dAISy Open Source AIS Receiver

[astuder]

With the help of muttnik, I came up with the following udev rule that starts or restarts Kplex when dAISy is plugged into USB:

SUBSYSTEM=="usb", ATTRS{idVendor}=="16d0", ATTRS{idProduct}=="0b03", SYMLINK+="ais%n", RUN+="/etc/init.d/kplex restart"

Put this rule into a file in the /etc/udev/rules.d folder. For example by using

sudo nano /etc/udev/rules.d/kplex-daisy.rules

You may need to reboot the Raspberry Pi after creating or editing this file.

[pcmm]

Might be a stupid question, but can you access the NMEA data and USB data at the same time? I see on the picture of the NMEA add-on that it states to not plug in the USB while connected to external power. I assume this is because the unit can take power from either source. If so can you "clip" the power connections on the USB side and still get the data?

[astuder]

Not a stupid question at all.

There are two reasons for the warning:

1. USB and NMEA side are not isolated. Powering from both sides at the same time may work but could cause ground loops and other fun stuff.
2. Because the NMEA add-on came much later, the dAISy main board has no measures to prevent back-powering the USB host. If the USB voltage drops below approx. 4.8V, current will flow from dAISy to the USB host which may or may not cause bad things to happen.

The preferred approach when requiring USB data and NMEA output is to only power dAISy from the USB side.

Using a USB cable with cut 5V wire could work. My main concern would be whether the USB enumeration sequence works in that setup. If the USB device is detected you're fine.

An alternative approach is to disconnect the 5V wire (red) between dAISy and the NMEA adapter. That way NMEA output and dAISy are powered independently. Of course that's only viable if the USB side is always powered.

[solosail]

I don't know much about RF... I just got the dASIy unit and I'm dying to try it out. Will a small VHF rubber ducky antenna work for testing. I'm guessing it would be low gain and thus short range... But it should work I think?
Any comments...
Thanks for any information!

[astuder]

A VHF rubber ducky will work fine if there are any ships nearby.

[prof_mariner]

Wow, this project is very impressive! I'll be watching this thread...

[Tenedos]

Probably time to jump in to share my experiences with dAISy. Adrian was kind enough to get a dAISy HAT to me for some testing and experimentation. I have been playing with it and it is pretty slick!

Note that there are two dAISy'ies. One is a standalone version that plugins in using a USB connector. The other is a HAT for Raspberry Pi, that you insert onto the Raspberry Pi GPIO pins. Obviously, HAT is designed only for the Pi (even though there are instructions on how to power it separately). If you intend to use it with a Raspberry Pi, the HAT version is convenient. That is the one I played with.

All in all, as I said, I think it is a pretty slick amazing little device. It took less than 10 minutes to get it running (you may need to do some configuration changes to disable console and re-configure Bluetooth (Raspberry Pi 3 only) but it is very straight-forward and takes a few minutes at the most).

Connecting it to my masthead VHF antenna, it simply worked and I started receiving vessel locations in San Francisco Bay. If you want to see the results yourself, you can check the AISHub San Francisco station 2404 Map, this is running on the dAISy HAT right now.

Since it conveniently sits on a Raspberry Pi, it is very easy to turn into a wireless AIS as well, to access from your phone, tablet etc using iNavX, the Signal K app I had developed earlier or any other app. You can integrate into an NMEA and/or Signal K network fairly easily. I had written a how-to guide to create a wireless AIS and dAISy simply works neatly on a Raspberry Pi, serving as a 'wireless AIS'.

We were discussing if the range could be further extended, which sounds possible. But for a $60 device, what comes is pretty amazing. From where I sit, it covers a 15nm radius with a mast head antenna. Combining it with a Raspberry Pi, you can have a fully functioning onboard computer, wireless AIS receiver, multiplexer (with kplex) etc for about $100, something hard to beat. And on top of everything, it is open source. Hats off.

