The cool thing about this configuration is that:
- As many devices as you want can access the NMEA data
- The Raspberry PI only draws 700 mA
- When they're done using rthe NMEA data, devices (laptops, tablets...) can shutdown, the NMEA data will still be read and available whenever a device connects on the Raspberry Pi's network
We assume that you already have a Raspberry PI, along with its power supply (AC or DC, whatever).
We will show how to setup everything so the Raspberryt PI reads the NMEA data, and re-broadcasts them. As an example, we will show how to consume them from OpenCPN.
We will also need to edit several configuration files and other scripts. You can use any editor you wish, "nano" can do the job, I myself prefer "vi". At the end of the day, that's the same, only the result is important.
Requirements
First, flash the SD card, as explained here. I used the Raspbian image. Comes with Java.Next, we will require several softwares to be installed on the Raspberry PI, some are necessary, others are convenient.
An FTP server
This one will be very convenient when you will need to transfer files on you Raspberry PI.To install, type:
Prompt> sudo apt-get install vsftpd
Then edit (sudo edit) /etc/vsftpd.conf:
anonymouse_enable=NO
local_enable=YES
write_enable=YES
local_umask=022
chroot_local_user=YES
user_sub_token=$USER
local_root=/home/$USER/ftp
Start this ftp as a service on the PI:
Prompt> sudo service vsftpd restart
Install RXTX Java libraries
Read this good article.Just type:
Prompt> sudo apt-get install librxtx-java
We will see in the next section what to do with this.
Fing
A very cool utility. Combination of Find and Ping.
Prompt> wget http://www.overlooksoft.com/packages/download?plat=arm
Prompt> sudo dpkg -i overlook-fing-2.3.deb
Prompt> sudo apt-get install libpcap*
and finally:
Prompt> sudo fing
OlivSoft
You have just installed the libraries you need to use the serial ports (Serial or USB), now we need to modify the launching script to take that in account.Make sure you have the last version of the soft, up to date.
It is available on Google Code, in the download section.
The best way to do that is probably to install it on a box connected to the internet, and to let the software update itself.
Then you can transfer all the directory where it is installed (using FTP) on the Raspberry PI.
Once this is done, navigate to the
all-scripts directory, and edit the script named olivsoft.
You can add a line in the menu:
echo \| P for Weather Wizard, with http proxy
echo \| S for NMEA Sniffer
echo \| H for Headless NMEA Console
echo \| POL for Polar Tool
... and then the corresponding execution definition:
...
elif [ $choice = "H" ] || [ $choice = "h" ]
then
JAVA_OPTIONS="$JAVA_OPTIONS -Dverbose=false"
JAVA_OPTIONS="$JAVA_OPTIONS -Dheadless=yes"
JAVA_OPTIONS="$JAVA_OPTIONS -Dserial.port=/dev/ttyUSB0"
JAVA_OPTIONS="$JAVA_OPTIONS -Djava.library.path=/usr/lib/jni"
#
HEADLESS_OPTIONS="-output=HTTP:9999"
HEADLESS_OPTIONS="$HEADLESS_OPTIONS -output=TCP:7001"
# HEADLESS_OPTIONS="$HEADLESS_OPTIONS -output=FILE:.\logged-data\headless.nmea
java -client -Xms512m -Xmx1024m -classpath $CP $JAVA_OPTIONS olivsoftdesktop.OlivSoftDesktop $HEADLESS_OPTIONS
elif ...
Notice that /dev/ttyUSB0 is the USB port the GPS in connected on. In this case, the data will be re-broadcasted on TCP, port 7001, as well as on HTTP port 9999.
We will see below how to start the program.
Create an ad-hoc network, from the Raspberry PI
Read this good article.Make a backup:
Prompt> sudo cp /etc/network/interfaces /etc/network/interfaces_backup
Then edit (sudo edit) /etc/network/interfaces:
auto lo iface lo inet loopback iface eth0 inet dhcp auto wlan0 iface wlan0 inet static address 192.168.1.1 netmask 255.255.255.0 wireless-channel 1 wireless-essid RPiOnTheBoat wireless-mode ad-hocIn the lines above,
RPiOnTheBoat will be the name of your ad-hoc network.
Restart
wlan0 (wlan0 is the name of the wireless network interface).
Prompt> sudo ifdown wlan0
Prompt> sudo ifup wlan0
(reboot in case you have an error message)
Then we might need a DHCP Server:
Prompt> sudo apt-get update
Prompt> sudo apt-get install dhcp3-server
Then edit (sudo edit) /etc/dhcp/dhcpd.conf
ddns-update-style interim;
default-lease-time 600;
max-lease-time 7200;
authoritative;
log-facility local7;
subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.5 192.168.1.150;
}
Reboot..., all should be all set!
Let's if that's true.
Run it
Connect the things first:
Only the Wireless dongle is in
Plug the SD Card in (contains the OS)
Plug in the GPS
Connect the power supply
ssh.
Notice in the steps above, that there is no mouse, no keyboard, and no screen connected on the Raspberry PI. We could have done so. But we didn't.
To demonstarte the full compatibility of this scenario, we will do the subsequent operations from a Windows box.
Connect to the Raspberry PI's ad-hoc network
The wireless networks are usually available in the Windows taskbar. If not, open your Network Control Panel, you'll find it there.
RPiOnTheBoat), this is the one you defined.Then, we will use ssh (PuTTY) to start the re-broadcast:
olivsoft, and start the script olivsoft:
Prompt> ./olivsoft
To stop it:
Re-connect on the Raspberry PI with
ssh
Find the process, by typing:
Prompt> ps -ef | grep java
Then send it a SIGTERM signal:
Prompt> kill -SIGTERM 2493
Where 2493 is the process id. This way, the process will shut down nicely (by design, it understands that signal, which would be a Ctrl+C from the command line).
The process being up and running, define a network connection in OpenCPN:
Click Apply...
You can connect like this with as many devices as you want.
Voilà!
Next, we will try with the full NMEA station, with Pi4j. Then the HTML5 console will also be available, from http://192.168.1.1:9999/html5/console.html.
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