PX4 Instructions

ARK FlowPX4 Autopilot

Most up to date PX4 Documentation

Hardware Setup

Wiring

The ARK Flow is connected to the CAN bus using a Pixhawk standard 4 pin JST GH cable. For more information, refer to the CAN Wiring instructions.

Mounting

The recommended mounting orientation is with the connectors on the board pointing towards back of vehicle, as shown in the following picture.

ARK Flow align with Pixhawk

This corresponds to the default value (0) of the parameter SENS_FLOW_ROT. Change the parameter appropriately if using a different orientation.

The sensor can be mounted anywhere on the frame, but you will need to specify the focal point position, relative to vehicle centre of gravity, during PX4 configuration.

Firmware Setup

ARK Flow runs the PX4 DroneCAN Firmware. As such, it supports firmware update over the CAN bus and dynamic node allocation.

ARK Flow boards ship with recent firmware pre-installed, but if you want to build and flash the latest firmware yourself see PX4 DroneCAN Firmware > Building the Firmware.

• Firmware target: ark_can-flow_default

• Bootloader target: ark_can-flow_canbootloader

Flight Controller Setup

The ARK Flow will not boot if there is no SD card in the flight controller when powered on.

Connect the ARK Flow CAN to the flight controller's CAN port. Once parameters are set the module will be detected on boot. See DroneCAN > Enabling DroneCAN for more detail.

Flight Controller Parameters

Set the following in QGroundControl and reboot the flight controller.

Required

Parameter	Value	Description
UAVCAN_ENABLE	2	Enable DroneCAN with dynamic node allocation (use 3 if also driving DroneCAN ESCs)
EKF2_OF_CTRL	1	Enable optical flow fusion in the EKF
UAVCAN_SUB_FLOW	1	Subscribe to DroneCAN optical flow messages
UAVCAN_SUB_RNG	1	Subscribe to DroneCAN range finder messages
EKF2_RNG_A_HMAX	10	Max range used by the EKF
EKF2_RNG_QLTY_T	0.2	Range finder quality time
UAVCAN_RNG_MIN	0.08	Min reported range
UAVCAN_RNG_MAX	30	Max reported range
SENS_FLOW_MINHGT	0.08	Min height for optical flow fusion
SENS_FLOW_MAXHGT	25	Max height for optical flow fusion
SENS_FLOW_MAXR	7.4	Max angular flow rate (PAW3902 limit)

Optional

Parameter	Description
UAVCAN_SUB_IMU	Set to 1 to subscribe to DroneCAN RawIMU messages. Requires CANNODE_PUB_IMU to also be set on the ARK Flow
EKF2_GPS_CTRL	Set to 0 to disable GPS aiding (e.g. indoor flight)
EKF2_OF_POS_X / EKF2_OF_POS_Y / EKF2_OF_POS_Z	ARK Flow offset from the vehicle center of gravity (meters)
SENS_FLOW_ROT	Sensor rotation if mounted in a non-default orientation (default 0)

CAN Node Parameters

Optical flow and range finder messages are published by the ARK Flow by default — no CAN node parameters are required for those streams.

Set the following on the sensor and reboot the node. CAN node parameters can be configured using either:

• QGroundControl — each CAN node appears as a separate Component X entry under Vehicle Settings > Parameters.

• The DroneCAN GUI Tool.

Optional

Parameter	Description
CANNODE_TERM	Set to 1 if this is the last node on the CAN bus
CANNODE_PUB_IMU	Set to 1 to publish RawIMU messages on the CAN bus. Pair with UAVCAN_SUB_IMU on the flight controller