Autonomous Standup Desk Controller

This writeup is still WIP

The Idea

I bought a standing desk from Autonomous (Smart Desk 2 Home Office). After setting it up, I was wondering how the controller and the table/motor controller communicate with each other.

ToDo

• More detailed writeup
• Finish implementing protocol on ESP32 (possibly with wifi control, "full system" in the future?)

Already done

• Written overview of the protocol
• Implement most of the needed commands
  • controller can move the desk up, down, go to preset, and get current height

First impressions

Opening up the controller reveals nicely labeled PINs.

Thus we now only know that UART is used to transfer data, but also which wire carries which signal:

color	function
red	sleep(?)
orange	GND
green	TX
yellow	RX
blue	5V

After some trying out, I found the baudrate: 9600

Height-Profiles are not saved on this controller - they are stored in the desk.

The controller board uses a STC12C5612AD uC. It features:

• 3,5-5,5V
• 8 Bit
• 23 I/O pins
• 1x UART
• 768 Bytes RAM
• 4K-30 KB program memory size (according to datasheet)

Datasheet

My Setup

I used a DSView Logic Analyzer which I bought here from Banggood.

I did not dismantle the controller that shipped with my desk. Instead, I asked the customer support for a spare one / replacement. They shipped it to me for 27€.

I opened up the casing (standard screws) and found a nicely labeled PCB where I could attach the probes to. Later I desoldered the board from the cable so I could connect my ESP32 with the cable.

I never tried running the ESP32 in parallel to the original controller. There might be interference since the used communication setup is not a bus system and not designed for multiple masters/slaves.

You can find my captured data from the logic analyzer in the folder "logic_analyzer".

Using my controller implementation

If you are only interested in reading about the protocol, skip this part and scroll down.

This is not an Arduino library. This is C++ based on the ESP IDF.

The general setup is easy. You need to include these two header files:

#include "hw_interface/uart_device.h"
#include "app/autonomous_controller.h"

Now you can prepare the controller:

//create an object that handles the uart connection
//we use UART_NUM_2 and the pins 23 + 22
uart_device uart(UART_NUM_2, 9600, 23, 22);

//create an autonomous controller (it needs the uart handler)
//if the uart is configured differently, the construcor
//will automatically set baudrate, data and stop bits
autonomous_controller controller(&uart);

You are all good to go. Now you can move your desk up and down (provided you have all the wires hooked up correctly). Some examples:

#move the desk to the height value 0x4D
#note: I might add a conversion in the future so you can
#use logical units such as cm
controller.go_to_height(0x4D);

#the same as when you press the button "1"
#	->move to the saved preset height
controller.go_to_preset(controller.button_1);

#pretend you are pressing buttons 1 and 2 simultaniously
#I don't know why you might want to do that...
controller.send_button(controller.button_1 | controller.button_2);

#move the table down 1 step
#you can use both commands - they do the same
controller.go_down();
controller.send_button(controller.button_down);

#...
#please have a look at the file autonomous_controller.h for more details

Protocol

Received Data

When no button is pressed, we keep receiving (repeating):

Base Message:

Byte 0	Byte 1	Byte 2	Byte 3	Byte 4	Byte 5
0x98	0x98	0x00	0x00	(height)	(height)
0x98	0x98	0x03	0x03	(height)	(height)

Height can be a value between 0x4B and 0x7B

I am not really sure about the meaning of 0x03 as byte 2+3. I have mostly seen 0x00, but sometimes also 0x03.

Height indication:

Height: 29.5

Last 2 Bytes of Message: 0x4B, 0x4B

Height: 29.9

Last 2 Bytes of Message: 0x4C, 0x4C

Height: 30.3

Last 2 Bytes of Message: 0x4D, 0x4D

Height keeps increasing in steps of 0.4 Message keeps increasing by 1 ...

Height: 48.0

Last 2 Bytes of Message: 0x7A, 0x7A

Height: 48.4

Last 2 Bytes of Message: 0x7B, 0x7B

Transmitted Data

Base message:

Byte 0	Byte 1	Byte 2	Byte 3	Byte 4
0xD8	0xD8	0x66	(button)	(button)

Button values:

⬇️ 0x01 (0b0000_0001)

⬆️ 0x02 (0b0000_0010)

1️⃣ 0x04 (0b0000_0100)

2️⃣ 0x08 (0b0000_1000)

3️⃣ 0x10 (0b0001_0000)

4️⃣ 0x20 (0b0010_0000)

Ⓜ️ 0x40 (0b0100_0000)

Pressing up

0xD8, 0xD8, 0x66, 0x00, 0x00

0xD8, 0xD8, 0x66, 0x02, 0x02

(keep going with end 0x02 as long as the button is pressed)

Pressing Down

0xD8, 0xD8, 0x66, 0x00, 0x00

0xD8, 0xD8, 0x66, 0x01, 0x01

(keep going with end 0x01 as long as the button is pressed)

Pressing 1

0xD8, 0xD8, 0x66, 0x00, 0x00

0xD8, 0xD8, 0x66, 0x04, 0x04

(keep going with end 0x04 as long as the button is pressed)

Pressing 2

0xD8, 0xD8, 0x66, 0x00, 0x00

0xD8, 0xD8, 0x66, 0x08, 0x08

(keep going with end 0x08 as long as the button is pressed)

Pressing 3

0xD8, 0xD8, 0x66, 0x00, 0x00

0xD8, 0xD8, 0x66, 0x10, 0x10

(keep going with end 0x10 as long as the button is pressed)

Pressing 4

0xD8, 0xD8, 0x66, 0x00, 0x00

0xD8, 0xD8, 0x66, 0x20, 0x20

(keep going with end 0x20 as long as the button is pressed)

Pressing M

0xD8, 0xD8, 0x66, 0x00, 0x00

0xD8, 0xD8, 0x66, 0x40, 0x40

(keep going with end 0x40 as long as the button is pressed)

Analyzing the protocol

• Controller->Desk: Every message contains 5 bytes

• Controller->Desk: Message always starts with 0xD8, 0xD8, 0x66

• Controller->Desk: First and last 2 bytes always repeat

• Desk->Controller: Every message contains 6 bytes

• Desk->Controller: Message always starts with 0x98, 0x98, 0x00, 0x00

• Desk->Controller: all bytes repeat (1st byte = 2nd byte, 3rd = 4th, 5th = 6th)

• Every button corresponds to 1 bit in the message

  • 7 buttons, 8 bit -> highest bit unused (?)

• The controller sends the current state of the buttons after receiving a message from the desk

• The motor controller seems to only move the desk as long as it is receiving data (0x00 as button-data seems to be enough)

• Messages are sent every ~50ms