USB device mode support

On the zeus and later branches (for L4T R32.2.3 and later), the l4t-usb-device-mode recipe is available to set up USB gadgets on a Jetson device for network and serial TTY access. The setup is similar to what's provided in the L4T/JetPack BSP, except:

• the scripts in the BSP under /opt/nvidia/l4t-usb-device-mode have been replaced by a combination of systemd, udev, and libusbgx configuration files;
• the USB device identifier uses the Linux Foundation vendor ID; and
• no mass storage gadget is created

Note that as of this writing, support for creating both an ECM gadget and an RNDIS gadget is provided, but the RNDIS gadget has not been tested.

Prerequisites

1. You must have the meta-oe layer from meta-openembedded in your build for the libusbgx recipe.
2. You must use systemd, and include udev and networkd support in its configuration (both of which are on by default in OE-Core zeus).

Network configuration

The systemd-networkd configuration files provided automatically create an l4tbr0 bridge device that combines the usb0 ECM interface and the rndis0 RNDIS interface. The bridge is assigned the IP address 192.168.55.1 and runs a DHCP server to serve the address 192.168.55.100 to the host side of the USB connection.

Serial port configuration

The serial port is called /dev/ttyGS0 on the device, and a udev rule automatically starts serial-getty on the device when it is created. If the connecting host is running Linux, the corresponding serial TTY will be /dev/ttyACM0 (or another /dev/ttyACMx device if there are multiple such devices on your host system).

Using device mode support

To use device mode support, just include l4t-usb-device-mode in your image.