electronic decisions

[dvx216]

Just to be clear, N2K and 0183 have nothing in common, not even the communication formatting. NMEA 0183 is strictly serial communication, if you want to equate it to something then use RS232. You can hook up an RS232 terminal to any 0183 Tx line and see what it is transmitting. NMEA 2000 is completely different and at it's core may be compared to RS422, but that's a stretch. 0183 is not packetized like N2K is, N2K is more like ethernet network packets then anything else. Just using common terms here to describe this, I know they are vey different in practice.

0183 can use just two wires, they don't even need to be shielded to work. Should be when installed, but not needed. N2K CAN Bus cables are completely different in that they also carry power and the data lines need to be balanced like RS422 does. Drop wire (4C) is usually used to for power, not for singling wire. Unless your thinking of cat5/6 network wire.

Now if your referring to "signaling wire" then that is different. Mass transit uses a lot of that stuff and it's very heavy gauge wire compared to the 22/24 ga wire used in communications.

So does 0183 not use a binary signal much like nm2k or is 0183 a analog signal . I'm under the understanding that is why the industry went to this type of communication system to get away from impedance interference.

 

[Skybolt]

So does 0183 not use a binary signal much like nm2k or is 0183 a analog signal . I'm under the understanding that is why the industry went to this type of communication system to get away from impedance interference.

NMEA 0183 is a a serial communication with a very simple protocol. It cannot be routed or use switches. But it can use serial multiplexers, but they are a function of hardware that has nothing to do with 0183 itself. The impedance you are referring to is known as a differential signal and is what ethernet is based on. RS232 is a voltage based signal. RS422 is more like a differential signal, the lines needs to be balanced to 60 ohms and impedance matched with terminators that have the 60 ohm resistor and capacitor in them.

What you are calling a "binary" is known as digital communication(s). 0183 and N2K both have digital protocol they use, although have nothing in common except that they are digital. RS232 can be analog in that it can have a wide range of voltages used to communicate based on hardware. Originally RS232 was +/- 15v, somewhere in the late 80's early 90's it turned into 0-5v a completely digital signal. When used in NMEA communications it is 0-12v.

NMEA 0183 is basically used for NAV data only, it doesn't have more parameters then that. Some custom protocols have been used and are proprietary to the manufacturer. NMEA 2000 has a wide range or packets known as PGN's that support just about anything on a boat. Way past NAV data, it includes engine, environment data and can even control lighting and audio. And again, the protocols are completely different.

 

[dvx216]

NMEA 0183 is a a serial communication with a very simple protocol. It cannot be routed or use switches. But it can use serial multiplexers, but they are a function of hardware that has nothing to do with 0183 itself. The impedance you are referring to is known as a differential signal and is what ethernet is based on. RS232 is a voltage based signal. RS422 is more like a differential signal, the lines needs to be balanced to 60 ohms and impedance matched with terminators that have the 60 ohm resistor and capacitor in them.

What you are calling a "binary" is known as digital communication(s). 0183 and N2K both have digital protocol they use, although have nothing in common except that they are digital. RS232 can be analog in that it can have a wide range of voltages used to communicate based on hardware. Originally RS232 was +/- 15v, somewhere in the late 80's early 90's it turned into 0-5v a completely digital signal. When used in NMEA communications it is 0-12v.

NMEA 0183 is basically used for NAV data only, it doesn't have more parameters then that. Some custom protocols have been used and are proprietary to the manufacturer. NMEA 2000 has a wide range or packets known as PGN's that support just about anything on a boat. Way past NAV data, it includes engine, environment data and can even control lighting and audio. And again, the protocols are completely different.

Okay so the binary signal is what they were shooting for originally to get away from analog signal being affected by surrounding emfs which would be degrade or corrupt the signal. Is this why shielding was so important back in the day with communication systems. And not so much now .

 

[Skybolt]

... Is this why shielding was so important back in the day with communication systems. And not so much now .

Shielding is still very important, cat6 plenum rated cable even has a plastic separator to prevent cross talk in the pairs because of the data rate. Shielding is still very important, probably more then ever because of the speeds that are achieved.

 

[dvx216]

Is the shielding opened ended or connected to a ground source at both ends on short runs in a boat. Is a M12 connector suitable for nm2k.

 

[unsalted]

Is the shielding opened ended or connected to a ground source at both ends on short runs in a boat. Is a M12 connector suitable for nm2k.

I’m back to the article I posted earlier about re-terminating N2K cables using Maretron FA-CM-ST and FA-CF-ST connectors. I see others have these as well (noticed a Garmin version in my searches). The question is whether the existing cabling is N2K, or good enough. The N2K is a broadcast bus much like the early coaxial Ethernet technology. The bus is a coupled, but continuous length of cable, with terminators on either end and drop points for devices. If you disrupt this bus then you run the risk of disrupting all the devices on the bus, not just the single drop for your transducer.

 

[dvx216]

I’m back to the article I posted earlier about re-terminating N2K cables using Maretron FA-CM-ST and FA-CF-ST connectors. I see others have these as well (noticed a Garmin version in my searches). The question is whether the existing cabling is N2K, or good enough. The N2K is a broadcast bus much like the early coaxial Ethernet technology. The bus is a coupled, but continuous length of cable, with terminators on either end and drop points for devices. If you disrupt this bus then you run the risk of disrupting all the devices on the bus, not just the single drop for your transducer.

So my question is using the existing shielded wire and using M12 connector which is what Nm2k use suitable.