--- service: "Publicasta" schema_version: "1.0" article_id: 530 title: "OpenTrailPaper turns a LilyGO e-paper board into an open bike computer" language: "en" default_language: "en" canonical_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=en" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=en" api_url: "https://publicasta.com/api/public/v1/channels/open_source_radar/articles/opentrailpaper_open_epaper_bike_computer?lang=en" channel_url: "https://publicasta.com/api/public/v1/channels/open_source_radar" channel_articles: "https://publicasta.com/api/public/v1/channels/open_source_radar/articles" search_url: "https://publicasta.com/api/public/v1/search" documentation_url: "https://publicasta.com/api-docs#reading-publicasta" openapi_url: "https://publicasta.com/api-docs/openapi.json" published_at: "2026-09-07T07:30:59+00:00" updated_at: "2026-09-07T07:30:59+00:00" translations: - language: "ar" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=ar" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=ar" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=ar" - language: "de" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=de" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=de" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=de" - language: "en" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=en" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=en" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=en" - language: "es" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=es" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=es" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=es" - language: "fr" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=fr" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=fr" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=fr" - language: "pl" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=pl" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=pl" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=pl" - language: "ru" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=ru" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=ru" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=ru" - language: "zh" html_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer?lang=zh" markdown_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.md?lang=zh" json_url: "https://publicasta.com/open_source_radar/opentrailpaper_open_epaper_bike_computer.json?lang=zh" --- # OpenTrailPaper turns a LilyGO e-paper board into an open bike computer > A young Apache-2.0 project combines offline maps, GPX navigation, FIT recording and BLE sensors on one e-paper board. It is ready for careful experimentation, not blind reliance. ![An exposed LilyGO T5S3 e-paper development board mounted on bicycle handlebars, showing a simple monochrome offline map and ride data beside a microSD card and USB-C cable](https://publicasta.com/storage/projects/10/pages/530/2026/09/29a7c9b7-041d-4ee2-bc28-0dfe2505eedf.webp) ## An open bike computer you can inspect, alter and repair OpenTrailPaper is a young open-source bicycle-computer project built around the LilyGO T5S3 4.7-inch E-Paper PRO board. It brings together GPS navigation, an e-paper display, offline maps, GPX routes, ride recording and Bluetooth Low Energy sensors in a device whose firmware can be examined and changed. The repository uses the Apache License 2.0 for the main project, while its NOTICE file preserves the separate terms that apply to third-party components and OpenStreetMap-derived data. That combination makes it an intriguing workshop project, not a ready-made substitute for a commercial head unit. OpenTrailPaper’s own site describes it as a development project rather than a finished, weatherproof product. Anyone who installs it on a bicycle must still solve the physical problems: a secure mount, protection from rain, resistance to vibration and a practical enclosure. Reliability, positioning performance and display behaviour on long rides also need to be established on real hardware. The distinction matters because the software already covers a useful core. According to the project documentation, the head unit can display preloaded offline maps, follow a GPX route and write a 1 Hz FIT activity file to an SD card. It can pair with BLE heart-rate, power, speed and cadence sensors. Once maps and routes have been prepared and transferred, navigation and recording do not require a phone during the ride. These are documented capabilities, not results independently reproduced for this review. Compatibility with every sensor and FIT-processing service should not be assumed, nor should flawless recovery from a depleted battery, lost satellite fix or interrupted file write. “Phone-free” also describes the ride itself, not the whole workflow: maps, routes, settings and firmware must first be prepared elsewhere. ## One board, with an important name to check At present, the project identifies only the LilyGO T5S3 4.7-inch E-Paper PRO as supported. LilyGO specifies an ESP32-S3, 16 MB of flash, 8 MB of PSRAM and a 960 × 540 e-paper panel, along with GPS, an SX1262 LoRa radio, GT911 touch controller, real-time clock and 1500 mAh battery. This is a capable collection of parts for a compact experimental head unit, and using a single integrated board lowers the barrier compared with wiring each subsystem separately. Buyers must pay close attention to the “PRO” suffix. LilyGO’s Lite