AIS reciever for Raspberry Pi, 2 channel

Updated 2024-01-20 !! OK with Bookworm !!

This post covers the setup for a AIS, dual channel, receiver for Raspberry Pi(RPi) with systemd autostart.

I'm using the RTL-SDR dongle V3 with almost zero temperature drift or the even better NooElec NESDR Nano 3

AIS posts with charts/maps

• OpenSeaMap and dispatcher 
• OpenStreetMap and dispatcher

Improve receiving range? Calibrate ! Instructions in this post

The best AIS application ? is found here !

Intro

The actual AIS software is RTL-AIS which connects to the dongle and outputs NMEA0183(N1) VDM sentences. The setup is used in the NMEA WiFi project.

If You want to start with a fresh Raspberry installation here is a post using Mac/PC/Linux.

The fantastic OpenPlotter(OP) project with guys Sailoog/e-sailing have done a package which is very easy to use. I really recommend the OP method, Installation A, compared with installing from source. (If You are using OP use the app "SDR VHF" instead)

Warning !

I'm using this setup on our boat and are using a simple buck converter, 12V DC => 5V DC, to source the Raspberry Pi 4. In this case the converter was placed direct below the SDR and interfered so much that there was almost no reception. So check for a good power supply, away from the dongle, and shielding.

Another trix to minimize the problem is using an USB extension cable so the dongle is away from the interferences emitted by the power supply and the computer.

As a last measure I added a ferrite bead on the USB cable which also increased the reception range.

Installation

Update OS

You must update cause there are bugs in older firmware. Open a terminal window/ssh and start with an update of the OS and firmware

$ sudo apt update && sudo apt full-upgrade -y && sudo apt clean

Installation A, from Openplotter package
If you are running this variant of software and get an error "Segmentation fault" you must use the other, B, method!!

Start  with dependencies for RTL-AIS

$ sudo apt install librtlsdr-dev libpthread-stubs0-dev

Choose a package file for Your OS. For RPi "standard" 32 bit download 

$ wget https://launchpad.net/~sailoog/+archive/ubuntu/openplotter/+files/rtl-ais_0.4.2-stable_armhf.deb

and install

$ sudo dpkg -i rtl-ais_0.4.2-stable_armhf.deb

If running RPi 64 bit

$ wget https://launchpad.net/~sailoog/+archive/ubuntu/openplotter/+files/rtl-ais_0.4.2-stable_arm64.deb

and install 

$ sudo dpkg -i rtl-ais_0.4.2-stable_arm64.deb

continue below with "Testing"

Installation B, from source

Start with dependencies for RTL-AIS

$ sudo apt install librtlsdr-dev

With GIT
If You don't have the GIT package install it with

$ sudo apt install git

Clone RTL-AIS from github

$ git clone https://github.com/dgiardini/rtl-ais

Without GIT
$ wget https://github.com/dgiardini/rtl-ais/archive/master.zip
$ unzip master.zip && mv rtl-ais-master rtl-ais

Then go to the created directory and compile

$ cd rtl-ais

Please note that there are a bug in Buster ! Check at Buster below

$ make

Copy the program to the right place. 

$ sudo cp rtl_ais /usr/bin

Testing
Connect the dongle to the RPi, and an antenna to the dongle, and start the software with 

$ sudo rtl_ais -R on -n

and something like this will appear with the VDM sentences at the end

Edge tuning disabled.
DC filter enabled.
RTL AGC enabled.
Internal AIS decoder enabled.
Buffer size: 163.84 mS
Downsample factor: 64
Low pass: 25000 Hz
Output: 48000 Hz
Found 1 device(s):
  0:  NooElec, NESDR Nano 3, SN: XXXXXX

Using device 0: Generic RTL2832U OEM
Detached kernel driver
Found Rafael Micro R820T tuner
Log NMEA sentences to console ON
AIS data will be sent to 127.0.0.1 port 10110
Tuner gain set to automatic.
RTL AGC mode ON
Tuned to 162000000 Hz.
Sampling at 1600000 S/s.
Allocating 12 zero-copy buffers
!AIVDM,1,1,,B,137KW60018PqU<bP6M2<?9iV08N=,0*7E
!AIVDM,1,1,,A,15V3Qh000I0qPQ8P7al=9bAf08Qf,0*6B
!AIVDM,1,1,,A,137KW60018PqU5DP6MQ<?ah00D1;,0*0B
!AIVDM,1,1,,B,137KW60018PqTtFP6N6t?IhF086b,0*1A

