up to three Renpho BLE protocols; what a scale supports depends on which one its hardware uses:

Protocol support at a glance

Identifying your scale

Which protocol a scale speaks doesn't track the marketed model name: several Renpho models share the QN-series hardware, while some ES-CS20M hardware revisions speak a different (broadcast-only or not-yet-supported) protocol. The reliable discriminator is the HVIN (Hardware Version Identification Number) printed on the regulatory sticker on the back of the scale, including its trailing revision code (e.g. …MA2 vs …MB2 vs …MN). Some stickers don't print HVIN as a separate field — in that case the same identifier is embedded as the trailing portion of the FCC ID (e.g. FCC ID 2A26P-ESCS20M → device code ESCS20M). The FCC ID column below lets you match on either.

Some stickers don't print the HVIN as a separate field; in that case the same code is often embedded in the trailing portion of the FCC ID (e.g. 2A26P-ESCS20MA2). The tables below list both.

Confirmed-working (QN-series):

Experimental — broadcast subvariant (weight only):

One ES-CS20M subvariant (FCC ID 2APXUES-CS20M) is non-connectable — it broadcasts weight in its BLE advertisements rather than over a GATT connection, using a different (0xaabb) protocol. The library has experimental, weight-only support for it via RenphoAABBScale:

Known-incompatible — 0x55aa (not yet supported):

The Protocol column records the first bytes of the notification frames each unsupported variant emits — a rough fingerprint of the (different) BLE protocol it speaks, kept for reference and possible future support work.

The pattern so far: marketed model name is unreliable, but the HVIN — and specifically its revision suffix (A2, B2, N…) — tracks the actual hardware and apparently also the protocol. If your Renpho scale HVIN ends in A2 or N, this library will likely work with it; if it ends in some other suffix, try it out to see if it works and report back on the issue tracker.

This library may also work with other QN-Scale varieties utilizing the same protocol, including non-Renpho ones. Feel free to report compatibility results on the issue tracker.

Reporting a compatibility result

If your scale isn't in either table, open an issue at github.com/ronnnnnnnnnnnnn/renpho-escs20m/issues with:

• Marketed model (e.g., ES-CS20M)
• HVIN from the back-of-device sticker (including the revision suffix)
• Whether the library actually drives the scale correctly (live weight notifications, body fat values, etc.)

The library itself doesn't gate or warn on compatibility at runtime — it'll attempt the handshake against any device. This section is the canonical compatibility record.

Quick start

Weight only (no body fat)

import asyncio
from renpho_escs20m import RenphoQNScale, ScaleData, WEIGHT_KEY, WeightUnit


def notification_callback(data: ScaleData):
    print(f"weight={data.measurements[WEIGHT_KEY]} kg")


async def main():
    scale = RenphoQNScale(
        'XX:XX:XX:XX:XX:XX', notification_callback, WeightUnit.KG,
    )
    await scale.async_start()
    await asyncio.sleep(30)
    await scale.async_stop()


asyncio.run(main())

Fixed user + body metrics

import asyncio
from renpho_escs20m import (
    BODY_FAT_KEY, BodyMetrics, Profile, RenphoQNScale,
    ScaleData, Sex, WEIGHT_KEY, WeightUnit,
)


PROFILE = Profile(
    sex=Sex.Male,
    age=35,
    height_m=1.80,
    athlete=False,
    algorithm=0x04,        # see "Body fat algorithm" below
)


def notification_callback(data: ScaleData):
    weight = data.measurements.get(WEIGHT_KEY)
    body_fat = data.measurements.get(BODY_FAT_KEY)
    if weight is not None and body_fat is not None:
        m = BodyMetrics(
            weight_kg=weight,
            height_m=PROFILE.height_m,
            age=PROFILE.age,
            sex=PROFILE.sex,
            body_fat_percentage=body_fat,
        )
        print(
            f"weight={weight} kg  bmi={m.body_mass_index}  "
            f"bf%={m.body_fat_percentage}  bmr={m.basal_metabolic_rate}"
        )
    elif weight is not None:
        print(f"weight={weight} kg  bmi={round(weight / PROFILE.height_m**2, 1)}")


async def main():
    scale = RenphoQNScale(
        'XX:XX:XX:XX:XX:XX',
        notification_callback,
        WeightUnit.KG,
        profile=PROFILE,
    )
    await scale.async_start()
    await asyncio.sleep(30)
    await scale.async_stop()


asyncio.run(main())

User detection from weight

import asyncio
from renpho_escs20m import (
    Profile, RenphoQNScale, ScaleData, Sex, WEIGHT_KEY, WeightUnit,
)


KNOWN_USERS: dict[str, Profile] = {
    'alice': Profile(sex=Sex.Female, age=34, height_m=1.65),
    'bob':   Profile(sex=Sex.Male,   age=43, height_m=1.78),
}


async def resolve_user(weight_kg: float) -> Profile | None:
    """Pick the user whose typical weight is closest to the reading.

