Autopilot Connections

There are two communication channels between the Jetson and the flight controller: USB and serial. Both are direct board-to-board connections tested up to 3 Mbps.

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

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

USB

The flight controller's USB connection is muxed with the external Micro USB port. While a Micro USB cable is connected, the flight controller is disconnected from the Jetson. After unplugging, reboot the Jetson to restore the connection.

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.

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)