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ESP32 Bike Computer

I’ve been tinkering with an ESP32 that comes with a built-in 1.47-inch display, and I thought—why not turn it into a bike computer? The idea is simple: use the ESP32 as a BLE device that pairs with my phone via Web BLE and also communicates with my Garmin watch. With a bit of work, I managed to display my current speed, heart rate, time, and live weather updates. Here’s what I did;

The Setup

The UI is designed using SquareLine Studio, which generates LVGL code for the ESP32 display. This allows for nice interactive interface with minimal effort.

The ESP32 acts as a BLE peripheral, listening to data from the phone which acts as a hub, relaying data to the ESP32 via Web BLE. The Garmin watch also connects to the same web page using BLE, sharing heart rate data.

first iteration of ui Current ui showing speed, heart rate time and weather

The Good Stuff

Everything runs directly in the browser using Web BLE thanks to project fugu!. No bulky hardware, just a little ESP32 module on the bike powered by a small powerbank.

The Challenges

There are a few challenges to tackle. One of the biggest drawbacks is the screen limitations—the built-in display is too small and not bright enough, making it difficult to read in sunlight. I’m considering switching to a different ESP32 form factor with an e-ink or brighter AMOLED display. Another issue is the Web Geolocation limitation; since the phone has to stay active, geolocation data stops updating if the browser tab is inactive.because of this power consumption is a concern, as keeping the phone active drains the battery.

This has been a fun little experiment, and while it’s not a perfect solution yet, there’s definitely room for improvement—like finding a way to keep geolocation running in the background—but for now, it’s a cool, lightweight bike computer that does the job.

TODO feature list