    Real implementations would do a DB lookup, talk to a Home
    Assistant entity, etc. The callback is async so I/O won't block
    the BLE event loop.
    """
    if weight_kg < 70:
        return KNOWN_USERS['alice']
    return KNOWN_USERS['bob']


def notification_callback(data: ScaleData):
    print(f"weight={data.measurements[WEIGHT_KEY]} kg")


async def main():
    scale = RenphoQNScale(
        'XX:XX:XX:XX:XX:XX',
        notification_callback,
        WeightUnit.KG,
        profile=resolve_user,        # ← user-detection mode
    )
    await scale.async_start()
    await asyncio.sleep(30)
    await scale.async_stop()


asyncio.run(main())

The scale firmware will not start a measurement without a profile reply, so the library always sends one in response to the scale's 0x21 05 ff profile request. In detection mode it sends a bootstrap profile with algorithm=0x00 (body fat calculation disabled) so the measurement starts; on the first stable weight frame it awaits resolve_user(weight) and writes the returned profile to the scale, which then computes body fat and emits the stable-with-metrics frame. Returning None from the resolver leaves the bootstrap profile in place — the scale stays in weight-only mode for that session.

The resolver must return faster than the scale's internal body fat commit window — empirically about 2 seconds after the first stable frame. If it doesn't, the scale will finalize the measurement against the bootstrap profile (no body fat) before your resolved profile lands. If the BLE session ends while the resolver is still in flight, the library cancels the resolver task to avoid leaking work.

Broadcast variant (weight only)

The broadcast-only 0xaabb subvariant uses a different client, RenphoAABBScale — no Profile, no unit control, weight only:

import asyncio
from renpho_escs20m import RenphoAABBScale, ScaleData, WEIGHT_KEY


def notification_callback(data: ScaleData):
    print(
        f"weight={data.measurements[WEIGHT_KEY]} kg  "
        f"(scale display shows {data.display_unit.name})"
    )


async def main():
    scale = RenphoAABBScale('XX:XX:XX:XX:XX:XX', notification_callback)
    await scale.async_start()
    await asyncio.sleep(30)
    await scale.async_stop()


asyncio.run(main())

API reference

Scale client

• RenphoQNScale(address, callback, display_unit, *, profile=None, scanning_mode=BluetoothScanningMode.ACTIVE, …) — BLE scale client. The profile argument is one of:

  • a Profile (fixed-user mode),
  • a ProfileResolver (user-detection mode),
  • None (weight-only mode, default).

  clear_stored_measurements=True (default False) drains the scale's store of offline measurements — readings taken while nothing was connected — once per session. Receiving a stored reading deletes it from the scale (the protocol has no separate delete command), so enabling this hides those readings from any other client: leave it off if you also sync the scale with the official Renpho app. Drained readings are logged at debug level and discarded for now. Each flavor is queried with its own command form.

  Additional keyword arguments (adapter, cooldown_seconds, max_connect_attempts, bleak_scanner_backend, logger) are available for advanced use — see the class docstring. RenphoESCS20MScale remains importable as a backward-compatible alias for RenphoQNScale.

• callback (passed to RenphoQNScale) — invoked only on the final stable-with-metrics frame the scale emits at the end of a measurement. In user-detection mode, the earlier stable frame is used only to trigger the profile resolver and does not reach the callback. Within the frame, ScaleData.measurements always contains WEIGHT_KEY; BODY_FAT_KEY and the two RESISTANCE_*_KEY entries are present only when the scale actually produced non-zero values for them — they will be absent in weight-only mode, in user-detection mode if the resolver returned None, and any time algorithm=0x00.

• scale.battery_level — last successfully-read battery percentage (int | None). May be None until first successful read. Reliability caveat: on at least one observed unit (firmware V10.0) the scale reported a static 100 and didn't appear to decrement it as the batteries drained — reading 100% even on cells weak enough to need replacing — and exposed no other battery source over BLE. It's unknown whether other hardware revisions or firmware behave the same way, so treat a steady 100% as possibly unreliable rather than assuming it; the value is reported as-is and may be accurate on your device.

• scale.firmware_revision — last successfully-read firmware revision string (str | None). May be None until first successful read or when response is empty.

• BluetoothScanningMode — ACTIVE (default) / PASSIVE, passed via the scanning_mode kwarg. PASSIVE only takes effect on Linux (BlueZ); other platforms fall back to active.

Broadcast variant (experimental)

• RenphoAABBScale(address, callback, *, scanning_mode=…, adapter=…, bleak_scanner_backend=…, logger=…) — client for the non-connectable 0xaabb ES-CS20M subvariant. It never opens a GATT connection; it reads weight straight from the scale's BLE advertisements. Differences from RenphoQNScale:
  • ScaleData.measurements contains only WEIGHT_KEY (always kg).
  • ScaleData.display_unit reflects the unit the scale's LCD is showing (observed from the advertisement). It is read-only — the scale cannot be told to change units, and assigning display_unit is ignored.
  • No profile, no body composition (this scale does no impedance/BIA), and no battery_level / firmware_revision.
  • Weight-only, and validated against captured advertisements rather than live hardware.

