Mittzon Standing Desk → Home Assistant via ESPHome

Control an IKEA Mittzon standing desk from Home Assistant using an ESP32 wired directly to the handset panel's button contacts.

What works

• UP / DOWN control from Home Assistant switches
• Memory preset buttons (M1, M2) via HA button entities
• Go-to-position — set target height in cm via HA slider, ESP drives the desk there with predictive stop (+/-2mm precision after tuning)
• Live height tracking (cm + raw encoder ticks) via LIN bus RX monitoring
• Movement state sensor (idle / up / down)
• End-stop protection — soft limits prevent driving past safe range
• Physical button safety — if someone presses DOWN past the limit on the panel, ESP fires UP to trigger the controller's "two buttons = STOP" behavior
• Deadman timer — 30s max hold, auto-release

What doesn't work (yet)

• Full LIN bus control — the checksum turned out to be standard LIN enhanced (solved), but native control is still blocked by the open-collector physical layer and an unmapped command channel (see PROTOCOL.md)
• Panel LED status reading

Quick start

1. Open your Mittzon handset panel and solder 4 wires to the button pads (UP, DOWN, M1, M2) + GND
2. Connect to ESP32 GPIOs in open-drain mode (see HARDWARE.md)
3. Tap LIN bus (RJ45 pin 3) directly to GPIO16
4. Copy esphome/qbus-desk.yaml to your ESPHome config directory
5. Copy esphome/secrets.yaml.example to esphome/secrets.yaml and fill in your WiFi credentials, API key, and OTA/AP passwords
6. Flash and add to Home Assistant

See HARDWARE.md for full wiring details and panel teardown instructions.

Tuning inertia compensation

The go-to-position feature releases the drive button slightly before the target to let the desk coast to a stop via motor inertia. The Desk Inertia Compensation slider (0-300 ticks, default 100) controls how early the release happens.

• If the desk consistently overshoots the target: increase the value
• If it undershoots: decrease it
• The sweet spot depends on your desk's load and friction — start at 100 and adjust in steps of 10-20

No reflash needed — the slider is a runtime HA entity.

Hardware

• ESP32 WROOM-32 DevKit
• Thin silicone wires (AWG28-30)
• Powered directly from ROL desk controller 5V rail

Total cost beyond the desk: ~$3 if you have an ESP32 lying around.

Wiring overview

[ROL Group Controller]
       |
       | RJ45 cable (LIN bus + power)
       |
[Mittzon Handset Panel]
   |   |   |   |   |
  UP  DOWN M1  M2  GND
   |   |   |   |   |
   |   |   |   |   +-----+
   |   |   |   |         |
   |   |   |   +---+     |
   |   |   |       |     |
   |   |   +---+   |     |
   |   |       |   |     |
   |   +---+   |   |     |
   |       |   |   |     |
[GPIO26] [27] [33] [32] [GND]   <-- ESP32 WROOM-32
                                    (open-drain mode)

LIN bus tap (separate connection):
RJ45 pin 3 ----------- GPIO16 (UART2 RX)
RJ45 pin 8 ----------- ESP GND (shared with panel GND)

Power (from ROL desk controller):
RJ45 5V   ------------ ESP32 VIN (5V)
RJ45 GND  ------------ ESP32 GND

Home Assistant entities

Entity	Type	Description
Desk Up	Switch	Hold to raise, release to stop
Desk Down	Switch	Hold to lower, release to stop
Desk M1	Button	Momentary press for memory 1
Desk M2	Button	Momentary press for memory 2
Desk Target Height	Number / Slider	Set target height in cm (69-125), ESP drives to position
Desk Inertia Compensation	Number / Slider	Tune predictive stop distance (0-300 ticks, default 100)
Desk Height	Sensor	Current height in cm
Desk Position	Sensor	Raw encoder ticks
Desk Movement	Text Sensor	idle / up / down
Desk At Top	Binary Sensor	At upper end-stop
Desk At Soft Bottom	Binary Sensor	At lower soft limit
Desk Targeting	Binary Sensor	True while driving toward target
Desk Stop Targeting	Button	Abort current go-to-position

The journey

This wasn't the first approach. The full story — including LIN bus reverse engineering, a hardware MITM bridge, and why injection on an open-collector bus is mathematically impossible — is in JOURNEY.md.

The protocol findings (decoded PIDs, frame formats, what remains unsolved) are in PROTOCOL.md.

Project structure

├── README.md          # This file
├── HARDWARE.md        # Wiring, components, panel teardown
├── PROTOCOL.md        # iDrive/LIN bus findings
├── JOURNEY.md         # Full story including failed attempts
├── esphome/
│   └── qbus-desk.yaml # Final working ESPHome config
├── scripts/
│   ├── sigrok-decode.py # LIN frame decoder for sigrok captures
│   └── lin-analyze.py   # Per-second PID rate analysis
└── LICENSE            # MIT

Suggested topics

homeassistant esphome esp32 ikea-mittzon standing-desk lin-bus reverse-engineering smart-home home-automation

License

MIT