Setup USB Gadget Ethernet on Beaglebone Black

Introduction

Here we want to enable network access between the target board and the host dev. Rather than use the ethernet interface (which may not always be available on the target) we can provide power and connect via ethernet to the target board using the USB interface and the USB Gadget framework provided by Linux. This article will explain how to enable this in the Linux Kernel using Yocto and then how to configure Linux on both target and host machines.

Here is an overview of the setup

So that the PCI and USB interfaces (“eth0” and “enxf8dc7a000001”) can both work at the same time, its a good idea to use a different subnet from the existing PCI wired interface. For example, my PCI interface is set to 192.168.1.192. Therefore we set the Host USB interface to 192.168.0.1

Setting up Yocto

1. Download Yocto kirkstone4.0.2 branch

   $ git clone https://git.yoctoproject.org/git/poky
   $ git checkout -b kirkstone-4.0.2 kirkstone-4.0.2
   $ source poky/oe-init-build-env
   

2. Enable the beaglebone-yocto machine in local.conf

   MACHINE ?= "beaglebone-yocto"
   

3. Enable setup hash equivalence server in local.conf

   BB_SIGNATURE_HANDLER = "OEEquivHash"
   BB_HASHSERVE = "auto"
   BB_HASHSERVE_UPSTREAM = "hashserv.yocto.io:8687"
   SSTATE_MIRRORS ?= "file://.* https://sstate.yoctoproject.org/all/PATH;downloadfilename=PATH"
   

4. Enable other build performance tweaks in local.conf

   BB_NUMBER_THREADS = "8"
   INHERIT += "rm_work"
   

Configuring the kernel

1. Start menuconfig

   $ source oe-init-build-env
   $ bitbake linux-yocto -c kernel_configme -f
   $ bitbake linux-yocto -c menuconfig
   

2. Include Ethernet Gadget by pressing “Y”

   

3. Save the config, exit menuconfig and build the yocto image

   $ bitbake core-image-minimal
   

   You can check the enabled options were used in the build atbuild/tmp/work/qemux86-poky-linux/linux-yocto/4.12.12+gitAUTOINC+eda4d18...
...967-r0/linux-qemux86-standard-build/.config

4. Insert the SDCard into the host and write the image

   $ wic write tmp/deploy/images/beaglebone-yocto/core-image-full-cmdline-beaglebone-yocto-xxxxxxxxxxxxxxxxxx.rootfs.wic /dev/sdb
   

5. Open the SDCard Boot partition, and add g_ether mac addresses to the APPEND kernel command line arguments in root/extlinux/extlinux.conf

   g_ether.dev_addr=f8:dc:7a:00:00:02 g_ether.host_addr=f8:dc:7a:00:00:01
   

6. Open the SDCard Root partition and add USB0 interface settings to /etc/network/interfaces

   auto usb0
   iface usb0 inet static
           address 192.168.0.2
           netmask 255.255.255.0
           network 192.168.0.0
           broadcast 192.168.0.255
   

   Note, without “auto usb0” the interface will not connect automatically during boot and will require manual bring up (using ifconfig usb0 192.168.0.2 up)

Running the BBB

6. Setup the host USB ethernet interface.

   $ nmcli con add type ethernet ifname enxf8dc7a000001 ip4 192.168.0.1/24
   

7. Insert the SDCard into the BBB and power on

   USB Gadget ethernet will be loaded during boot with these lines:

   g_ether gadget: Ethernet Gadget, version: Memorial Day 2008
   g_ether gadget: g_ether ready
   

   The host USB Interface should now spring into life and connect to the target:

8. You can now ping from either target <--> host.