NMEA output

MarkJohnson

MarkJohnson

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I am wanting to record electronically water depth from an echo sounder.

The sounder has NMEA output, and I have Psion's and PDA's that might be able to record the data.

Psions have RS232 port, and I have the serial cable.

Any ideas on how to make the electronic connection?

Regards

Mark J

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You can normally connect the NMEA out directly to the RS232 port. Wire up a connector connecting NMEA -ve to RS232 signal ground, and NMEA +ve to RS232 data in and off you go.

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On a serial port(9pin D connector) the connections are pins 2, 3 and 5.
Pin 2 is RS232 in (RX) pin 3 RS232 out (TX) I think, from memory.
Pin 5 is ground or NMEA neg.

If you are just looking to Rx NMEA then wire across pins 2 and 5.
If it doesnt work first time then try pins 3 and 5.

Try it with an emulator like Hyperterminal (accesories Windows).
The setup for NMEA V 1.5 upwards is:
4800, 8 N 1.

Hope this helps

Steve.


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I just checked my documentation on EIA standards and the RS232C 25 pin connector should be wired as follows:
Pin 1 Protective ground
Pin 2 Tx Data
Pin 3 Rx Data
Pin 7 Signal Ground

So, you should be using Pin 7 for the NMEA negative and Pin 2 for the NMEA positive (data).

The rest of the pin-out should not be of interest to you (but if you want it I can send it to you). I was once on a course where RS232 was described as "the most non-standard standard in the world" !!!!
I think on 9 pin connectors the pin-out should be the same as above, but it can depend on the manufacturer of the equipment not always following the standard.

Alan.
Nettuno, Italy.

<hr width=100% size=1>Alan Cloke
 
On the 9 pin D-Type, pins 2 and 3 are the opposite of the 25 pin i.e. on the 9 pin, pin 3 is TX and pin 2 is RX

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Extract from <A target="_blank" HREF=http://vancouver-webpages.com/peter/index.html> Peter Bennett's site </A>

<pre> The standard RS-232 connector is a 25 conductor DB-25, although
many PCs (and some other equipment) now use a 9 pin DE-9 (often
incorrectly called DB-9)

Serial Port Connections
Computer (DTE) Modem
DB-25 DE-9 Signal Direction DB-25
2 3 Tx Data -> 2
3 2 Rx Data <- 3
4 7 Request to send -> 4
5 8 Clear to send <- 5
6 6 Data Set Ready <- 6
7 5 signal ground 7
8 1 Data CarrierDetect <- 8
20 4 Data Terminal Ready -> 20
22 9 Ring Indicator <- 22

For NMEA-0183 interfacing, we are only concerned with Rx Data,
signal ground (and possibly Tx Data, if we want the computer to
talk to the GPS)

NMEA-0183 data is sent at 4800 baud.</pre>



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And now you need to pay $250 to www.nmea.org to get an explanation of all the gibberish that comes down the wire! The RYA must have done a deal 'cos their chart program turns gps nmea data into little dots on a chart!

Geoff

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Re: NMEA output - see wiring diagram at NavStation

There is an overview complete with wiring diagram for this under one of the FAQ at NavStation which also provides software for linking a PDA to your GPS and marine instruments to provide a passage planner, chart plotter and ships logbook (automatically linked to your instruments). This website also discusses using nmea multiplexers to link the output from multiple devices and also linking to the PDA using wireless bluetooth (even if your gps is not bluetooth enabled).
 
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