Holybro PMW3901 Optical Flow Sensor

Holybro's PMW3901 optical flow sensor tracks ground texture to measure how the drone is drifting, giving PX4 and ArduPilot multirotors position hold without GPS — indoors, under cover or close to the ground. It talks UART and plugs straight into a flight controller TELEM port.

Key features

• Plug-in wiring — pre-soldered 6-pin JST-GH cable (170mm) for a standard TELEM port.
• Onboard regulator — accepts 3.3–5.2V and draws about 10mA.
• 95Hz updates of X/Y motion plus a surface-quality value for the autopilot's estimator.
• Tiny footprint — 14 x 11 x 5mm and 0.6g, with a TPU case included.
• CX-OF data format — the same protocol as the discontinued CX-OF sensor, so the existing PX4 and ArduPilot drivers handle it.

Specifications

• Sensor: PixArt PMW3901
• Interface: UART, 19200 baud
• Input voltage: 3.3–5.2V
• Current draw: 10mA
• Update rate: 95Hz
• Dimensions: 14 x 11 x 5mm
• Weight: 0.6g
• Connector: JST-GH 6-pin, 170mm cable
• In the box: sensor, GH 6-pin cable, TPU case

Optical flow needs height above ground to turn image motion into speed, so pair it with a downward-facing rangefinder. Mount it pointing straight down with a clear view, away from props and landing gear, and fly over textured, well-lit surfaces — plain glossy floors give poor readings.