variant omits GPS and LoRa, so it is not an equivalent purchase for this build. The project expresses an interest in ports to other hardware, but that should not be read as current plug-and-play support. A different display size would also require interface work rather than a simple board definition change. E-paper is central to the project’s appeal. A 4.7-inch monochrome panel can keep map and ride information legible without behaving like a bright miniature phone. It also imposes its own design constraints: refresh handling, rapidly changing data fields and map interaction have to be judged on the actual device. The specification alone cannot show whether the chosen update strategy feels comfortable at speed or under changing route conditions. The reference board also lacks a pressure sensor. OpenTrailPaper therefore derives elevation and climbing information from elevation grids embedded in downloaded map tiles. That can provide useful terrain context, but it is fundamentally different from barometric measurement. There is no elevation estimate where the relevant tiles are missing, and short local rises may escape the resolution of the terrain data. Claims about total-ascent accuracy would require comparison with a reliable reference over representative rides. ## The software path from desk to handlebars OpenTrailPaper provides companion applications for routes, maps, rides, settings and firmware transfer. The project links to an iOS App Store listing. On Android, version 0.3 appeared as a GitHub prerelease on September 7, 2026, with an APK for sideloading. That prerelease status is a useful warning: Android users are joining a beta path, not installing a settled Play Store release. The APK’s signing key also differs from the Play Store key, so it cannot update a copy installed from Google Play. There is a browser-based alternative for two important setup jobs. The project site offers USB firmware flashing through Web Serial and can generate offline maps in the browser. This route requires desktop Chrome, Edge or Opera; Safari, Firefox and mobile browsers are excluded. The flasher may require the board to be placed into the appropriate mode with its BOOT and RESET controls. The workflow was inspected but not exercised on hardware here, so it should be approached as a convenient installation option rather than a guarantee of effortless recovery. Browser-generated maps use OpenStreetMap data obtained through Overpass. Unlike maps prepared through the companion application, however, they do not include the elevation data used by the head unit for climbing calculations. The choice of preparation method consequently changes more than convenience. Riders who want elevation fields must make sure their map package contains the required grids, while anyone redistributing generated map data must also respect the applicable Open Database License and attribution requirements. This separation of duties is sensible for constrained hardware. Route selection, regional map processing and firmware management happen on a more capable phone or computer; the head unit receives the material needed for the ride. It also means that a prospective builder should test the entire round trip before relying on it: prepare a route, transfer the relevant tiles, pair sensors, record a representative activity and open the resulting FIT file in the intended service. ## Sensors, LoRa and carefully drawn boundaries Cycling sensors pair over Bluetooth Low Energy. The documentation names heart-rate, power, speed and cadence devices, but does not establish universal compatibility across every manufacturer or combined sensor profile. There is no basis for advertising ANT+ support. The project’s author linked a separate experimental ESP32 ANT implementation during the Show HN discussion, but that is not evidence that ANT+ is integrated into OpenTrailPaper. The PRO board’s SX1262 radio is used for a more unusual feature: documented Meshtastic messaging. OpenTrailPaper operates as a leaf node, which means it does not relay other users’ traffic and does not report its position. That limited role is easier to reconcile with a bicycle computer’s power and privacy concerns than running a full routing node would be. Even so, interoperability and radio range were not tested for this review; both will depend on configuration, antenna performance and local conditions. The boundaries are as informative as the feature list. The site lists no magnetometer, no pressure sensor and only basic GPS. It does not claim waterproofing. Those omissions prevent the project from being mistaken for a polished adventure-navigation appliance, but they also make the engineering choices legible. Instead of concealing compromises behind a sealed product, OpenTrailPaper gives builders a platform they can inspect and, if they have the skills, improve. Firmware v1.19, published as a regular release on September 4, addressed first-time sensor discovery on new or factory-reset devices. The release note says previously paired units were unaffected. That is a narrowly described fix to a practical onboarding problem, although it was not verified on a physical unit here. GitHub showed the downloadable asset as updated on September 7 with SHA-256 `d73059b915e795b89d27077c89bc4e07356f68b431878cec5629307e6526150e`. Because the asset changed after publication and releases can be edited, users should verify the current download rather than treating the original