Raymarine Evo AP and OpenCPN

[jeroenimo]

Today I installed an Actisense NGW-1-ISO on board my parents boat, so the AP and OCPN can talk.
So I connected the NGW-1 to the listener and talker on the miniplex-lite and the other side to the STng backbone.
After some fiddling with NMEA sentences being echo'ed to the miniplex-lite talker ($GPGLL,$GPRMC,$ECAPB,$ECXTE) I got SOG,TIME,POS and COG visible on the p70 display of the AP, seems all to work well.
Now when I select a route and activate "track mode" it it successfully "locks on" and starts to follow in track mode. But then SOG disappears from the p70 briefly or a little longer causing the p70 to complain about no speed data input. Hence the AP stops following the track. Also the AP seems to be sluggish in finding the track.

Hardware

-Raymarine p70, EV-1, ACU400
-Nav PC (win7)with OCPN -> USB connected multiplexer with virtual com port
-Furuno GP33 (fake ONWA) -> NMEA0183 to multiplexer
-Oceansat Class B AIS -> NMEA0183 to multiplexer
-Actisense NMEA2000-NMEA0183 bridge connected to STng and NMEA0183 multiplexer

Possible problem/solution:

OpenCPN sends at 57600 baud the sentences to the multiplexer which sends it @ 4800 to the NGW-1. But when there is no flow control on the port sentences gets lost sometimes. 128 bytes is not a lot of buffer on the multiplexer.
OpenCPN has no flow control settings on it's com port but the Windows COM port settings do have Xon/Xoff and Hardware, I'll try if that helps.

Other solution: Bypass the NMEA talker from Multiplexer with USB serial, but I'd like to avoid that.

Next week I'll test if this makes the difference, but if anybody has an idea I'm open for more info!

[jeroenimo]

So, the issue was that the Shipmodul multiplexer-lite has 120 bytes buffer in which it should store the RMC and APB sentences before it gets send to the NGW-1, this is not enough, therefor there will be sentences discarded as they are well over 130 bytes sometimes. This off course causing erratic behaviour on the AP. A solution would be Harware flow control, but OpenCPN has no such settings in it's connection, therefor ignoring the settings of the com port.
The developer of the ShipModul Miniplexer has generously helped me and recognised the issue right away. The Miniplex lite has this issue and he has send me a replacement Minplex-3USB-N2K therefor eliminating the issue, now the multiplexer is directly connected to the Seattle-NG backbone and has enough bandwidth and buffer to send all it needs to send.
Big kudos to Meindert Sprang from http://www.customware.nl for helping me out on this unfortunate problem.