[astuder]

I'm not sure if Mattkab is still active on this forum, but I wanted to point out his latest blog post. It's an easy to follow recipe to setup an inexpensive chartplotter with OpenCPN, a Raspberry Pi 3 and the dAISy HAT AIS Receiver.

https://mvcesc.wordpress.com/2017/04...aspberry-pi-3/

[astuder]

I released a new firmware update for the single-channel dAISy:
https://github.com/astuder/dAISy/tree/master/Firmware

This update is of special interest because it overcomes some of the handicap that is inherent to single-channel AIS receivers. Traditionally, single-channel receivers periodically alternate between the two AIS channels and therefore miss about 50% of the available AIS messages. For this reason, single-channel receivers take longer to pick up new AIS targets and are slower at updating positions of known targets.

With the new firmware, dAISy is able to capture a significant number of previously missed messages by predicting on which channel to expect the next message. This works best in areas with less AIS traffic due to statistics (lower probability of messages sent on both channels at the same time). In the worst case scenario of fully saturated channels (2250 messages per channel per minute), it will still miss 50% of the available messages. In my real world tests around Seattle (~300 AIS messages per channel per minute), the new smart hopping algorithm receives about 40-60% more messages than traditional channel hopping.

The firmware update is available for all single-channel dAISy AIS receivers produced since June 2015. Send me a private message if you have any trouble with the upgrade or would prefer if I perform the upgrade for you.

[rgleason]

Adrian has updated his website and line of AIS products.

So we've updated his AIS section in Supplemental Hardware


PS: Adrian, did you see the example of two land AIS stations sharing data using OpenCPN, I guess for redundency and expanded area, eand then reported to their own AIS servers, MarineTraffic, etc. ?

I'd like to find that description, discussion.

[TheOffice]

Originally Posted by pcmm

Might be a stupid question, but can you access the NMEA data and USB data at the same time? I see on the picture of the NMEA add-on that it states to not plug in the USB while connected to external power. I assume this is because the unit can take power from either source. If so can you "clip" the power connections on the USB side and still get the data?

I have the USB powering my unit and the NMEA in and out connected to my plotter. Works great!

[astuder]

Originally Posted by rgleason

Adrian has updated his website and line of AIS products.

So we've updated his AIS section in Supplemental Hardware

Thanks!

PS: Adrian, did you see the example of two land AIS stations sharing data using OpenCPN, I guess for redundency and expanded area, eand then reported to their own AIS servers, MarineTraffic, etc. ?

I'd like to find that description, discussion.

Are you talking about some kind of virtual station that creates one AIS stream for a larger area? I know of government services like in Norway, or repeaters like for example along the Columbia River.

I heard of a few people doing something similar on a small scale, mostly built around a network of Raspberry Pi's. But I don't know if they are using OpenCPN to do the data collection and forwarding.

[petter5]

I use two AIS receivers to expand the covered area - one connected over intenet and the other connected to a RPI locale for feeding extended AIS to my local opencpn.

Originally Posted by astuder

Thanks!

Are you talking about some kind of virtual station that creates one AIS stream for a larger area? I know of government services like in Norway, or repeaters like for example along the Columbia River.

I heard of a few people doing something similar on a small scale, mostly built around a network of Raspberry Pi's. But I don't know if they are using OpenCPN to do the data collection and forwarding.

[pcmm]

As an aside, I wonder why do all these AIS devices are using BNC or SMA connectors? they're such odd ball connections for this purpose. It means that to connect your VHF antenna you need to go searching for adapters for convert standard UHF connectors to these ones? Why?

[transmitterdan]

Originally Posted by pcmm

As an aside, I wonder why do all these AIS devices are using BNC or SMA connectors? they're such odd ball connections for this purpose. It means that to connect your VHF antenna you need to go searching for adapters for convert standard UHF connectors to these ones? Why?

Because UHF connector is too big. Also, almost no printed circuit mount UHF connectors are available these days. But the main reason is size. It requires the AIS box to be excessively large. So small low cost receivers don’t use UHF connectors.