Open-Source eInk Bike Computer: DIY bike computer on e-ink display with ANT protocol support

What it does

OpenTrailPaper is open-source firmware that turns a LilyGO T5S3 e-paper display board into a bike computer. The device records GPS tracks, stores offline maps, follows GPX routes, and logs rides in FIT format. It pairs with Bluetooth sensors to capture heart rate, power, and cadence data. Rides can be reviewed later via a companion iOS or Android app. The device operates fully offline after maps and routes are loaded—no phone or internet required during a ride.

Who it is for

Cyclists interested in building their own bike computer rather than buying a finished product. The project appeals to makers and tinkerers comfortable assembling hardware and loading firmware. There is no subscription or account required, so it suits riders who value data ownership and local storage. Users need to source the LilyGO board themselves and handle the assembly and weatherproofing.

Pricing

The site does not show prices.

How it stands out

The e-paper display offers excellent readability in direct sunlight with minimal battery drain compared to LCD screens. The device requires only a single inexpensive microcontroller board and runs entirely open-source, with firmware flashable from a web browser. ANT protocol support is implemented via custom ESP32 register work. No vendor lock-in, no mandatory cloud syncing, and no subscription fees distinguish it from commercial bike computers. Offline maps, routes, and ride storage all work locally on the device.

What a founder should check

First, evaluate switching costs from incumbents like Garmin and Wahoo. Commercial units offer refined hardware (better GPS, barometers, build quality) and ecosystem polish that this DIY approach currently lacks. Second, confirm the market size: how many cyclists actually prefer building their own computer over buying a finished device, and what willingness-to-pay exists for a kit or pre-assembled option. Third, assess the moat. The open-source nature means competitors can fork the firmware easily, and the underlying hardware is commodity. Revenue opportunities (selling kits, premium apps, or subscriptions) would face uphill adoption battles against free, self-hosted alternatives.

Thinking of building something like this?

Every launch here is a competitor to somebody's idea. If yours is close, check it against the market before you build: the Full Check names the rivals, the prices and the gaps.