I recently bought a dsc radio (icom m402). I would like to hook this up to my existing network. My boat came with all raymarine products (6000) autohelm, gps,radar and other instruments. They seem to be connected in a network (NMEA?) togeather via two wires ie not twisted pair or coax. The radio has an RCA jack to hook up the gps and says it accepts NMEA0183 ver. 2.0. Can I just create a rca jack connector and hook it up to the wire network, or is their something else I should do to hook it up. Thanks
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Raymarine
As I recall, Raymarine uses their own propriatary protocall called "Seatalk" for data transmission between their own brand of instruments. You will probably have to use a seperate output from your GPS & have it's output be NMEA to talk to your VHF. Right now the marine industry is in a battle to get back to using standards. Supposedly there is an NMEA2000 in works, but many Mfgr's (like Raymarine) prefer to limit customer options. Anyone know more on this?
As I recall, Raymarine uses their own propriatary protocall called "Seatalk" for data transmission between their own brand of instruments. You will probably have to use a seperate output from your GPS & have it's output be NMEA to talk to your VHF. Right now the marine industry is in a battle to get back to using standards. Supposedly there is an NMEA2000 in works, but many Mfgr's (like Raymarine) prefer to limit customer options. Anyone know more on this?
sea talk is right
Yea it is seatalk. Real neet network protocal that is only used in real simple computers. One line is transmit/receive command and the other is data. The data is NMEA082 formatted BUT without the transmit/receive command line the seatalk network will never send the data. There is also some overhead data in the data stream that makes it unusable to your VHF. The next thing to look for is if one of your seatalk networked items has a straight NMEA output. The nature of the seatalk net is that one device talks and everybody else listens until the device talking says it is done. SO if something is requesting GPS data and the GPS is sending it EVERY device gets the data and just ignors it and passes it along to the next. My raymarine chartplotter has a seatalk and straight NMEA outputs and I got the VHF to think the Loran is a GPS. Bill Roosa
Yea it is seatalk. Real neet network protocal that is only used in real simple computers. One line is transmit/receive command and the other is data. The data is NMEA082 formatted BUT without the transmit/receive command line the seatalk network will never send the data. There is also some overhead data in the data stream that makes it unusable to your VHF. The next thing to look for is if one of your seatalk networked items has a straight NMEA output. The nature of the seatalk net is that one device talks and everybody else listens until the device talking says it is done. SO if something is requesting GPS data and the GPS is sending it EVERY device gets the data and just ignors it and passes it along to the next. My raymarine chartplotter has a seatalk and straight NMEA outputs and I got the VHF to think the Loran is a GPS. Bill Roosa
NMEA 0183
I have a 1996 Autohelm 6000 and it has an NMEA output port which should be able to send most, but not all, of the data on the Seatalk bus. Read your manual and, from memory, it tells how to make the connections. NMEA is a 'talker' and a 'listener' system so the data only travels on the bus in one direction. It only needs a twin core cable but it is best to use a screened lead to avoid picking up interference. (Not co-ax) The pilot also has an NMEA input port as well so make sure you get the right one. Sadly my output port failed several years ago so I can still drive the autopilot from the GPS but cannot use the output to display data on an ICS Navtex.
I have a 1996 Autohelm 6000 and it has an NMEA output port which should be able to send most, but not all, of the data on the Seatalk bus. Read your manual and, from memory, it tells how to make the connections. NMEA is a 'talker' and a 'listener' system so the data only travels on the bus in one direction. It only needs a twin core cable but it is best to use a screened lead to avoid picking up interference. (Not co-ax) The pilot also has an NMEA input port as well so make sure you get the right one. Sadly my output port failed several years ago so I can still drive the autopilot from the GPS but cannot use the output to display data on an ICS Navtex.
Your Raymarine instruments are, no doubt, connected using a Seatalk network, all high end Raymarine GPS units are also provided with NMEA outputs. You should have no problem sending basic GPS info (position, etc.) to your DSC radio. As I understand, the conversion of data from Seatalk occurs within the GPS instrument. Any SL or RL series GPS/Chartplotter provides the NMEA output that your radio will recognize. Check your manual for the correct cable type to minimize interference. I seem to recall this topic being discussed in the Raymarine site customer service database. This QA tool is available to all at the site. Good Luck!
Bill Roosa: Correction...
Bill, With all due respect, your description of the SeaTalk communication protocol is quite wrong. The following is a simplified description: SeaTalk uses three active conductors (plus shield), two are simply power (+12v and ground). All data is transmitted over the single signal wire (there is no send/receive line as you state) at more or less random times. All devices send data by dragging the signal line to ground (a "wired-or" configuration). Of course data "collisions" can occur when more than one device tries to talk at once - but each device listens to itself and if it detects interference from another device it waits a random (small) time and tries again. The nice thing about this is that you can have many "talkers" on the network, however the communication is rather slow at 4800 baud.
Bill, With all due respect, your description of the SeaTalk communication protocol is quite wrong. The following is a simplified description: SeaTalk uses three active conductors (plus shield), two are simply power (+12v and ground). All data is transmitted over the single signal wire (there is no send/receive line as you state) at more or less random times. All devices send data by dragging the signal line to ground (a "wired-or" configuration). Of course data "collisions" can occur when more than one device tries to talk at once - but each device listens to itself and if it detects interference from another device it waits a random (small) time and tries again. The nice thing about this is that you can have many "talkers" on the network, however the communication is rather slow at 4800 baud.
Question for Derek
Derek, You seem very knowledgeable about marine electronis. Out of curiosity: How does the 4800 baud rate of sea talk compare to NMEA? Allen Schweitzer s/v Falstaff C-30 Hull# 632
Derek, You seem very knowledgeable about marine electronis. Out of curiosity: How does the 4800 baud rate of sea talk compare to NMEA? Allen Schweitzer s/v Falstaff C-30 Hull# 632
NMEA data rate
Just running out the door for our Labor Day weekend cruise,
but standard NMEA is also 4800 baud. (Some devices allow operation at other rates) Note also that the true NMEA electrical spec is not the same as RS232 serial data - but almost invariably works on a computer serial port.
Just running out the door for our Labor Day weekend cruise,
but standard NMEA is also 4800 baud. (Some devices allow operation at other rates) Note also that the true NMEA electrical spec is not the same as RS232 serial data - but almost invariably works on a computer serial port.- Status