No sensor values for S400 scales

[pricei]

Describe the Bug / 描述问题

I'm using a set of Xiaomi S400 scales that connect to a Xiaomi Smart Home Hub 2. Both devices were setup using the Android Xiaomi Home app and work correctly. The weight and body fat percentage (BFP) measurements for a user are correctly recorded in the app each time they use the scales.

I then installed the ha_xiaomi_home integration to access the S400 scales data for a home automation project. The integration successfully identified the hub and scales. The sensor and controls data for the hub is correct. However, no sensor values appear for the scales and all Notifiers and Events are shown as Unknown (see screenshot 1) except for a customised service event.

I have noticed that each time the scales are used, two Customized Event-1 events are triggered in Home Assistant. Each event includes three customised arguments (see screenshots 2 and 3):
Customized argument 5: This appears to identify the user using the scales.
Customised argument 3: This appears to be a Unix timestamp when the weighing occurred.
Customised argument 4: I'm guessing this may be the weight or BFP value of the user? However, I can't work out how the value has been encoded.

I'm assuming I should be able to access the data collected by the S400 scales in Home Assistant as sensor values? As a workaround, if the value of Customised argument 4 in each weighing event is a user's weight or BFP value, I can probably process this data and generate sensor values using a Home Assistant automation. Can anybody confirm what this event argument actually represents and how it is encoded?

How to Reproduce / 复现步骤

Setup S400 scales and Hub 2 using Xaomi Home phone app.
Create Xiaomi cloud account using phone app.
Install ha_xiaomi_home integration
Generate measurements using scales.

Expected Behavior / 预期结果

Each user's weight, body fat % (and possibly heart rate) should appear as sensor values.

Reproduce Time / 问题复现的时间点

2026-01-22 11:00:00

Home Assistant Logs / 系统日志

Thefollowing log entries are written to HA syslog by an automation triggered when the following event occurs: event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022

Scales event data: {'id': '0', 'idx': '0', 'alias': None, 'platform': 'state', 'entity_id': 'event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022',
'from_state': <state event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022=2026-01-24T08:47:26.923+00:00; event_types=['Customized Event-1'], event_type=Customized Event-1, Customized Argument 5=4, Customized Argument 4=1435238400, Customized Argument 3=1769244449, friendly_name=Xiaomi Scale S400 Customized Service For Ble Customized Event-1 @ 2026-01-24T12:01:51.167942+00:00>,
'to_state': <state event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022=2026-01-25T07:49:34.709+00:00; event_types=['Customized Event-1'], event_type=Customized Event-1, Customized Argument 5=3, Customized Argument 4=1209035391, Customized Argument 3=1769327375, friendly_name=Xiaomi Scale S400 Customized Service For Ble Customized Event-1 @ 2026-01-25T07:49:34.709880+00:00>,
'for': None, 'attribute': None, 'description': 'state of event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022'}

Scales event data: {'id': '0', 'idx': '0', 'alias': None, 'platform': 'state', 'entity_id': 'event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022',
'from_state': <state event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022=2026-01-25T07:49:34.709+00:00; event_types=['Customized Event-1'], event_type=Customized Event-1, Customized Argument 5=3, Customized Argument 4=1209035391, Customized Argument 3=1769327375, friendly_name=Xiaomi Scale S400 Customized Service For Ble Customized Event-1 @ 2026-01-25T07:49:34.709880+00:00>,
'to_state': <state event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022=2026-01-25T07:49:35.737+00:00; event_types=['Customized Event-1'], event_type=Customized Event-1, Customized Argument 5=3, Customized Argument 4=1096024064, Customized Argument 3=1769327375, friendly_name=Xiaomi Scale S400 Customized Service For Ble Customized Event-1 @ 2026-01-25T07:49:35.738104+00:00>,
'for': None, 'attribute': None, 'description': 'state of event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022'}

Log Timezone / 日志时区

Europe/UK (GMT)

Home Assistant Core Version / Home Assistant Core 版本

2026.1.3

Home Assistant Operation System Version / Home Assistant Operation System 版本

17.0

Xiaomi Home Integration Version / 米家集成版本

0.4.7

Additional Context / 其他说明

No response

[SusanPhevos]

Same as #1615

[pricei]

In case it helps somebody else, the automation below illustrates how the weight and heart rate measurements of different users can be captured from Xiaomi S400 scales connected via a Smart Home Hub 2. All measurements update separate input_number entities in Home Assistant.
Note: This automation does not process either of the impedance readings generated by the S400 scales (but could be easily extended to include these).

