[POTM] dAISy - A Simple AIS Receiver

[chicken 630]

Hi Ross,

Yes, you can feed the serial data out of the HAT into an Arduino or ESP8266. It's 8N1 UART at 38400. You can expect a few hundred messages / minute in very busy areas down to a few per minute in quieter locations.

The AIS payload is encoded into !AIVDM messages. If you want to do more with the AIS data than just forwarding it, you will have to decode the !AIVDM message and then make sense of the binary AIS payload embedded in them. You can find detailed documentation of !AIVDM and payload structure that here.

As you can see, it's pretty exhaustive. If you want to process AIS messages on the Arduino/ESP8266, you likely will have to focus on a few message types. 1, 2, 3, 5, 18,19 are the most important for tracking ships. This here is an Arduino library for AIS decoding that I found, but I never used it so can't vouch for it.

Happy to share logs of real-world AIS data if that's helpful. If interested, send me a PM.

Regards,
Adrian

[Varnak 1]

Hi Adrian!
I tried to figure it out myself, but .... without your help it will not work.
Please, if you have time, answer a few questions.
I'm trying to run your project on si4463 (revision B1), but with 26Mhz quartz.
WDS 3.2.11.0 does not correctly open your WDS_si4463_revb1_direct_rx.xml.
I have the "Direct RX" mode, in the "RF parameters" tab there is no "Preamble pattern" item.
Tab "Packet" is completely absent.
In the "GPIO and FRR" tab, WDS 3.2.11.0 shows a complete absurdity (((...
Could you show how these things are tuned for you? Or prompt
Where can I find WDS 3.2.6.0?
Thank!
Sorry for the google translator.

[chicken 630]

Hi Varnak,

I just pushed a configuration file for WDS 3.2.11 that I had laying around. I haven't tested it, so not sure if it works as is.
https://github.com/astuder/dAISy/blob/master/WDS3211_si4362_revb1_direct_rx.xml

Best Regards,
Adrian

[chicken 630]

FYI: dAISy works in Direct RX mode. Unfortunately, the built-in packet handler of the radio IC does not work with AIS.

[Varnak 1]

Thank you very much! Can this configuration be applied to si4463? You wrote about si4463,
"Unfortunately two pins (GPIO2 and GPIO3) are reserved to control the RF
switch that connects the antenna with RX or TX channels. But after a
few minor changes to my code I had dAISy working.

Here's the branch on Github: https://github.com/astuder/dAISy/tree/E10-M4463D
The wiring changed:

GPIO0 -> P2.0

NIRQ -> P2.5

GPIO2, GPIO3 -> no longer connected to the LaunchPad"

Or I need for your "dAISy-E10-M4463D"
GPIO0 configure RX_DATA_CLK.
GPIO1 configure RX_DATA.
GPIO2 DONOTHIG.
GPIO3 DONOTHIG.
NIRQ configure CCA.
SDO DONOTHIG (or maybe SDO configure Output SPI serial data out? ).

Thank!

 

 

 

 

[Varnak 1]

Adrian you can show the settings for "GPIO and FRR" that you used in the dAISy-E10-M4463D project?

[chicken 630]

The Si4463 is backward compatible, as long as the chips have the same revision (B1 in this case).

The pin out depends on the breakout board that you use for your project. I don't have a screenshot as I never updated the dAISy-E10-M4463D project to the new version of WDS. dAISy requires CLK and DATA from the radio, which the 4362 config files map to GPIO2 and GPIO3. If necessary, move them to other pins as they are available on your breakout board.

But don't change CTS (GPIO1) as this pin is essential for SPI communication!

[Varnak 1]

It works))) Thanks Adrian! I do not have an AIS source, but I have a WAV file that I send from my HackRF and it works))

I get a lot of errors, but I think this is the subtlety of setting frequency, gain and other HackRF settings.
Again, sorry for the google translator.

[chicken 630]

Happy to hear that 🙂

Yeah, probably keep gain to a minimum. I would go with -50 dBm or less.

And no worries about Google Translate, it does a great job.

[Varnak 1]

Hi Adrian! I was in St. Petersburg, recorded the AIS broadcast and was surprised when I played it on the second frequency 162.025 at home ... it works too!))) But WDS is set to 161.975. Do you programmatically switch channels by RSSI level and after what time? If you can tell me where in the program it is. I'm not a programmer at all. Here's a video of how your dAISy looks at me))

[chicken 630]

Hi Varnak,

The dAISy software does change the channel every so often. The code for switching between the channels start at line 329 in packet_handler.c
https://github.com/astuder/dAISy/blob/master/packet_handler.c#L329

The receiver will switch to the other channel when the state is PH_RESET, which is the case after an error, successful message, or when there is no start of message within PH_SYNC_TIMEOUT (defined in line 27) clock ticks (one tick being 1/9600 second). Statistically, it will miss at least 50% of the message as it can only listen on one channel at a time.

Regards,
Adrian

[Chumikov 0]

On 11/2/2014 at 3:05 AM, chicken said:

Complete AIS protocol documentation can be found here: http://catb.org/gpsd/AIVDM.html

 

@@PaulTech my cheap hot air station saved my butt more than once, best investment ever.

 

In other news, as posted on other threads, I found a case for dAISy USB. It required redoing the board layout, but I really like the new form factor.

 

I also learned, that the LDO I use (MIC5205) does not like MLCCs as output capacitors. I had to go back to tantalum caps to get rid of a 200mVpp oscillation.

 

And I finally got a "real" AIS receiver off eBay. Turns out dAISy still has a long way to go to compete with these. But then, this particular model costs $450 new ($400 without GPS) and is about 7x the size (volume) of dAISy.

Hello! Thank you for your work! Tell me please, did you compare the circuitry of your receiver and receiver SR162? What are the main differences?

Thank!

[chicken 630]

Hi Chumikov,

The SR162 uses a Z80 MCU and two CMX589A GMSK modems (one per channel). The radio portion looks like a superheterodyne receiver with an oscillator, crystal filters and a ton of trimable passives. See attached a picture of the insides of the SR162.