Height-Adjustable Desk with an ESP32 Controller

Problem

A standing desk only helps if you actually raise it, and I never remembered to press the button. What I wanted was for the desk to handle the routine itself: change posture on a schedule, without me, and without ever driving into something (or someone) in the way.

There is a second part to this. A desk that runs the routine also knows how long I stood and whether a focus block finished or got cut short, and that information is lost unless the desk sends it somewhere.

Solution

An ESP32-based controller wired between the desk’s original keypad and its motor controller:

• The desk’s control lines are intercepted through PC817 optocouplers rather than replacing the controller, so height changes can be driven in software while the original keypad keeps working exactly as it did. Nothing about the desk depends on my firmware being up.
• Two modes run on the same interrupt-driven state machine: an ergonomic mode that alternates sitting and standing on a fixed cadence, and a Pomodoro mode that ties the height change to the start and end of a 25-minute focus block. There are no delay() calls anywhere, so sensor polling, motion control and the schedule share a single core without blocking each other.
• An array of three VL53L0X Time-of-Flight sensors is read before any movement starts, and the manoeuvre aborts if the path is blocked. The check runs ahead of every state transition instead of reacting once the desk is already moving.
• Completed blocks are published over MQTT to a time-series database on a NAS, which is what lets a second application read them.

Where it stands

The hardware design is settled: components chosen, optocoupler interface to the keypad worked out, sensor array positioned, and the MQTT topic layout and database schema defined. The firmware is the part still being written, starting with the state machine and the safety layer.

I’m publishing it at this stage on purpose. Most of the decisions in a project like this are made before the code compiles: whether to replace the controller or sit beside it, whether safety is checked before or during motion, and what counts as a “block” once it has to survive a reboot.