After a user completes the measurement process, the ha_xiaomi_home integration generates two customised events. Each includes the same customised arguments:

• Argument 5 is an 8-bit integer value that identifies the user. I believe this starts at 1 for the first user and increments for each additional user.
• Argument 3 is a Unix time stamp of when the measurement occurred.
• Argument 4 comprises the measurement payload and includes the weight, heart rate and an impedance reading. These values are encoded into a 32-bit integer value as follows: (impedance * 10) << 18 + (heart_rate - 50) << 11 + (weight * 10)

This Github article discusses the encoding method in more detail.

The first event includes the user's weight, heart rate and their high-impedance reading. The second event includes their low-impedance reading only. As no weight or heart rate values are included in the second event, this fact can be used to distinguish the two events.
Note: I believe the two impedance readings can be used with other information - such as the user's weight, height, age, etc - to calculate metrics such as the user's BMI, etc, if required.

The automation is triggered when the state of event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022 changes and comprises the following steps:

• All of the event data is written to the system log. This is for testing/debugging purposes only.
• The heart rate is derived from argument 4 and tested for a non-zero value. This identifies whether the event is the first or second following a weighing activity. As this automation only processes each user's weight and heart rate measurements, no action is taken for the second event.
• The user's weight is calculated and is used to update one of two input_number entities (for user1 or user2). This logic could be simplified for a single user or extended for more users.
• The user's heart rate is calculated and is similarly used to update one of two input_number entities.

The template code below is included for illustrative purposes only and would benefit from more robust parsing of data and code optimisation.

description: "Records a user's weight and heart rate from the event data generated after they measure themself"
mode: single
triggers:
  - trigger: state
    entity_id:
      - event.yunmai_de_blt_4_1nqh4nfc1gc00_ms104_customized_event_1_e_11_1022
conditions: []
actions:
  - action: system_log.write
    metadata: {}
    data:
      level: warning
      message: "Scales event data: {{ trigger }}"
  - choose:
      - conditions:
          - condition: template
            value_template: >
              {% set arg = trigger.to_state.attributes['Customized Argument 4'] %}
              {% set binary = "{0:032b}".format(arg | int(0)) %}
              {% set heart = binary[14:21] %}
              {{ (heart | int(base = 2)) != 0 }} 
        sequence:
          - action: input_number.set_value
            metadata: {}
            target:
              entity_id: >
                {{ iif (trigger.to_state.attributes['Customized Argument 5'] == 1, 'input_number.xiaomi_s400_weight_user1', 
                'input_number.xiaomi_s400_weight_user2' ) }}  
            data:
              value: >
                {% set arg = trigger.to_state.attributes['Customized Argument 4'] %}
                {% set kgToPound = 0.22046226218 %}
                {% set binary = "{0:032b}".format(arg | int(0)) %}
                {% set weight = binary[21:] %}
                {{ (weight | int(base = 2) * kgToPound ) | round(1) }}
          - action: input_number.set_value
            metadata: {}
            target:
              entity_id: >
                {{ iif (trigger.to_state.attributes['Customized Argument 5'] == 1, 'input_number.xiaomi_s400_heartrate_user1',
                'input_number.xiaomi_s400_heartrate_user2' ) }}  
            data:
              value: >
                {% set arg = trigger.to_state.attributes['Customized Argument 4'] %}
                {% set heartRateOffset = 50 %}
                {% set binary = "{0:032b}".format(arg | int(0)) %}
                {% set heart = binary[14:21] %}
                {{ (heart | int(base = 2)) + heartRateOffset }}

