Friday, 23 January 2015

Too Many Networks - NMEA 2000, STng & More

Turck Devicenet Hub - For NMEA 2000
As you may have seen from our earlier story, we're progressively updating to newer navigation systems on board Crystal Blues, with our first update being the autopilot system. 

It is getting crazy folks - upgrading the systems in stages means that presently we have both the old and the new networks running, which means (count them) seven data networks on board :  NMEA0183 / NMEA2000 / ST1 / ST2 / STNg / HSB / Ethernet.

The NMEA 2000 networking standard is clearly the preferred network for the future, and fortunately has been adopted by our preferred vendor Raymarine, even if they insist on using non-standard connectors for their own version called STNg (those extra pins and wires in the Raymarine cables are there to carry legacy Seatalk 1 data). 

Our new autopilot uses only STNg, the older unit uses ST1.  Our sailing instruments use ST1 and ST2, plus NMEA0183.  And of course the older radar and sonar use Seatalk HSB to share graphics.  What a nightmare.  Unless we put a completely new system on board, we needed a way to integrate now,  provide a logical upgrade path in the future and to monitor what was happening on the network.

Too Many Networks - But They're All Talking Now 

First off, we ran a Raymarine STng data bus through the vessel, with spur points and sockets where they'll be needed in the future.  

At the Nav station this is tapped into an NMEA 2000 network that feeds data to the PC in the Nav station via an Actisense converter.  So the PC can now monitor ALL the network data on both the old and the new networks.

Two Pilots Are Better Than One

The NMEA 2000 network is really just a single Turck Device Net distribution board, purchased surplus on Ebay for less than thirty bucks (see the story on Panbo here).  Its pictured at the top of this story.  NMEA 2000 uses the Device Net physical and specification, just like many other industrial applications (including automotive networking).  It eventually will tie in to our Mastervolt power systems (regulator, charger and inverter) as well, so we'll have one integrated control network, we hope.  Right now, we can monitor all the old and new devices and all of the system data on the PC, using the Actisense monitoring software.

Our work so far has involved installing the new Raymarine Autopilot system, whilst retaining functionality on the older autopilot. We always cruise with two autopilots installed and operational - everything from the compass to the control head and even the rudder position indicator is all duplicated, and can be easily switch selected.

At this stage the planning has borne fruit, with the old and new systems chatting away quite happily.  At sea the integration worked fine, everything talking and listening as it should - we've sailed from Singapore to Langkawi and then on to Phuket without a glitch.

Our new radar, when installed, will eliminate the old HSB network connections, but will introduce yet another new network - Raymarine's version of Ethernet, called Seatalk HS. Seems we can't escape the network cable spaghetti just yet.