Seatalk option: SOG to STW. Request to Trip&Total log

[Seehund]

Hello,

My paddel wheel (speed transducer) in not connected to my tri-data Raymarine display. I'm using the SOG to STW inside seatalk options and is working great. Nmea3wifi receive the RMC sentence in P2 and generate the seatalk message, My tridata instrument display the speed and my wind instrument can calculate the real wind speed and angle.

But the trip log and total log is not working in the tridata instrumment. Would be possible for Nmea3wifi generate the seatalk S21, S22, S25 messages? Total log can be stored in the eprom of nmea3wifi so is not lost after re-start?

This is my request. Thank you very much in advance.

[dagnall]

Seehund.
(Updated and Edited version!)
The use of SOG to replace a STW paddle wheel data was primarily just to give Speed display on the instruments.
I am not sure that if we sent Trip log data on seatalk, if it would be displayed on the LOG instrument.
This would need to be checked before even thinking about adding an internal log..

The fact that the Raymarine then thinks it has STW and so the wind instrument then calculates "true" wind is a very complex issue! To calculate true wind really needs SOG and COG.. but the Raymarine does an approximation using just STW..
I am sure this will start some discussions!!

I will discuss the possibility of adding trip log data in a future update with Luis, but I am pretty certain that we would not want to store any navigation data in internal Eprom memory. (its rather full already)

Cheers
Dagnall

[Seehund]

Hi Dagnall,

Thanks for your reply and sorry for the delay, have been ot saling on summer holidays with not mutch intenet connection.

My boat have 2 units Raymaine tridata instruments. Before removing the paddlewheel one was configured as master (the one with the paddelwheel connection) and the second one was configure as slave (this one only had the seatalk connection). Both tridata did display the same total log and trip log.

So, I can confirm that Raymarine tridata will display total log and trip log if received on the seatalkbus. I can try a test firmware when available.

Also, the wind instruments are calculating right now true wind.

So, with trip log, nmea3wifi will works as multiplexer and as full paddlewheel simulator.

Another anoying thing is that for SOG to STW conversion can works I must send RMC on P1 or P2 input. My boat have a stalk gps that send RMC sentence on Seatalk. My Raymarine E80 plotter read seatalk RMC and convert to Nmea. Nmea3wif read this RMC nmea from plotter on P2 input and the conversion is working. But if I turn off the plotter lost the conversion.

Would be posible to take the RMC from seatalk when making the SOG to STW conversion?

Thanks for your help

[dagnall]

Hi Dagnall,
....
Would be posible to take the RMC from seatalk when making the SOG to STW conversion?

Sorry for my delay in responding.. I have been doing some other updates to the NMEA3 code, and had missed this suggestion!.

The SOG to STW feature is something we built into our "NMEA to Seatalk" conversion code. I can see that it might be helpful if the SOG to STW also accepted SOG from the seatalk databus.

This code (attached) should now make the Multiplexer send a "fake" STW (Datagram20) every time it sees a Datagram52 (GPS SOG). But please note that, just like the way this feature works with NMEA data, if the multiplexer sees any other Datagram20 sources, it will STOP sending the "fake" STW.

I have tested this in my network and noted that I made ST52 from both VTG and RMC once a second, so I saw TWO ST20 a second. I am not sure if this may result in display flickering.. or other undesirable issues. The way it works in your boat will therefore depend on EXACTLY which Seatalk datagrams your GPS (or plotter) is generating.

I have attached a zip with a test "NMEA3.ino.bin" that you can try.

Dagnall

[Seehund]

Hi Dagnall,

Thank you. Will test as soon as I can go again to the boat.

Wii report here my results.

Thanks again

[Seehund]

Hi Dagnall,

I have test your demo code and is working great.

Nmea3 wifi can now read SOG directly from the Seatalk GPS and generate the STW. Now my raymarine instruments are happy and display speed and true wind,

If in a future version you can add the trip seatalk command, nmea3wifi will be working as a full paddelwheel simulator.

Thanks again for your code