Field notes for building on smart glasses.
Measured specs, working code and a lens simulator for display glasses — written down while shipping real apps on them. The code is open source on GitHub. No marketing numbers: everything here was tested on the hardware.
$ b-d preview "hello, lens"
hello, lens
576×288 · 27 px line · 9 rows
Devices
What each pair actually lets a third-party app do. Full comparison →
| Glasses | Display | Text canvas for apps | Mic to phone | Access |
|---|---|---|---|---|
| Even Realities G2 | Both lenses, 576×288 | yes text boxes, ~27 px lines | LC3 frames | Community BLE protocol; official Even Hub SDK |
| RayNeo iO | Yes | no template screen; firmware does the layout | Opus 16 kHz (long streams unverified) | Protocol reachable; display not open |
| Meta Ray-Ban Display | Right lens | yes through Meta's display API | Camera-stream audio only (experimental) | Official Wearables Device Access Toolkit |
Notes
Problems we had to solve to ship live captions on glasses.
- Reconnect like headphonesWhy bonded glasses stop advertising, and how pending connections bring them back without the vendor app.
- Captions that don't flickerLaying out lines on the phone, scrolling one line at a time, updating only what changed.
- Glyph widths and line breaks soonMatching the firmware's own wrapping so text never reflows on the lens.
- Keeping the link alive soonHeartbeats, background modes and lock screen on iOS and Android.
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