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The BMK GPS Tracking System
A complete radio-telemetry solution for free-flight model aircraft. Your model carries a tiny GPS beacon; you carry a handheld receiver that shows live altitude, distance, bearing — and stores every flight to memory.
The system has two parts:
- Alti-Loc GPS Beacon — lightweight, low-power transmitter with built-in GPS and altimeter. Mounts in the model.
- FlexiDisplay Yello Hand Unit — handheld receiver with sunlight-readable LCD, 434 MHz transceiver, barometer, 9-axis IMU, magnetic compass, GPS, BLE 4.0 and onboard flight recorder.
📄 Documentation
- FlexiDisplay Yello — Product Manual (PDF) — covers setup, all five display modes, settings menu, channel scanner, flight recorder, app pairing, and troubleshooting.
- FlexiDisplay v1 manual (legacy)
🧩 Firmware Updates
FlexiDisplay Yello supports over-the-air firmware updates directly from the BMK Model Locator app — no cable, no PC.
Legacy v1 firmware releases: GitHub repository.
📱 BMK Model Locator App
The FlexiDisplay Yello pairs over Bluetooth 4.0 with the BMK Model Locator app, giving you a full map view of every beacon, compass-rotated searchlight navigation, altitude analysis graphs, remote device settings, and one-tap flight log download as CSV or KML.
🎥 Demo Video
✨ What's new in FlexiDisplay Yello (v2)
- Find FD Units — every Yello broadcasts its own GPS position once a minute. If you ever misplace a hand unit, another Yello will show you where it is
- 2 MB flight recorder with FAT file system — download full flights to the app as CSV or KML
- BLE 4.0 OTA updates — firmware refresh in under 60 seconds, no cable
- Auto Low-Power GPS — extends battery life when the device is stationary, resumes the moment you move it
- Barometer — live pressure, temperature, and barometric altitude on the hand unit itself
🛠️ Full Feature List
FlexiDisplay Yello Hand Unit
- Display: 96 × 64 sunlight-readable LCD with adjustable backlight (0–10)
- Radio: Semtech SX1268 — 434 MHz FSK for beacons, LoRa for FD-to-FD location broadcast
- Channels: 60 channels (434.000–435.475 MHz, 25 kHz spacing)
- Sensors: Barometer, 6-axis IMU, Magnetic compass, Quectel L96-M33 GPS (GPS + GLONASS + BeiDou)
- Connectivity: Bluetooth 4.0
- Flight recorder: 2 MB SPI flash, FAT filesystem, up to 2,000 records per flight
- Battery: Built-in LiPo, USB 5 V charging, up to 80 hours runtime
- Joystick + RED button — full menu navigation, settings, calibration, OTA
Alti-Loc GPS Beacon
- Power usage: 30 mA in flight, 7 mA when stationary
- Adaptive update rate: 0.5 s climbing, 1 s cruise, 8 s stationary
- Range: Over 20 km in-air under UK conditions
- Last-known position: Retained on the display even if the beacon drops out
- Low-battery mode: Below 3.3 V the beacon disables GPS and transmits its last known position to save power
- GPS quality indicator: Visual alert when accuracy drops below ~10 m
- RDT trigger compatible: Works with BMK B1 and B2 remote DT transmitters
App & Workflow
- Multi-beacon tracking: Up to 20 beacons on one screen — your own and others nearby
- Compass-rotated map: Searchlight indicator points toward the active beacon
- Altitude analysis: Per-flight altitude/climb/sink graphs with comparison mode
- Flight log export: One-tap download from device to phone as CSV or KML
- QR-coded location: Scan from the hand unit to open the last beacon position in Google Maps
- Remote device settings: Change radio channel, beacon name, RDT code from the app
Designed and built in the UK by BMK. Specifications subject to firmware updates — keep your device current via the app for the latest features.