Setting Up Linux USB Ethernet Networking

Connecting to a Linux Host

Before doing anything, check to see what the existing network devices are on your Linux host:

user@machine:~$ ls /sys/class/net
eth0  lo  wlan0

This is a reference for the next step, where we plug the host end of the cable into the Linux machine and check if any new network devices showed up...

user@machine:~$ ls /sys/class/net
eth0  lo  usb0  wlan0

Great, we got a new device at usb0, as expected. If you did NOT see the device, then make check dmesg to see what happened ... the last few lines should look like this:

[ 3402.872886] usb 2-1.2.3: new full-speed USB device number 54 using ehci_hcd
[ 3402.965691] usb 2-1.2.3: not running at top speed; connect to a high speed hub
[ 3402.967534] usb 2-1.2.3: New USB device found, idVendor=0525, idProduct=a4a2
[ 3402.967541] usb 2-1.2.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 3402.967547] usb 2-1.2.3: Product: RNDIS/Ethernet Gadget
[ 3402.967552] usb 2-1.2.3: Manufacturer: Linux 3.3.0 with musb-hdrc
[ 3402.974822] cdc_eem 2-1.2.3:1.0: usb0: register 'cdc_eem' at usb-0000:00:1d.0-1.2.3, CDC EEM Device, 2a:7a:91:09:c5:b6

Maybe double check to make sure you updated the ev3dev.rc.local file on the FAT32 partioin of the microSD card. Also check to see if you have the cdc_eem and cdc_subset modules available for your host machine.

Now it's a simple matter to configure an IP address for the Host end of the connection. I'm assuming you left the default value of the EV3 IP address at 192.168.2.100 in the ev3dev.rc.local file. just do something like:

sudo ifconfig usb0 192.168.2.1

Of course, you'll use the actual new usbx value you see when you connect the EV3 to your host machine.

Now you can ping the brick like this:

user@machine:~/nfs/ev3dev/ev3dev-rootfs$ ping 192.168.2.100
PING 192.168.2.100 (192.168.2.100) 56(84) bytes of data.
64 bytes from 192.168.2.100: icmp_seq=1 ttl=64 time=1.48 ms
64 bytes from 192.168.2.100: icmp_seq=2 ttl=64 time=0.826 ms
64 bytes from 192.168.2.100: icmp_seq=3 ttl=64 time=0.850 ms
64 bytes from 192.168.2.100: icmp_seq=4 ttl=64 time=0.812 ms
^C
--- 192.168.2.100 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3002ms
rtt min/avg/max/mdev = 0.812/0.992/1.481/0.283 ms

And you can ssh to it like this:

user@machine:~/nfs/ev3dev/ev3dev-rootfs$ ssh root@192.168.2.100
root@192.168.2.100's password: 
Linux ev3dev 3.3.0 #4 PREEMPT Sat Dec 7 13:12:33 EST 2013 armv5tejl
             _____     _
   _____   _|___ /  __| | _____   __
  / _ \ \ / / |_ \ / _` |/ _ \ \ / /
 |  __/\ V / ___) | (_| |  __/\ V /
  \___| \_/ |____/ \__,_|\___| \_/

Debian GNU/Linux 7 on LEGO MINDSTORMS EV3!

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Sat Jan  1 00:04:26 2000
root@ev3dev:~# 

Once you have confirmed that this all works, you can automagically set the IP address of your host computer when a USB Ethernet connection. Just edit /etc/network/interfaces and add this stanza to the file:

allow-hotplug usb0
auto usb0
iface usb0 inet static
         address 192.168.2.1
         netmask 255.255.255.0

That's all for now.

Share Internet Connection from Linux Host

If you want to share the Internet connection from your host PC with the EV3 via USB, enable forwarding on your host PC:

echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward > /dev/null
sudo iptables -P FORWARD ACCEPT
sudo iptables -A POSTROUTING -t nat -j MASQUERADE -s 192.168.2.0/24

And use your router as the name server on the EV3:

echo "nameserver 192.168.0.1" >> /etc/resolv.conf

Then you can test the Internet connection on the EV3:

ping google.com

Forwarding the Internet connection can also be deactivated on your host PC:

echo 0 | sudo tee /proc/sys/net/ipv4/ip_forward > /dev/null
sudo iptables -t nat -F POSTROUTING

The description for forwarding the Internet connection is based on the article from https://developer.ridgerun.com/wiki/index.php/How_to_use_USB_device_networking#Bridging_host_PC_to_allow_device_to_reach_the_Internet.

Later on we'll discuss getting your EV3 connected to the Internet via wifi.