Extending the library

• RenphoScale / GattScale / AdvertisementScale — the abstract base classes the concrete clients subclass (RenphoScale holds the scanner lifecycle; GattScale and AdvertisementScale are the connection-based and advertisement-based transports). Exported for adding new protocol variants.

Profiles

• Profile(sex, age, height_m, athlete=False, algorithm=0x04) — user-profile inputs the scale needs to compute body fat on-device. See Profile's docstring for the wire semantics of each field.
• ProfileResolver — type alias for the async callback used in user-detection mode: Callable[[float], Awaitable[Profile | None]]. Receives the first stable weight in kg and returns the Profile to write (or None to skip).

Measurements

• ScaleData — dataclass passed to the notification callback. Fields: name, address, display_unit, and measurements (a dict keyed by the constants below).
• WeightUnit — KG, LB, ST, ST_LB.
• Measurement-dict keys (constants importable from renpho_escs20m):
  • WEIGHT_KEY ("weight") — kg
  • BODY_FAT_KEY ("body_fat") — % (only on stable-with-metrics frames)
  • RESISTANCE_1_KEY, RESISTANCE_2_KEY ("resistance_1", "resistance_2") — bioelectrical impedance in ohms (only on stable-with-metrics frames; the two readings are typically within a couple of ohms of each other and either can be fed to calculate_body_fat()).

Body composition

• BodyMetrics(weight_kg, height_m, age, sex, body_fat_percentage) — derives body-composition metrics from a stable reading. Call it from the notification callback once a Profile is known. No athlete parameter: by the time a body fat value reaches this class, the scale's firmware has already applied the athlete adjustment. Exposes these snake_case attributes:
  • body_mass_index — BMI
  • body_fat_percentage — passthrough of the constructor input
  • fat_free_mass (kg)
  • body_water_percentage
  • skeletal_muscle_percentage
  • bone_mass (kg)
  • muscle_mass (kg)
  • protein_percentage
  • basal_metabolic_rate (kcal/day, integer)
• calculate_body_fat(weight_kg, height_m, age, sex, resistance, *, algorithm=0x04, athlete=False) — off-scale approximation of the on-device body fat formulas (algorithms 0x03 and 0x04 only). Complements BodyMetrics: BodyMetrics takes an already-computed body fat value as input, while calculate_body_fat computes one from raw impedance. The typical pairing is to feed calculate_body_fat's output into BodyMetrics when a slow user-detection lookup misses the scale's commit window and body fat needs to be recomputed from RESISTANCE_1_KEY after the fact.

Low-level

• build_user_profile_command(...) — raw command builder for the guest-mode user-profile frame the scale expects. Most callers should construct a Profile and let RenphoQNScale call this builder; use it directly only if you need to bypass the protocol state machine.

Body fat algorithm (Profile.algorithm)

Selects which on-device body fat formula the scale runs. Most callers should leave this at the default.

• algorithm=0x04 (default) and algorithm=0x03 are the two formulas Renpho's app selects from in normal use. The selection appears to depend on user region.
• algorithm=0x00 disables the on-scale body fat calculation entirely; the scale streams weight only. This is what the library uses internally during user-detection bootstrap.
• Other values (0x01, 0x02, 0x05, 0x06) are accepted by the scale but don't seem to be used by Renpho's app and aren't validated against it — treat them as experimental.

Profile.athlete=True is independent of algorithm: it switches the firmware to its athlete-tuned curve regardless of which formula is selected.

The library also ships an off-scale approximation of algorithms 0x03 and 0x04 via calculate_body_fat() — useful when the scale's body fat commit window closes before a slow user-detection lookup resolves. The other algorithms aren't currently approximated in software.

App-matching conventions

The Renpho app applies a few non-obvious transformations to profile data before running the body fat calculation. The library diverges from one and leaves the other to the caller:

1. Height precision: library passes through; app truncates to whole cm. The Renpho app truncates a 170.7 cm profile to 170 cm before running the body fat calculation. This library passes the user's exact height_m through to the scale (rounded to the nearest mm), giving slightly more precise body fat from the scale's on-device curve.
   • If you want to reproduce the Renpho app's displayed values exactly (for cross-checking), pre-truncate the call site: height_m = int(actual_cm) / 100.
2. Age is birthday-aware. For a profile whose UI age shows N, the app uses N if the birthday has already occurred this year, else N − 1. Profile.age is a plain integer — callers wanting to match the app should compute this themselves before constructing the Profile.

Platform compatibility

• Python 3.11+
• bleak 2.x or 3.x (bleak>=2.0.0,<4.0.0)
• Tested on macOS (Apple Silicon)
• Linux via BlueZ should work through the standard bleak backend but is unverified
• Compatibility with Windows is unknown

Troubleshooting

On Raspberry Pi (and possibly other Linux machines using BlueZ), if you encounter a org.bluez.Error.InProgress error, try the following in bluetoothctl:

power off
power on
scan on

(See home-assistant/core#76186 (comment) for context.)

Support the project

If you find this unofficial project helpful, consider buying me a coffee! Your support helps maintain and improve this library.

License

This project is licensed under the MIT License - see the LICENSE file for details.