OpenTrailPaper - DIY e-paper bike computer
Show HN: Open-Source eInk Bike Computer
OpenTrailPaper is an open-source firmware that turns the LilyGO T5S3 4.7" E-Paper PRO into a fully functional bike computer. It displays ride data and offline maps, follows GPX routes, records FIT files, and connects to Bluetooth sensors. The device works independently once maps and routes are loaded, with no account or subscription required. An optional iOS companion app simplifies route planning, map building, and firmware updates. While it's a development project requiring DIY assembly and protection, it offers a customizable and affordable alternative to commercial bike computers.
OpenTrailPaper is a DIY e-paper bike computer that shows ride data and offline maps, follows GPX routes, records FIT files and connects to Bluetooth sensors.
- Rebelgecko
The semi-interactive walkthrough on the website is really cool, great way to show the UX.
I've always wanted to use a round display and an 18650 to plop a mini bike computer into my headset (replacing the cap). There was a Kickstarter years ago for a project doing that, but it seems to have fizzled out
- neoCrimeLabs
Within 10 seconds I was convinced I needed to try this.
For me, the next step for this is taking all the sensor data recorded for a ride, and loading it into my own fitness tracking database that I own, control, and isn't tied to someone else's profits.
- mholt
This is great, I just saw your post on X. I'm also building a bike computer!
eInk is the right display tech. I think this will do really well. It might need a UV filter.
That said, I don't love needing a separate device (hence, I don't own any bike computer). This is just my preference, but I really prefer to just plop my phone on my handlebars. So I'm building a bike computer app for iPhone: https://x.com/mholt6/status/2090529441944687087 (trying to get Apple to approve my developer account / business info, but they're hung up on my website of all things).
Phones are definitely not ideal in terms of display and energy use, but, I have found that with proper optimizations, energy use is a non-issue. To offset display problems, the app has several ride modes: a rich map display with 3D road or satellite view; a high-contrast wireframe map that looks great at both high and low refresh rates because it has no analog-style gauges; an instrument panel dashboard view; and a voice-only mode that has big touch zones for on-demand voice updates, using a state of the art mobile voice synthesis model. For connected radars, the app also renders radar data and has a screen like Tesla/Rivian's autonomy displays.
The app automatically manages thermals by switching modes to preserve battery life.
In my testing so far, by managing energy, making really good voice feedback, and using high-contrast screens (every mode other than the "rich" map), even a dimmed iPhone display is quite a usable bi […]
- grbi
Great project.
I'm tired of all the brands that stops updates ect.
Do you have a mounting system already ?
- lostlogin
Wow, amazing work.
My use case is a bit more basic than most. I am nearly always on routes I know and just want a few basic stats, but…
I require a bike radar to work. I use a Varia. I like the beep, and need the indication for a car behind. Is there any compatibility with this?
If this question is already answered somewhere, apologies.
- wiether
I love my eInk displays, I love my bike head unit.
But I don't see how they both fit together honestly.
The pros of eInk:
- low energy usage -> don't matter, current GPS units have +30 hours of battery life already
- low eye strain -> don't matter, you don't look at the screen for hours at a time
- visibility -> don't matter, current GPS units adapt to ambient light
- angle visibility -> don't matter, the screen is right in front of you
The cons of eInk:
- refresh rate -> yeah, I don't want the map display to be laggy
- visibility in the dark -> tunnels, tree cover... I don't want to my GPS to be invisible
- lack of color -> colors provide lots of information on the map display
Anyway, as long as you have fun doing this and some people enjoy it also, congrats!
- dongking
This exchange is fantastic! I was immediately impressed, and I'm eager to try it out with my bicycle.
- rjrjrjrj
Cool project. Not sure I'd use it, as my iPhone works quite well for this purpose. iPhones have had always on display since the 14 Pro and 17, and they've had good water resistance since forever. No problem reading it under any conditions.
- iPhone 15 Pro with quadlock case
- various Quadlock mounts
- Quadlock mag charging mount with a USB C battery in the top tube bag for long rides
- Apple Watch (paired to SRAM Powermeter on bike)
- Record rides using Apple Fitness on Apple Watch
- Apple fitness syncs to Strava and other services
- Ride With GPS, Apple Maps, or Google Maps for turn-by-turn (when necessary)