Hex HereFlow Optical Flow Sensor¶
The HereFlow optical flow sensor is a lightweight optical flow sensor including a short range lidar which uses the CAN protocol to communicate with the autopilot. This can be used to improve horizontal position control especially in GPS denied environments.
The lidar included with the HereFlow is very short range especially outdoors. We strongly recommend using a longer range lidar instead.
Connection to Autopilot¶
- The flow sensor should be mounted on the underside of the copter with the camera lens pointing downwards. The side of the sensor with the lens should be towards the front of the vehicle.
- Connect the sensor to the autopilots’ CAN port (if using a Cube note that pre-Apr 2019 boards have CAN1 and CAN2 swapped)
- Set FLOW_TYPE = 6 (DroneCAN)
- Set CAN_P1_DRIVER = 1 to enable DroneCAN
- Set CAN_D1_PROTOCOL = 1 (DroneCAN)
To use the onboard lidar (not recommended):
- As with the PX4Flow sensor a range finder is required to use the sensor for autonomous modes including Loiter and RTL
- FlowHold does not require the use of a rangefinder
- Performance can be improved by setting the sensors position parameters. For example if the sensor is mounted 2cm forward and 5cm below the frame’s center of rotation set FLOW_POS_X to 0.02 and FLOW_POS_Z to 0.05.