💡 Bekant

Bekant is a hardware and firmware modification for the IKEA Bekant desk, combining an ESP32 with the AVR-based Megadesk replacement controller.

It provides simple two-button control with height presets, smart-home integration through Home Assistant and MQTT, over-the-air firmware updates, and the ability to flash the Megadesk controller directly from the ESP32.

Features

• Simple, intuitive two-button controls for manual movement and height presets
• Home Assistant integration via MQTT
• OTA updates for the ESP32
• Remote flashing of the ATtiny841-based Megadesk controller through the ESP32
• RGB visual feedback and audible error indication

Hardware

• Megadesk replacement controller board
• ESP32 with support for 29-35 V DC input, depending on your desk’s power supply
• Logic level shifter for 5 V to 3.3 V communication

Warning

Do not connect the desk’s 29–35 V supply directly to the VIN pin of a typical ESP32 development board. Only use a board specifically designed for this input voltage, or use a suitable buck converter.

A Megadesk replacement controller is required for this mod. The ESP32 is used to control the Megadesk controller and provide smart-home features.

It is recommended to get an ESP32 board with support for up to 35 V DC input, depending on the desk’s power supply. These aren’t very common, but the Waveshare ESP32-C6-Zero-B is an excellent choice. Alternatively any ESP32 board can be used, but a buck converter is then required to step down the voltage from 35 V DC to 5 V DC.

For safe communication between the ESP32 and the Megadesk controller, a logic level shifter is required. The Megadesk controller operates at 5 V logic levels, while the ESP32 operates at 3.3 V logic levels. A logic level shifter ensures that the signals are properly translated between the two devices. These are commonly available and can be found as breakout boards in various forms from different manufacturers. Tested product families include the TXS0104E and TXS0108E.

The logic level shifter can be hidden inside the stock controller enclosure, only exposing the ESP32 partially sticking out of the enclosure on the back side next to the cable. This mounting position can be beneficial as it provides easy access to the ESP32 USB port while also allowing the ESP32’s RGB status LED to light up the underside of the desk, providing visual feedback on the desk’s status.

Installation

• Wire the ESP32 and logic level shifter to the Megadesk replacement controller.
• Configure secrets.h with pin assignments.
• Build and upload the ESP32 firmware.
• Flash the Megadesk firmware through the ESP32.
• Verify operation physically and optionally through Home Assistant.

Wiring

Pin	Function	Comment
SCK	SPI SCLK / UART TX	Required
MISO	SPI MISO / UART RX	Required
MOSI	SPI MOSI	Required
RST	AVR reset	Required
TPUP	Up button
TPDN	Down button
OE	Level shifter control
ADC	Supply voltage monitor

During normal operation the SCK and MISO pins are used for serial communication with the Megadesk controller. The RST pin is normally unused, but can be handy to reset the Megadesk controller if it becomes unresponsive. These three pins in combination with the MOSI pin are also used to flash the Megadesk controller through the ESP32. No special programming hardware is required, as the ESP32 can act as a programmer for the Megadesk controller.

The TPUP and TPDN pins can be connected to enable simulation of physical button presses on the Megadesk controller. There’s normally no need to connect these pins, as the ESP32 can control the desk height through the Megadesk controller via serial communication. This is mainly useful for debugging and testing, but also allows for some interesting custom use cases.

Connecting OE allows the ESP32 to electrically isolate itself from the Megadesk controller by disabling the level shifter. This is mainly useful for development and debugging.

The IKEA Bekant desk has a bad reputation for having a power supply prone to failure. The ADC pin can be connected to the 35 V DC input voltage via a voltage divider, allowing the ESP32 to monitor the input voltage and report it through Home Assistant. This can be useful for detecting power supply issues before they cause problems.

