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Raspberry Pi Installation (Java Server)
To coincide With the release of the Raspberry Pi 3, we thought it would be good to create a "How to" Guide for installing Signal K on a Raspberry Pi (RPi). This is being written whilst installing on a new RPi 3, but it should be applicable for earlier models.
So you have your RPi and are "chomping at the bit" to start using it. Well before we start make sure you have the following items...
- A network to connect the RPi to (via Wi-Fi or wire)
- An HDMI monitor or TV
- A USB mouse
- A USB keyboard
- An 8GB or larger micro SD Card
- A Windows PC or Mac that can read micro SD Cards via a card reader or SD slot+adaptor
First you need to install a LINUX operating system on to the micro SD Card but before you do that format the card using the SD Card foundations Formatting tool, which you can download from here...
There is a version for Windows or Mac OSX and after downloading the tool of choice, extract and run the Setup program. Once installed, run the program with the micro SD plugged in to a card reader or SD card slot on the computer. It is good practice to give the card a volume name such as "Signal_K" which will remind you what is on the card at a later date as one LINUX distribution card looks much the same as another.
If you intend to use the Raspberry Pi for other things, not just Signal K, I would strongly recommend preparing one SD Card for the Signal K installation and have another SD Card with a normal Raspberry Pi installation and then you can keep things separate and clean.
Once your SD Card is properly formatted, we need to copy a LINUX Operating System on to it. To make things easy the nice people at RaspberryPi.org have created a "NOOBs" distribution which can be downloaded from here....
Select the NOOBs option on the left hand side (not the NOOBs Lite) and click on the "Download Zip" button. It is quite a large file approximately 1GB, so make sure you have a fast internet connection i.e. don't leave it till you get down on the boat !
Once downloaded open the ZIP file and extract all files/folders to your blank and freshly formatted micro SD Card. Once the copy operation is complete, insert the micro SD Card in to the RPi with the unit powered down. With all of the cables and peripherals plugged in, power up your Raspberry Pi and follow the instructions that appear on the screen. With the latest "Jessie" release the amount of options you need to select are significantly reduced and the whole operation should only take 10-15mins.
After everything has been configured you should be presented with the RPi Desktop and your LINUX operating system is installed and running, just waiting for you to install Signal K.
Installing Signal K
The RPi installation of Signal K can be broken down in to three distinct steps;
- Install the tools and libraries required to run the Signal K server (the dependencies)
- Install a Signal K Server to process the Signal K data; we will install the Java-Server
- Install the Web Apps (consumers) that can read Signal K data
Step 1 - Install the Dependencies
Raspbian the LINUX distribution for RPi is based on Debian which has a powerful installation tool called "apt-get", which we will use to install some of the dependencies and tools required. Before you use "apt-get" it is always recommended to update its index of repositories (websites that store LINUX software) and to do that use the following command...
$ sudo apt-get update
Now we will download three tools; curl, git and build-essential. These tools will allow us to download more software, clone the Signal K server and allow it to run, Install the three tools using the following command...
$ sudo apt-get install -y curl git build-essential oracle-java8-jdk
Verify that Oracle Java(TM) is the default on your system:
$ sudo update-alternatives --display java java - manual mode link currently points to /usr/lib/jvm/jdk-8-oracle-arm32-vfp-hflt/jre/bin/java ...
Raspbian Jessie - Lite image ships with openjdk 7 instead of the Oracle Java. The maintainer recommends the Oracle Java; Update the package alternatives database:
$ sudo update-alternatives --config java There are 2 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ 0 /usr/lib/jvm/java-7-openjdk-armhf/jre/bin/java 1063 auto mode 1 /usr/lib/jvm/java-7-openjdk-armhf/jre/bin/java 1063 manual mode * 2 /usr/lib/jvm/jdk-8-oracle-arm32-vfp-hflt/jre/bin/java 318 manual mode Press enter to keep the current choice[*], or type selection number:
Then we use curl to add the AdaFruit repository, followed by "apt-get" again to install Maven, a build installation tool for Java. At the same time we also install Node, which is not actually needed for the Signal K Java server, but which includes NPM which makes installing the consumer web apps easy.
$ curl -sLS https://apt.adafruit.com/add | sudo bash $ sudo apt-get install maven node
(Note: you may have to check that jdk8 is the default after installing Maven - use: $ sudo update-alternatives --config java)
Once this has completed you can check that Node.js is installed OK, by typing...
$ node -v
and you should see "v0.12.11" appear or whatever the latest version is.
Finally we need to install a Bonjour (mDNS) service for LINUX called Avahi, which allows Apps and other network devices to Discover the Signal K server. To do this we will use "apt-get" again ...
$ sudo apt-get install libnss-mdns avahi-utils
To check if Avahi is installed and working correctly enter the following command...
$ avahi-browse -a
This will search for and list all of the discoverable devices/services on your network. Use ctrl+c to stop the search.
Step 2 - Install Signal K Java Server
In this "How To" guide we are going to use the Signal K Java Server, but we also have a guide for the Node Server which is the other popular Signal K server.
A Signal K Server is the central hub of a Signal K system; reading and converting the boat's NMEA data (or Signal K data from a gateway), which it then stores and logs, before outputting the Signal K data to web apps (consumers) on the boat or sending it off the boat to other vessels or Cloud services.
To install the Java Server, we will first create a clone of all the Java Server source files that are on the GitHub repository by using the "git clone" command...
$ git clone https://github.com/SignalK/signalk-java.git
This will create a folder called "signalk-java" in the Home directory of your RPi. We need to switch in to this folder with the "cd" command, and then install and run the Java Server using Maven...
$ cd signalk-java $ mvn exec:java
Maven will now complete the installation and run the Java Server. You should see a similar terminal output to that shown below, note the port number for the Java Server web interface is 8080...
If you intend to use a web browser running on the Raspberry Pi to view the Java Servers popular Freeboard app, then the Epiphany browser that comes with Raspbian is not suitable as it does not display the chart data correctly and it is recommended to install IceWeasel (Firefox for RPi). To do this use apt-get to install the new browser...
$ sudo apt-get update $ sudo apt-get install iceweasel
Once installed, open the IceWeasel web browser on your RPi and type this URL in to the address bar "http://127.0.0.1:8080/". This directs the browser to the Java Server on the RPi (127.0.0.1 is your local Loopback address) and you should see the following screen...
Step 3 - Install Signal K Consumers
A "Consumer" of Signal K data is any web app, mobile device app or software program that can read and use Signal K data. It is hoped that the number of consumers will grow rapidly as more developers discover this open format and dream up new applications to make boating easier, more efficient or just more fun.
The Java Server has a very simple "one click" web installer for installing Freeboard its native application, as well as two other Apps; Instrument Panel and Sailgauge. For the purposes of this "How to" we will install Freeboard, which is easily done by clicking on the "Install" button below the blue "Freeboard SK" button...
Installation will take a minute or so depending upon the speed of your internet connection and once complete you will either see some errors or an "Installation Complete" message...
Now you can go back to the main index page and click on the blue "Freeboard SK" button to run the Freeboard App...
If you have managed to get to the end of this guide, you will now have a good understanding of what Signal K is all about and in particular the Java Server. We have been using the server's demo file (select it in Configuration menu), but Java Server can also read NMEA0183 data via an NMEA to USB adaptor cable, NMEA2000 data via a 3rd party NMEA2000 gateway or both NMEA0183 and NMEA2000 via the new iKommunicate gateway.