QN Scales

The QN protocol runs on many Renpho, Arboleaf, FITINDEX, GE and Sencor scales and their rebadges. Most work without any option; the ble.qn_* options adjust the handshake for firmware that expects it differently.

Supported Models

• Renpho ES-CS20M, ES-32MD, Elis 1, and FITINDEX and Sencor rebadges.
• Arboleaf scales with eight electrodes (19-byte dialect).
• GE CS 10 G ("Fit Plus") and rebadges (20-byte extended dialect).

Some ES-CS20M and Elis 1 units never accept a connection. ble-scale-sync then reads the weight from their broadcast, and body composition is estimated from BMI, because the broadcast carries no impedance. ble-scale-sync diagnose <MAC> (npm run diagnose -- <MAC> from a clone) shows whether a unit is connectable. Newer ES-CS20M revisions on service 0x1A10 use Renpho's own protocol instead, see Renpho Scales.

The firmware variants differ by the length of the scale-info frame the scale sends after connecting. With runtime.debug: true the log names it:

QN: scale info (19B, dialect=es26m), factor=100, proto=0xff

This page names the dialects by that length: 18B and 19B are the 18- and 19-byte dialects, 20B and longer the extended dialect, anything else the classic dialect. The dialect= value is an internal name.

If the scale-info frame gets lost, which can happen on a proxy transport, the log shows this line instead:

QN: fallback: no 0x12 received, running handshake with proto=0xff

Its proto value is the byte ble-scale-sync used (qn_protocol_byte, or 255), not one the scale sent.

Setup

1. Set ble.scale_mac to the scale's address (scan lists it).
2. Make the first user in config.yaml the first user in the vendor app, with the same birth_date, height, gender and is_athlete. Several options below send that user's profile to the scale.
3. Set that user's last_known_weight, or a weight_range narrow enough that its middle is close to their weight. The scale is sent that number as a weight anchor before the weigh-in.
4. Weigh in and stay on the scale until its display shows the results.

A weigh-in that worked logs Measurement: with the weight and impedance.

Options

Try these in order when the scale connects and completes the handshake, but no weight arrives. Change one thing per weigh-in and keep each option that helped. An unset option changes nothing.

1. qn_protocol_byte: the protocol byte the handshake echoes back, 0 to 255. Try 0, then 255, then the proto value from the QN: scale info line if your log has one. A wrong byte gives no error, only silence.
2. qn_user_key: 18- and 19-byte dialects only. Set 1000, the key the Feelfit, Arboleaf and GE apps use, when the debug log shows QN: the scale did not accept the profile for user slot 1 (#331) and the display shows only the weight. The profile frame then carries this key and the first user's profile.
3. qn_weight_ack: true: sends the weight anchor right after the start command and acknowledges each live weight frame with its own weight, as the vendor apps do. On the 19-byte dialect it also sends the first user's age, height and sex. On by default on the extended dialect; false turns it off there.
4. qn_time_sync_long: true, keeping qn_weight_ack on: sends the 9-byte clock frame with the host's UTC offset. In Docker set TZ, or the offset sent is UTC.
5. qn_config_long: true, keeping both above: sends the 10-byte config frame the vendor app sends.
6. qn_a4_prelude: true, last: sends two extra frames the vendor app sends. They overwrite data the scale keeps for its first user, and a session that sends them never uses the scale's own body composition.

ble:
  scale_mac: 'AA:BB:CC:DD:EE:FF'
  qn_weight_ack: true
  qn_time_sync_long: true

All options apply on the next weigh-in without a restart. If one of them makes your scale report, say which one on #331, with the QN: scale info line.

Options with Side Effects

• qn_report_byte sends, on every connection, a frame that deletes the user slots its bits select on the scale (252 deletes slots 3 to 8), with any weigh-ins stored for them. Leave it unset unless a scale that reported weights stopped after you updated ble-scale-sync, and nobody else uses the scale.
• qn_result_ack: true (Experimental, 19-byte dialect) sends the end-of-measurement frame of the vendor's published SDK after the last result frame. Report results on #331.

Arboleaf Scales (19-Byte Dialect)

Set qn_weight_ack: true and qn_time_sync_long: true from the start and keep qn_a4_prelude off.

The scale measures body composition for about 14 seconds after the weight settles, so the connection stays open until its last result frame. If that frame never comes, the weight goes out alone after at most 40 seconds.

The scale computes body fat, water, muscle, bone, visceral fat, BMR and body age for the profile it was sent. These are exported, with body age as metabolic age, when both hold:

• the weigh-in is matched to a user with exactly the age, height and sex of that profile;
• the scale measured after it accepted the profile.

The log then says QN: using the scale's own body composition for this weigh-in (#331). Otherwise it names the reason and the weigh-in gets the BMI estimate. With several users only the first user can get the scale's values. The scale has no athlete mode.

Weigh-ins the scale stored while nothing was connected arrive on the next connection and go, with their own time and weight only, to the exporters that can record a past measurement.

GE CS 10 G and Extended-Dialect Scales

The scale waits for a weight anchor close to the weight of the person on it. The anchor is the first user's last_known_weight, or the middle of their weight_range when that range lies between 20 and 250 kg and spans no more than 100 kg. Without either, the log warns QN: no usable weight anchor in config and a fixed value is sent. Once the scale streams, every frame is acknowledged with its own weight, so the anchor matters only for the start.

Stored Weigh-Ins on the 18-Byte Dialect

With qn_user_key set and the profile accepted, the app also asks an 18-byte scale for the weigh-ins it stored while nothing was connected. Those of user slot 1, or of no user, go out once with their own time to the exporters that can record a past measurement. Without the option such a weigh-in is not exported, and the normal log gives its weight and time so you can add it by hand.

A stored weigh-in is exported once: the newest exported one is recorded in .scale-dedup-marks.json next to config.yaml.

Troubleshooting

The scale connects, the handshake completes, no weight arrives

Work through Options in order. Make sure someone stands on the scale during the connection, since a scale nobody stands on looks the same. If none of the options helps, open an issue with a log taken with runtime.debug: true during one weigh-in, the scale model, the transport and the options you tried.

The display shows only the weight

The scale refused the profile frame. Set qn_user_key: 1000 (18- and 19-byte dialects). If the normal log then says QN: the scale refused the profile frame sent with ble.qn_user_key 1000, the vendor app set up slot 1 with another key or never set it up; check that the first user in config.yaml is the first user in the vendor app.

The scale works for one person in the house only

On the extended dialect the anchor comes from the first user. Set last_known_weight for that user, or narrow weight_range so its middle is close to them, as in GE CS 10 G and extended-dialect scales.

Body fat differs between weigh-ins on an Arboleaf

A weigh-in without measured body composition, with dry feet for example, gets the BMI estimate instead of the scale's values. estimate_body_composition: false for the user exports none instead, see Configuration.