Autopilot Connections

There are three communication channels between the Jetson and the flight controller: USB, serial, and Ethernet. USB and serial are direct board-to-board connections tested up to 3 Mbps; Ethernet runs through the onboard 100 Mbps switch.

Type	Jetson device path	Flight Controller
USB	/dev/ttyACM0	USB
Serial	/dev/ttyTHS1	Telem2
Ethernet	enP8p1s0	eth0

We recommend running MAVLink on USB and XRCE-DDS on serial. ARK-OS's defaults do exactly this — see Services.

USB

For the flight controller's USB to enumerate, its VBUS_SENSE pin must be driven high by the Jetson. This is set in the Jetson pinmux at boot, so it works out of the box.

Serial

The serial connection is Jetson UART1 (/dev/ttyTHS1) to Telem2 on the flight controller, tested to 3 Mbps. When running MAVLink on Telem2, set flow control to off: MAV_x_FLOW_CTRL = 0.

Ethernet

The flight controller and Jetson are connected through a 100 Mbps switch on the board, along with two external connections: the 4-pin JST-GH Ethernet connector and the Pixhawk Payload Bus FFC.

To set up the flight controller side, follow the PX4 Ethernet guide or the ArduPilot network guide. If one of the external connections leads to a router running DHCP, both the Jetson and flight controller get addresses from it; otherwise configure static IPs on both ends.

Flight Controller Reset

The Jetson can hard-reset the flight controller via a GPIO reset line. The reset is gated by the nARMED signal — the Jetson cannot reset the flight controller while it is armed.

ARK-OS ships two reset helpers on PATH:

reset_fmu_fast.py       # reset and boot straight into the application
reset_fmu_wait_bl.py    # reset and wait in the bootloader (for firmware flashing)