As an NMEA novice, I wondered if you experts could clarify something for me.....
All I have ever done with regard NMEA in the past is to connect my DSC VHF to my plotter for position polling. With the new boat, I am intending to revamp the nav equipment, as there is only a plotter/radar up on the flybridge and a 20 year old Autohelm Navcentre at the lower helm. There are depth/log repeaters up on the flybridge, and also autopilot control via a ST7001 controller upstairs and and ST5000 controller downstairs.
I know that NMEA0183 is the way the older equipment communicates, and I think I understand that this is done by the various instruments transmitting "sentences". If I've got this right, the "sentence" is actually a three character identification followed by a value. So, for example, a depth display would transmit the sentence for depth followed by the actual depth value. I assume therefore that the receiving equipment must listen out for the sentences that it can receive and ignore the rest? Does this therefore mean that the sentences are being sent continuously from the originating instrument, whether anything is listening to is or not?
I know this may all sound a bit basic, but I'm just trying to understand how the protocol works before I start ripping out wires