Megadesk pinout diagram

      ┌────────────────────┐
TPUP ─┼ TPUP   ┌───────────┼─ MISO
TPDN ─┼ TPDN   │   ┌───────┼─ SCK
      │        │   │    ┌──┼─ RST
      │      MISO SCK  RST │
      │        +5 MOSI GND │
      │        │   │    └──┼─ 0 V DC
      │  x  x  │   └───────┼─ MOSI
      │        └───────────┼─ +5 V DC
      │ RED+ GND LIN x x   │
      └──┼────┼───┼────────┘
         │    │   └────────── LIN
         │    └────────────── 0 V DC
         └─────────────────── +35 V DC

ESP32 pinout diagram

┌──────────────────────┐
│                  VIN ├─ +35 V DC
│                  3V3 ├─ +3.3 V DC
│                  GND ├─ 0 V DC
│                      │
│             UART/SPI ├─ SCK
│             UART/SPI ├─ MISO
│                  SPI ├─ MOSI
│                      │
│       Digital output ├─ RST
│       Digital output ├─ OE
│                      │
│ Digital input/output ├─ TPUP
│ Digital input/output ├─ TPDN
│                      │
│         Analog input ├─ ADC
└──────────────────────┘

Logic level shifter pinout diagram

   0 V DC ────────┬──────── 0 V DC
+3.3 V DC ────┐   │   ┌──── +5 V DC
           ┌──┴───┴───┴──┐
           │ VCC GND VCC │
      SCK ─┤ A1  ──►  B1 ├─ SCK
     MISO ─┤ A2  ◄──  B2 ├─ MISO
     MOSI ─┤ A3  ──►  B3 ├─ MOSI
      RST ─┤ A4  ──►  B4 ├─ RST
     TPUP ─┤ A5  ◄─►  B5 ├─ TPUP
     TPDN ─┤ A6  ◄─►  B6 ├─ TPDN
       OE ─┤ OE          │
           └─────────────┘

Cable pinout diagram

──────┐
  Red ┼─ +35 V DC
White ┼─ 0 V DC
 Blue ┼─ LIN
──────┘

Software

PlatformIO IDE is required. It provides integrations for a wide range of IDEs — use whichever editor you are most comfortable with.

Define pin assignments and credentials in secrets.h.

Make sure to upload the ESP32 firmware before flashing the Megadesk controller, as the ESP32 is used as a programmer for the Megadesk controller.

Status LED

ESP32 boards with a WS2812 RGB LED can take advantage of the status LED functionality.

• Red: An error has occurred, this can mean the desk has reached a limit, is unresponsive, or that a communication error has occurred.
• Green: Desk is moving in response to a physical button press
• Blue: The desk is moving autonomously to a preset height or in response to a command
• White: Idle
• The light will switch off after a short period of inactivity.

Home Assistant

Home Assistant with MQTT is recommended for the best experience, but the desk also works fully offline. When the ESP32 successfully connects to MQTT, the desk will be auto-discovered in Home Assistant.

Category	Name	Description	Requirement
Controls	Height	Move to a specific height of choice
Controls	Preset high	Move to the preset high height
Controls	Preset low	Move to the preset low height
Sensors	Desk	Current height of the desk
Sensors	Preset high	Preset high height
Sensors	Preset low	Preset low height
Configuration	Output enable	Control the logic level shifter’s OE pin	PIN_OE
Configuration	Preset high	Set the preset high height
Configuration	Preset low	Set the preset low height
Configuration	Reboot	Reboot the ESP32
Configuration	Reset	Hold the Megadesk controller in reset
Diagnostics	Button down	Simulate a physical button down press	PIN_TPDN
Diagnostics	Button up	Simulate a physical button up press	PIN_TPUP
Diagnostics	Calibrate	Recalibrate the leg encoder sensors
Diagnostics	Encoders	Encoder raw height in average
Diagnostics	Offset	Displays the current leg offset height
Diagnostics	Power supply	Input voltage of the desk’s power supply	PIN_ADC
Diagnostics	Serial RX	Last UART message received
Diagnostics	Serial TX	Last UART message sent
Diagnostics	Temperature	Internal temperature of the ESP32
Diagnostics	Wi-Fi signal	Wi-Fi RSSI signal strength of the ESP32

To avoid cluttering the Home Assistant interface, only a handful are enabled by default.