Show HN: Open-Source eInk Bike Computer

Original Article ↗ Hacker News Discussion ↗

An open‑source e‑ink bike computer is drawing interest from cyclists who want a dedicated, hackable alternative to commercial head units and phone mounts. Commenters weigh the trade‑offs of e‑ink versus transflective LCDs and smartphone screens—readability in sun, refresh rates, fragility, UV and weather resistance, night visibility, and battery life—alongside integration with ANT+ and BLE sensors, GPS, and radars like Garmin Varia. Many see value in an independent, customizable device that avoids vendor lock‑in and phone wear, even if matching the durability and polish of Garmin or Wahoo units will be challenging.

Overall reception

  • Many commenters find the open-source eInk bike computer “very cool” and exciting, especially as an alternative to closed Garmin/Wahoo ecosystems and abandoned proprietary devices.
  • Others are unsure who the target user is, arguing that existing bike computers and phones already solve the problem well.

Display tech: eInk vs LCD/transflective

  • Pro‑eInk:
    • Excellent readability in direct sun; behaves like paper and doesn’t try to “outbright” the sun.
    • Low power when the image is static; white background without constant backlight.
    • Some report modern eInk can reach ~20 Hz and is sufficient for bike navigation where 1 Hz updates are often enough.
  • Skepticism:
    • Existing bike computers with transflective LCDs already have great sunlight visibility and 30+ hour battery life; eInk’s efficiency is seen as unnecessary.
    • Concerns about low inherent contrast (spec numbers like 12–20:1 vs ~500:1 LCD) and lack of color for maps.
    • Night/tunnel visibility requires a backlight; some doubt it’ll match emissive displays.
    • Questions about refresh rate for smooth maps and motorcycle-like navigation.
  • Disagreement over real‑world contrast: some insist eInk is clearly superior outdoors; others argue measured contrast limits and low dynamic range vs the sunlit environment.

Durability, weather, and sunlight exposure

  • Concerns about use in rain (e.g., Netherlands), winter, and general ruggedness.
  • Some note eInk panels they’ve used are fragile and can be damaged by vibration, drops, UV, and heat; UV blocker is recommended.
  • Others describe practical methods for weather sealing 3D‑printed cases (strong filament, lacquer, lots of glue) and say similar devices have survived heavy rain.

ANT+, BLE, and protocol hacking

  • Strong interest in the ANT+ implementation over BLE hardware; clarified that they share the same 1 Mbps GFSK physical layer but different protocols.
  • Several note ANT+’s rich cycling sensor ecosystem (speed/cadence, power, HR, radar, lights, trainers) but say EU encryption rules have effectively killed new ANT+ devices, pushing everything toward BLE.
  • Commentary that BLE devices often still broadcast unencrypted data in practice.
  • Some mention existing open-source work on other e‑bike protocols (UART, CAN) and that logic analyzers + LLMs make reverse‑engineering easier.

Phone vs dedicated head unit

  • Phone‑centric view:
    • Modern phones (e.g. iPhones with always‑on displays) plus mounts and external batteries work well for many.
    • Custom apps can optimize energy, manage thermals, provide high‑contrast or voice‑only modes, and integrate radar.
  • Dedicated computer view:
    • Avoid draining or overheating the phone, especially on long rides, bikepacking, or multi‑day events.
    • Protect the phone (and its OIS camera) from vibration damage, falls, theft, and weather.
    • Some report actual camera failures on bar‑mounted phones; vibration‑damping mounts help but don’t fully reassure everyone.

GPS, sensors, and future features

  • Current telemetry relies on GPS; commenters suggest adding ANT+ wheel sensor support for better speed/distance accuracy and lower power.
  • Radar (e.g. Varia‑style) support is seen by some as a “must have” safety feature.
  • Interest in integrating with self‑hosted tracking (e.g., custom fitness databases) and open tools like Gadgetbridge/Endurain.
  • A GPS tracker use case is mentioned (cheap tracker + SIM + Traccar) as a different solution space.

Form factor and mounting

  • Some feel the 4.7" display is too large for a head unit; others like the readability and uniqueness vs existing small transflective devices.
  • Requests for larger buttons, smaller overall footprint, and robust, standardized mounts.
  • Ideas surface for headset‑integrated computers and in‑steerer storage, though practical mechanical constraints are noted.