release date as proof of an immutable binary. ## Why this release is worth watching now OpenTrailPaper’s public repository was created on July 12, 2026, and GitHub recorded a push on September 7. The sequence of firmware v1.19 on September 4 and the Android 0.3 prerelease three days later shows a project moving quickly across both the head unit and its supporting tools. It is also attracting attention: the September 4 Show HN post had reached 409 points and 130 descendants when the research was checked, including 38 top-level comment IDs. Those numbers establish freshness and interest, not quality. Stars, discussion totals and repository activity do not reveal how many people are using the device, whether it survives bad weather, or whether a long recording remains intact. OpenTrailPaper is unusually timely for an open-source radar because there is already code, a downloadable firmware release, a browser flashing workflow and an installable Android beta to examine. Even so, the evidence supports an invitation to experiment rather than a buying recommendation. What makes the project significant is not an attempt to reproduce every feature of a Garmin or Wahoo. It offers a comparatively understandable base for riders who care about offline operation, accessible ride files and the ability to inspect the software controlling their navigation device. GPX input, FIT output, local maps and standard BLE sensor categories form a practical core. The open design also creates room for contributors to investigate display layouts, file handling, sensor support and ports without waiting for a manufacturer’s product roadmap. That freedom comes with several licensing layers. The main project is under Apache License 2.0, but that label does not automatically cover every component or generated map. The repository’s NOTICE identifies separate terms for third-party software, while maps derived from OpenStreetMap remain governed by ODbL obligations. Anyone merely building a private unit has a simpler task than someone packaging firmware, dependencies and regional maps for redistribution; the latter should review each relevant notice and attribution requirement rather than relying on the repository’s headline licence. ## A sensible first field test A prospective builder should begin with the exact PRO board and treat the first installation as a bench exercise. Confirm that firmware can be flashed and recovered, load a small familiar region, transfer a short GPX route and check that the map remains available with the phone disconnected. Pair each intended BLE sensor individually, then together, and verify that the displayed values are plausible. After a short ride, inspect the FIT file in the service that will actually be used and check timestamps, track continuity and sensor fields. The next test should target failure rather than features. Restart the unit midway through a practice route, temporarily deprive it of a satellite view, and confirm what happens when maps or elevation grids do not cover the surrounding area. Check screen readability and refresh behaviour in the conditions in which the bicycle is normally ridden. Only then is it useful to measure endurance with the chosen display settings, sensors and radio use. The project site reports roughly 7.4 hours from one maintainer test with the 1500 mAh battery. That is a useful planning datum, but not a guaranteed runtime for every assembly or pattern of use. A rider considering an all-day trip should measure the completed unit rather than extrapolating from that single result. Physical preparation is equally important. The board is not sold here as a sealed bicycle computer, so a field build needs a secure mount and deliberate protection from water and vibration. These are part of the project, not cosmetic work to postpone until after the software is trusted. ## Who should try it—and who should wait OpenTrailPaper is best suited to developers, electronics hobbyists and technically confident cyclists who already own, or deliberately want to explore, the specified LilyGO board. It offers enough documented functionality to support meaningful experiments rather than a screen-only demonstration. Its offline model is particularly appealing for riders who want a dedicated device on the handlebars while retaining control over routes and recorded files. It is not yet the prudent choice for someone who needs a weatherproof appliance, guaranteed sensor compatibility, verified ascent figures or dependable navigation on an important unsupported ride. Users dependent on ANT+ should also wait unless the project itself gains that integration; the existence of a separate experiment does not fill the gap. Likewise, buyers of the Lite board or another display should expect development work, not an alternative installation path. The right verdict is therefore narrower, and more useful, than calling it an open-source replacement for an established commercial computer. OpenTrailPaper is a young, actively changing foundation with firmware, offline-map tools and the documented functions needed for a controlled test ride. Its value lies in exposing the whole path from route preparation to on-bike recording—and in making the remaining limitations impossible to ignore. For builders prepared to validate each step and protect the hardware, it is worth trying now. Everyone else should watch the releases and field reports as the project earns evidence beyond its documentation.