SSH in to an EV3 running leJOS using the USB cable

I have underestimated leJOS at every turn, never more so than the issue of connectivity. I got Wifi to work by editing files directly on the SD card. That it worked is a testament both to leJOS and my own stubbornness. It turns out, however, that there is a much easier way of gaining SSH access to an EV3 running leJOS.

Simply use the mini-USB cable that ships with the EV3, connect the EV3 to your Linux machine and wait for the USB Ethernet connection to be established automatically (tested on Ubuntu where a desktop notification appears to indicate this). Run ifconfig to confirm that the usb0 network interface is up and running.

The EV3 displays its IP address on the home screen: 10.0.1.1. Simply SSH in to this address using username root and a blank password. Could it be more painless?

Connecting to an EV3 running LeJOS using Bluetooth

I had known all along that the EV3 comes equipped with Bluetooth and that LeJOS allowed you to write programs that employed Bluetooth for communication, but the whole truth is way cooler.
I learned only recently that with Bluetooth activated, LeJOS running on the EV3 implements a Bluetooth PAN (Personal Area Network) by becoming a GN (Group ad-hoc Network) Controller.
This means the EV3 is acting as a server on a bluetooth-based network. You can connect your computer to this network using bluetooth. The computer acts as a PANU (a client of the PAN) and is able to ssh in to the EV3 and perform all of the actions we were performing using the WiFi dongle. The immediate advantage is that one does NOT need the WiFi dongle (saves money and you don't have the dongle protruding off of the side of the EV3).
Bluetooth on Linux (my experience is with Ubuntu 12.04 and 13.04) is still buggy but the setup for connecting to the EV3 was surprisingly painless once I figured it out (that part was harder).
The first step is to confirm that bluetooth is running on your computer by running the following command in a terminal:

hciconfig -a

This will spit out a bunch of information:

hci0: Type: BR/EDR  Bus: USB
 BD Address: 00:16:CF:FE:03:A0  ACL MTU: 1017:8  SCO MTU: 64:8
 UP RUNNING PSCAN ISCAN 
 RX bytes:301012 acl:2298 sco:0 events:460 errors:0
 TX bytes:94808 acl:966 sco:0 commands:67 errors:0
 Features: 0xff 0xff 0x8d 0xfe 0x9b 0xfd 0x00 0x80
 Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
 Link policy: RSWITCH HOLD SNIFF PARK 
 Link mode: SLAVE ACCEPT 
 Name: 'Abid-Laptop'
 Class: 0x6e010c
 Service Classes: Networking, Rendering, Capturing, Audio, Telephony
 Device Class: Computer, Laptop
 HCI Version: 2.0 (0x3)  Revision: 0x20da
 LMP Version: 2.0 (0x3)  Subversion: 0x4182
 Manufacturer: Broadcom Corporation (15)

Look for "Networking" in 'Service Classes' and "Computer" in 'Device Class'. In addition we need a useful 'Name'. To change it issue:

sudo hciconfig hci0 name '<device name>'

To connect to the EV3 (running LeJOS) turn it on and navigate to the "Bluetooth" menu. Make sure that it says "Visibility on". Now on your computer issue:

hcitool scan

The response should look like:

Scanning ...
 00:16:53:40:E9:7D EV3

We will need the Bluetooth address of the EV3 (the 12 hexadecimal number interspersed with colons) and the IP address of the EV3 on the PAN (displayed on the EV3 screen - 10.0.1.1 in my case). To connect to the EV3 as a PANU client one uses the pand utility (from the bluez-compat package):

sudo pand --connect 00:16:53:40:E9:7D

The PAN has been established but we need to start the bnep0 network interface manually on the computer to allow us to access the EV3 over the bluetooth PAN. Since the EV3 has IP address 10.0.1.1 we choose for our computer 10.0.1.2 (the first three numbers (sub-domain) need to match, the last one can be any number from 2 to 255):

sudo ifconfig bnep0 10.0.1.2

To confirm that the bnep0 network interface is active simply run:

ifconfig

and look for:

bnep0     Link encap:Ethernet  HWaddr 84:a6:c8:9b:ce:58  
          inet addr:10.0.1.2  Bcast:10.255.255.255  Mask:255.0.0.0
          inet6 addr: fe80::86a6:c8ff:fe9b:ce58/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:670 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:30820 (30.8 KB)  TX bytes:428 (428.0 B)

To confirm connectivity with the EV3 we ping it:

ping -c3 10.0.1.1

One can ssh in to the EV3 using IP Address 10.0.1.1, username "root" and blank password:

ssh root@10.0.1.1

It helps with automation if you set up an SSH private/public key-pair and store the public key in /home/root/.ssh/authorized_keys allowing password-less access. Finally to disconnect the computer from the EV3 PAN issue:

sudo pand -K

Using make to build and deploy LeJOS programs on the EV3

As discussed earlier my aim is to automate the repetitive nature of the edit-build-deploy-run cycle for programming the EV3 using LeJOS. To that end I set up build.gradle to build the project from the command-line as explained here. Furthermore I set up wifi on the EV3 (using a usb dongle). The next step was to edit ~/.ssh/config and add an entry for the EV3:

  Host ev3

      User root
      HostName 192.168.1.16
      IdentityFile ~/.ssh/abid_ev3

Note: Since the wifi setup on the EV3 is DHCP (not static) the IP address is liable to change, in which event one has to modify ~/.ssh/config accordingly.

The next step is to create a Makefile in your project root. Here is a link to the one I'm using for my "Rover" project. Note the extensive use of PHONY and EMPTY targets to ensure that build and scp tasks are only performed when needed. make once correctly set up takes care of the dependencies. I only need to issue make run from the terminal and the source is compiled and the jar file copied to the EV3 only if needed. Sweet and simple, just the way I like it.

You can take a look at the complete Rover source code on github. There you will also find a number of other repos for my various LeJOS EV3 projects.

Setting up Wifi on an EV3 running LeJOS

What is the point of having an awesome robotics kit running Linux if you cannot access the shell? That is a question I found myself facing once I had installed LeJOS on the EV3. Although I could place programs (Java .jar files) on the sd card directly) and execute them on the EV3 this became quite tedious quite fast. Fortunately, of the few Wifi dongles supported by LeJOS is the Edimax EW-7811Un which sells for $10 at Amazon. This amazingly small wifi dongle is an excellent add-on for the EV3 and works on the Raspberry Pi as well.

Once again the internet is full off conflicting advice on how to get the EV3 running LeJOS to automatically detect the Wifi dongle (Note: The stock Lego EV3 firmware never did detect it). The advice that worked for me came from this source.

The common pitfalls to avoid are: do NOT edit /etc/network/interfaces (no matter how many tutorials tell you to), you only need to modify /etc/wpa_supplicant.conf. And you can generate the psk in hex form by running the wpa_passphrase command as follows:

    wpa_passphrase <SSID>

and simply enter the passphrase when prompted to get the psk in hex format.

In summary load the microSD card (with the LeJOS partitions for EV3) in to your computer, mount the non-boot partition and edit /etc/wpa_supplicant.conf to enter your wireless network credentials. Once done, unmount the microSD card and load it in to the EV3. Start it up (it should boot in to LeJOS) and the EV3 should connect automatically to your specified wireless network.

Note: Once wifi is set up you can ssh in to the EV3 using the IP Address displayed by LeJOS on the EV3's screen. The username is root and the password is blank/empty. To allow scripts to ssh in to the EV3 I placed my public key in the /home/root/.ssh/authorized_keys file (which I had to create) and then simply added an entry for EV3 in my computers ~/.ssh/config file. Now I can access my EV3 over wifi effortlessly.