Exit with Ctrl+C

As You see the N1 data is available as UDP data at port 10110

Clean up with rm -rf /home/pi/rtl-ais/ /home/pi/master.zip

Autostart with systemd
Autostart with systemd will make the rtl-ais software start at boot and restart if it fails.
Create a file with

$ sudo nano /etc/systemd/system/ais.service

and add the following configuration

[Unit]

Description=AIS
After=syslog.target network-online.target

[Service]
Type=simple
User=root
ExecStart=/usr/bin/rtl_ais -R on -n
Restart=on-failure
RestartSec=10
KillMode=process

[Install]
WantedBy=multi-user.target

(If you don't want to log the NMEA sentences remove the "-n" from the "ExecStart" line above)

And then the following commands to get it up and running

$ sudo systemctl daemon-reload

$ sudo systemctl enable ais

Created symlink /etc/systemd/system/multi-user.target.wants/ais.service → /etc/systemd/system/ais.service.

$ sudo systemctl start ais

Check with the following command 

$ sudo systemctl status ais

You will get something like this if You succeed 

● ais.service - AIS

   Loaded: loaded (/etc/systemd/system/ais.service; enabled; vendor preset: enabled)

   Active: active (running) since Tue 2018-06-26 11:05:10 CEST; 41s ago

 Main PID: 1648 (rtl_ais)

   CGroup: /system.slice/ais.service

           └─1648 /home/pi/rtl-ais/rtl_ais -p 0 -R on -n

Jun 26 11:05:22 Zest rtl_ais[1648]: !AIVDM,1,1,,A,14`a0?001dPqOmHP6io<K9td08=9,0*01

Jun 26 11:05:28 Zest rtl_ais[1648]: !AIVDM,1,1,,A,B3uK=1P0=h>H22`1l69VSweUkP06,0*6B

Jun 26 11:05:28 Zest rtl_ais[1648]: !AIVDM,1,1,,A,13A4g<00000qhP4P3vLLS84p08@e,0*50

Jun 26 11:05:31 Zest rtl_ais[1648]: !AIVDM,1,1,,B,14`a0?001ePqOd0P6ja<K9tv058D,0*18
Jun 26 11:05:32 Zest rtl_ais[1648]: !AIVDM,1,1,,B,402R3a447wP000r;6vP4fwG00l4;,0*6B

If You have problems and would like to clean up, use the following commands 

$ sudo systemctl stop ais && sudo systemctl disable ais

and then delete the ”ais.service” file.

SignalK(SK)

If You are using SK and want to receive the N1 data? In the admin GUI go to ”Server => Data Providers”  and add 

• Input type: NMEA0183
• ID: AIS
• NMEA 0183 Source: UDP
• Port: 10110

Restart SK and check.

OpenCPN/OpenPlotter

Connection for OpenCPN

• Click the Options-icon
• Connections-tab
• Add Connection
• Network
• Protocol: UDP
• Address: IP address of workstation (localhost)
• DataPort: 10110
• Check “Show NMEA Debug Window” to see incoming messages.

Remarks

Inspiration to this setup has come from several places but this blog and this site gave the best information.

Many thanks to "dgiardini" who is maintaining the software and helped me with the Buster fix.

Buster

Because of a bug You have to edit the "Makefile", with "nano Makefile", and  the line in the beginning
LDFLAGS+=$(shell pkg-config --libs librtlsdr)

or 

LDFLAGS+=-lpthread -lm  -L /usr/lib/arm-linux-gnueabihf/ 

should be changed to

LDFLAGS+=-lpthread -lm -lrtlsdr -L /usr/lib/arm-linux-gnueabihf/

Note !!

If You did a "make" before the change of the Makefile do a "make clean" and then "make" again.