HOLYBRO H-Flow (Optical Flow and Distance Sensor Module)

HOLYBRO H-Flow – Optical Flow and ToF Distance Sensor with DroneCAN

The HOLYBRO H-Flow is a compact sensor for optical motion and distance measurement in UAVs and other unmanned systems. The module combines a PixArt PAA3905E1 optical flow sensor, a Broadcom AFBR-S50LV85D Time-of-Flight distance sensor, and an InvenSense ICM-42688-P 6-axis IMU in a single housing.

By combining optical flow, distance measurement, and IMU data, the H-Flow can support the flight controller in determining position and motion. This is particularly useful for indoor flights or other environments where a reliable GNSS signal is not available.

An integrated infrared LED improves the operating conditions of the optical flow sensor in low ambient light. Communication with the flight controller is handled via DroneCAN and a Pixhawk-standard CAN connection with a 4-pin JST-GH connector.

Optical Flow and Distance Measurement in One Module

The H-Flow combines multiple sensors in a compact unit. This simplifies integration into UAV platforms and eliminates the need to install separate optical flow, distance, and motion sensors.

• PixArt PAA3905E1 optical flow sensor
• Broadcom AFBR-S50LV85D Time-of-Flight distance sensor
• InvenSense ICM-42688-P 6-axis IMU
• Integrated infrared LED
• STM32F412CEU6 microcontroller
• DroneCAN communication

PixArt PAA3905E1 Optical Flow Sensor

The integrated PixArt PAA3905E1 detects motion relative to the surface below. These data can be used by the flight controller to determine horizontal movement and can support position control in environments without reliable satellite-based navigation.

• Sensor: PixArt PAA3905E1
• Minimum Illumination: above 5 lux
• Effective Field of View: up to 42°
• Operating Range: 80 mm to 30 m
• Maximum Angular Velocity: up to 7.4 rad/s

Infrared LED for Low Ambient Light

To support the optical flow sensor in poor lighting conditions, the H-Flow features an integrated 40 mW infrared LED. It has a 120° beam angle and improves optical detection in low ambient light.

• Power: 40 mW
• Beam Angle: 120°
• Integrated directly into the H-Flow
• Supports optical flow operation in low-light conditions

Broadcom Time-of-Flight Distance Sensor

For distance measurement, the H-Flow uses a Broadcom AFBR-S50LV85D Time-of-Flight sensor. The sensor uses an integrated 850 nm laser light source and provides a typical distance measurement range of up to 30 meters.

The distance measurement complements the optical flow data with information about the distance to the detected surface. This allows motion and distance data to be used together for navigation and position control.

• Sensor: Broadcom AFBR-S50LV85D
• Measurement Principle: Time-of-Flight (ToF)
• Laser Wavelength: 850 nm
• Typical Range: up to 30 m
• Field of View: 12.4° × 6.2°
• Resolution: 32 pixels
• Ambient Light: operation up to 200,000 lux
• Emitter Beam: 2° × 2°
• Designed for different surface conditions

Integrated 6-Axis IMU

In addition to optical flow and distance measurement, an InvenSense ICM-42688-P 6-axis IMU is integrated. It provides acceleration and angular rate data and complements the module's optical sensor data.

• IMU: InvenSense ICM-42688-P
• 3-axis accelerometer
• 3-axis gyroscope

DroneCAN Communication

Communication between the H-Flow and the flight controller is handled via the DroneCAN protocol. CAN-based data transmission provides robust digital communication and simplifies integration into compatible autopilot systems.

A Pixhawk Standard CAN Connector with a 4-pin JST-GH connector is provided for connection.

• Protocol: DroneCAN
• Connection: Pixhawk Standard CAN
• Connector: 4-pin JST-GH
• CAN Termination: software-controlled

STM32F412 Microcontroller

Sensor data processing and DroneCAN communication are handled by an integrated STM32F412CEU6 microcontroller. This combines the various sensors within the H-Flow into one compact sensor module.

Compact and Lightweight Design

The H-Flow has been designed for space- and weight-efficient integration. The complete module weighs only 15.2 g including the housing. Without the housing, the weight is just 3.5 g.

• Weight with Housing: 15.2 g
• Weight without Housing: 3.5 g

Support for GNSS-Independent Navigation

The combination of optical flow, distance measurement, and IMU data makes the H-Flow particularly useful for applications where positioning cannot rely exclusively on GNSS. Examples include indoor flights, large halls, technical facilities, and other shielded environments.

The H-Flow does not generally replace a complete navigation solution. Instead, it provides the flight controller with additional motion and distance information that can be used for position control and navigation depending on the autopilot configuration.

Features

• Combined optical flow and distance sensor module
• PixArt PAA3905E1 optical flow sensor
• Broadcom AFBR-S50LV85D Time-of-Flight sensor
• InvenSense ICM-42688-P 6-axis IMU
• Typical distance measurement up to 30 m
• Optical flow operating range from 80 mm to 30 m
• Integrated 40 mW infrared LED
• Improved operation in low ambient light
• STM32F412CEU6 microcontroller
• DroneCAN communication
• Pixhawk Standard CAN connection
• 4-pin JST-GH connector
• Software-controlled CAN termination
• Compact and lightweight design

Technical Specifications

• Optical Flow Sensor: PixArt PAA3905E1
• Optical Flow Field of View: up to 42°
• Optical Flow Operating Range: 80 mm to 30 m
• Optical Flow Light Requirement: > 5 lux
• Maximum Angular Velocity: 7.4 rad/s
• IR LED: 40 mW / 120°
• Distance Sensor: Broadcom AFBR-S50LV85D
• Measurement Principle: Time-of-Flight
• Laser Wavelength: 850 nm
• Typical Distance Range: up to 30 m
• ToF Field of View: 12.4° × 6.2°
• ToF Resolution: 32 pixels
• Ambient Light: up to 200,000 lux
• IMU: InvenSense ICM-42688-P 6-axis
• Microcontroller: STM32F412CEU6
• Communication: DroneCAN
• CAN Connection: Pixhawk Standard 4-pin JST-GH
• CAN Termination: software-controlled
• Weight: 15.2 g with housing
• Weight without Housing: 3.5 g

Package Contents

• 1 × HOLYBRO H-Flow
• 1 × 4-Pin GH Cable
• 2 × M2.5 Screws
• 2 × M2.5 Nylon Lock Nuts

Optical Flow for UAVs and Autonomous Systems

The HOLYBRO H-Flow combines three important sensor technologies in a compact module: optical flow for motion detection, Time-of-Flight for distance measurement, and a 6-axis IMU for measuring acceleration and angular rates.

With DroneCAN, a Pixhawk-compatible CAN connection, and its compact design, the H-Flow is particularly suitable for UAVs, robotics platforms, and custom unmanned systems that require additional sensor data for precise motion and position estimation.