BR-355 NMEA-0383 Puck to ICOM M304

[allanpeda]

So I see that the ICOM M304 that I bought last year has two leads for "NMEA 0183 ver 2.0 or 3.01"

ICOM leads:



GlobalSat BR-355 leads:



Seems that if I can get NMEA to communicate wth the ICOM, and then it will be fully GMDSS functional. Okay, some might say cheap, others might say resourceful, but I see that the $50 Globalsat BR-355 GPS puck outputs NMEA-0183 v2.2 sentences at 4800,n,1. I assume, since the brochure says that the BR-355 can get voltage from USB, that Vcc is 5volts. So if I get 5 volts to the puck, connect black of the puck to green on the ICOM, and figure out a good voltage source of 5v (LM317 maybe) for the puck, I should be golden.

Anyone ever try this? Is this idea doomed to fail?

[goboatingnow]

They do a serial version that's just a different cable.that's the one you want. But your idea is fine. Is the serial data available on the USB version. Then you need a power supply, a simple series PDA regulator and a couple of capacitors will do the trick if you know what you're doing

Dave

[allanpeda]

Originally Posted by goboatingnow

They do a serial version that's just a different cable.that's the one you want. But your idea is fine. Is the serial data available on the USB version. Then you need a power supply, a simple series PDA regulator and a couple of capacitors will do the trick if you know what you're doing

Dave

The BR-355 is serial, not USB, sending text at 4800 bits/sec. Any serial version is simply the BR-355 connected to a DB-9 adapter, and a USB connector for power. The DB-9 is superfluous with the ICOM, as it's just wire leads on the VHF.

[hellosailor]

Allan, GPS "pucks" that use the PS/2 connector like yours does are common. Or were common. The important part for the interconnect is pins 4 & 5 on your diagram, the ones shown as RX and TX. You connect the RX from the GPS, to the TX on the radio. And you connect the TX on the GPS, to the RX on the radio.

RX to TX, TX to RX, because what one unit transmits, the other units needs to receive. If you get them crossed, or if the documentation is confusing (since RX and TX are relative to each device) just check all the software settings and then cross the two wires the other wire. (Twist 'em together, temporary, until you confirm the right way.)

Your pins 1 & 2 are the positive (VCC) and ground for the GPS power, and *usually* you can ignore using a common ground between the two devices, or you can *usually* wire the shield and ground all in common. Most of these GPSes expect no more than 5VDC on the power lines, putting 12v ship's power on the VCC connection may fry it. You'd need to check the specs to be sure for your device.

[s/v Jedi]

This equipment is not compatible because the GPS is single-ended serial (RS-232) and the VHF is RS-422.

Having said that, it'll prolly work if you connect GPX TX to VHF RX+ and GPS GND to VHF RX-

cheers,
Nick.

[goboatingnow]

Originally Posted by s/v Jedi

This equipment is not compatible because the GPS is single-ended serial (RS-232) and the VHF is RS-422.

Having said that, it'll prolly work if you connect GPX TX to VHF RX+ and GPS GND to VHF RX-

cheers,
Nick.

It will work fine. There no need for two way serial comms. Just gps tx to VHF rx. There's no handshake on nmea.

Dave

[allanpeda]

I am digesting this, looking at this essay and reconciling these recommendations.

Note: I have not bought the GPS yet. Is there a better one to look at? Perhaps one that hooks up directly to NMEA0183 with an RS422 balanced serial connection.

$25,000 question:
How would I test this?

[allanpeda]

See also

http://www.cruisersforum.com/forums/...2-a-12967.html

[s/v Jedi]

Originally Posted by goboatingnow

It will work fine. There no need for two way serial comms. Just gps tx to VHF rx. There's no handshake on nmea.

sounds awfully like what I wrote... except that there's 2 conductors labelled Rx on the VHF and only one labelled Tx on the GPS... hence I explained how to deal with that too

ciao!
Nick.

[allanpeda]

Since I have not bought anything yet, does anybody know of a GPS receiver for under $100 that outputs the correct RS422 balanced NMEA-0183 signal? I'd rather get the right hardware if it's just a matter of research up front.

[hellosailor]

Maybe this helps:
http://www.cruisersforum.com/forums/...2-a-12967.html

Bottom line is that RS422 is designed for higher speeds, longer distances, and higher noise immunity. The entire PC world used RS-232 while Apple used RS-422 and guess which one became the standard for inexpensive serial communications? Because it works, well enough and cheaper, for most consumer use.

I would expect a GPS with RS422 output to be a gold-plater designed for commercial and industrial applications, like feeding a signal from the stack on a cruise liner down five hundred feet of wiring to the computers.

[s/v Jedi]

Every Furuno GP-32 does RS-422. All my old Raytheon gear did RS-422. The only GPS I had that did RS-232 was an old Garmin.

ciao!
Nick.

[carlspackler]

See also this thread.