Problem connecting àis to laptop

[pir8ped]

On my own boat I have àis connected to my laptop and it works fine. Problem is, I can't remember how I set it up. I know the only connection to the laptop is a usb.

So I'm cruising on a friend's boat and he has an icom àis with a little screen which I find not very handy compared to seeing àis in opencpn. His àis has a serial plug with bare wires coming out. I connected a pair that the manual tells me are nmea+ and-, and connected them to the pair of wires that carry the data in a usb lead.

The laptop sees the connection but I get a message telling me that the device descriptor request failed (error 43)

Can I connect things this way? I seem to remember a serial to usb adaptor in my own slightly more complex setup. I hope it's feasible. We're moored far away from shops.

Thanks,

John

[montigre]

Might this help? AIS USB Installation

[barnakiel]

Connecting a serial data (rs232 or rs422 (I think your ICOM has 422, if what you wrote is 100% correct)) to a plain usb data carrying wires will not do.

You want a RS serial to USB serial cable = a cable that contains a chipset that converts the data according to required electrical settings at each end.

Unless your PC has the older DB-9 port (non USB, old, only older machines).

There are many types of RS to USB cables. Yours sounds like a RS422 to USB serial data cable. About USD10 in a local tinkerers' shop.

So this may be your flow:

1) make sure which RS standard is your ICOM (4 wires data is 422, 3 wires data with GND common is 232), (instruction manual ICOM)

RS422 (cabling is nmea in+, nmea in-, nmea out +, nmea out -),
RS232 (cabling is Rx, Tx, GND),

2) get relevant RS (232 or 422) serial to USB serial data cable,

3) get drivers onto the receiving PC,

4) set correct baud rates on the system / PC / plotter software,

5) plug and pray.

The data rate is baud 38400 because you are with an ais equipment. Set this rate in your plotter/PC software/system accordingly.

Cheers,
b.

[pir8ped]

That sounds a bit familiar b, thanks very much.

We'll have to wait for access to a computer shop. It's all sheep, foxes and ravens round here.

Thanks a lot,

John

[pir8ped]

I've pedalled 10 miles down the road (in the rain!) and bought a rs232 to usb cable.

One complication I forgot to mention is that the serial plug plugged into the back of the ais ends in bare wires. A couple of the wires are connected to the DSC VHF, and that's working fine as it is. So I have the rest of the bare wires to play with.

Back at the boat, I've realised I've made a mistake. I should have bought a rs422.

The ICOM manual refers to the names of the wires as nmea out -ve, nmea out +ve, nmea in -ve, nmea in +ve.

Rs232 needs gnd, receive and transmit.

Have I wasted my time and money? Is there any way I can connect some wires from the ais to the serial plug (of the serial to usb cable)? The laptop is just a listener after all.

Gnd to pin 5
Nmea out +ve to pin 2
Nmea out -ve to pin 3

I'm guessing....

Or do I have to go pedalling again and buy an rs422 serial to usb adaptor?

Thanks,

John

[wayne.b]

Originally Posted by pir8ped

Or do I have to go pedalling again and buy an rs422 serial to usb adaptor?

===

This is what I use:

FTDI - USB-RS232-WE-1800-BT_3.3 - 1.8M USB-A PLUG, STRIPPED WIRE END 3.3V 24AWG 6 COND. USB-RS232 CABLE, ASSEMBLY - Allied Electronics

[Pizzazz]

Typically, you would connect the negatives to ground and connect out +ve to pin 2 and in +ve to pin 3. Basically, rs422 works on differential voltages around a bias point, so when you ground it, sometimes you can trick the receiver to get it. Not ideal but works 90% of the time.

Note that serial port data wires have high DC impedance, so you can mix than as you please. Once you get tired of following logic, experiment with all combinations... You may stumble on the right outcome sooner.


You may have to disconnect the DSC.

[pir8ped]

Hey pizzazz,

Thanks for that. I did exactly as you suggested, and I can see the ais signals from other boats in opencpn.

However, 'own ship' is usually grey, occasionally switching to red.

The only nmea sentences I see in the debug window are AIVDM.

I guess I could use usb GPS mouse I have to supply the GPS info, but I expect that should be obtainable from the ais, which would be neater.

[pir8ped]

Job done. GPS info from GPS usb source, but hey, good enough. Don't want to disconnect the DSC..

Thanks for all the advice folks.

John

[sailersteve]

Milltech Marine has a nema 0183 USB AIS decoder type cable for my Standerd Horizin GS2200
for like 35 bucks . They also now have a wireless type thing of that for Ipad / Iphone.