Unable to connect to X20 via adb

I am unable to connect to my new X20 boards via adb:
$ sudo adb devices -l returns nothing when an X20 board is connected; the same works fine with my HiKey and DragonBoard CE boards.

For HiKey, I have the following magic incantations in the /etc/udev/rules.d/51-android.rules file on my host machine:

# fastboot protocol on HiKey
SUBSYSTEM=="usb", ATTRS{idVendor}=="18d1", ATTRS{idProduct}=="d00d", MODE="0666"
# adb/rndis protocol on HiKey
SUBSYSTEM=="usb", ATTRS{idVendor}=="12d1", MODE="0666", ENV{ID_MM_DEVICE_IGNORE}="1"

Is there similar magic for X20?

By the way, I’ve got the first (AUTO_BOOT_SET) and third (USB_HOST_SET) pins at the back of the boards enabled as per the Getting Started instructions, and tried with and without the keyboard and mouse connected.

Oh my, I guess the USB_HOST_SET pin is called so for reason! It seems it should be disabled for adb to work over USB:


I have my two boards stacked, which makes only one set of switches readily accessible. I hope I can set up adb to work over WiFi: