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Version: 2.0 (Legacy)

Bidirectional Telemetry

OpenHD 2.0 supports full bidirectional telemetry communication with flight controllers.

Overview​

Bidirectional telemetry allows:

  • Downlink: Flight controller data to ground station
  • Uplink: Commands from ground station to flight controller
  • Real-time Parameter Changes: Modify flight controller settings remotely
  • Mission Planning: Upload waypoints and missions

Supported Protocols​

  • MAVLink v1: Legacy support
  • MAVLink v2: Recommended protocol with enhanced features
  • Parameter Management: Read and write flight controller parameters
  • Mission Protocol: Upload and download missions

Other Protocols​

  • MSP: MultiWii Serial Protocol support
  • LTM: Lightweight Telemetry
  • FrSky: FrSky telemetry protocol

Configuration​

Flight Controller Setup​

Configure your flight controller for telemetry output:

  • ArduPilot: Set SERIAL ports for MAVLink
  • Betaflight/INAV: Configure MSP or LTM output
  • PX4: Enable MAVLink on appropriate UART

OpenHD Configuration​

Configure telemetry settings in QOpen.HD:

  • Protocol Selection: Choose appropriate telemetry protocol
  • Baud Rate: Match flight controller settings
  • Port Configuration: Select correct UART port

Wiring​

UART Connection​

Connect flight controller to Raspberry Pi UART:

  • TX (FC) → RX (Pi GPIO 10)
  • RX (FC) → TX (Pi GPIO 8)
  • GND → GND
Voltage Levels

Ensure voltage compatibility between flight controller (typically 3.3V) and Raspberry Pi (3.3V). Some older flight controllers use 5V signaling.

Ground Control Station Integration​

QGroundControl​

  • Full parameter management
  • Mission planning
  • Real-time telemetry display

Mission Planner​

  • ArduPilot parameter tuning
  • Advanced mission planning
  • Log analysis

QOpen.HD​

  • Built-in telemetry display
  • Basic parameter access
  • Custom OSD elements
Bandwidth Considerations

Bidirectional telemetry uses uplink bandwidth. High-frequency parameter requests may impact RC control responsiveness.

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