[Flanz926]

xiaomi_home port of the S400 weight/HR/impedance decode

Credit: @PoiScript found the bit-packing formula and built a full converter in XiaomiGateway3#1388; @pricei ported it here for weight+HR. Below is the same formula filling in both impedance values, as a plain template: sensor config for anyone on the official xiaomi_home integration (no custom component needed).

value = (impedance * 10) << 18 | (heart_rate - 50) << 11 | (weight_kg * 10)

weight     = value & 0x7FF          # /10 for kg
heart_rate = (value >> 11) & 0x7F   # +50 for bpm; 127 = not measured
impedance  = value >> 18            # /10 for Ω

Two events fire per weigh-in: first has weight (+HR if enabled) + impedance-high, second has only impedance-low (weight/HR bits are 0) — use "weight non-zero?" to tell them apart. Per PoiScript's findings, HR/impedance can be missing entirely (e.g. shoes on), and body-fat/BMI/etc. are calculated server-side by Xiaomi's cloud, not reproducible locally (see bodymiscale for a local BIA estimate instead).

Confirmed working unchanged on yunmai.scales.ms104 (S400 EU, MJTZC01YM) via xiaomi_home.

- triggers:
    - trigger: state
      entity_id: event.YOUR_DEVICE_ms104_customized_event_1_e_11_1022
  conditions:
    - condition: template
      value_template: >-
        {{ trigger.to_state is not none
           and (trigger.to_state.attributes.get('Customized Argument 4') | int(0)) % 2048 > 0 }}
  sensor:
    - name: "Scale Weight"
      unique_id: scale_s400_weight
      unit_of_measurement: "kg"
      device_class: weight
      state_class: measurement
      state: >-
        {% set v = trigger.to_state.attributes.get('Customized Argument 4') | int(0) %}
        {{ ((v % 2048) / 10) | round(1) }}
      attributes:
        user_duid: "{{ trigger.to_state.attributes.get('Customized Argument 5') }}"
        measured_at: "{{ trigger.to_state.attributes.get('Customized Argument 3') | as_datetime }}"
        raw_value: "{{ trigger.to_state.attributes.get('Customized Argument 4') }}"
    - name: "Scale Heart Rate"
      unique_id: scale_s400_heart_rate
      unit_of_measurement: "bpm"
      state_class: measurement
      state: >-
        {% set v = trigger.to_state.attributes.get('Customized Argument 4') | int(0) %}
        {% set hr = (v // 2048) % 128 %}
        {{ (hr + 50) if 0 < hr < 127 else none }}
    - name: "Scale Impedance High"
      unique_id: scale_s400_impedance_high
      unit_of_measurement: "Ω"
      state_class: measurement
      state: >-
        {% set v = trigger.to_state.attributes.get('Customized Argument 4') | int(0) %}
        {{ ((v // 262144) / 10) | round(1) }}

# Second event of the same weigh-in: weight/HR bits are 0, only impedance_low is present
- triggers:
    - trigger: state
      entity_id: event.YOUR_DEVICE_ms104_customized_event_1_e_11_1022
  conditions:
    - condition: template
      value_template: >-
        {{ trigger.to_state is not none
           and (trigger.to_state.attributes.get('Customized Argument 4') | int(0)) % 2048 == 0
           and (trigger.to_state.attributes.get('Customized Argument 4') | int(0)) > 0 }}
  sensor:
    - name: "Scale Impedance Low"
      unique_id: scale_s400_impedance_low
      unit_of_measurement: "Ω"
      state_class: measurement
      state: >-
        {% set v = trigger.to_state.attributes.get('Customized Argument 4') | int(0) %}
        {{ ((v // 262144) / 10) | round(1) }}

Attribute name is Customized Argument 4 on English HA; localized installs show the translated MIoT spec name instead (e.g. German: 'Verbundfelder (Impedanzwert, Herzfrequenz, Körpergewicht)') — check your own entity in Developer Tools → States and adjust. Reference via template: !include template.yaml, validate, restart HA.