Thanks for the suggestion... I managed to install Navmon and it's reading all the NMEA data I get from my Shipmodul Multiplex-Lite device via USB on COM5. Including my NMEA0183 HDG reading from my fluxgate compass
I can imagine, on the NMEA Monitor
"Serial A >>" and "Serial A <<" values are what is being sent and received from and to Serial A.
Under "NMEA Options - Internally-generated NMEA Sources" I have HDM set to ON. On "NMEA Routing" I configured for the row "Source: Serial A" the column "Serial A: Send".
I get the following info on the NMEA monitor
Serial A << $IIHDM,307.,*5B
Serial A >> $IIHDM,307.,*5B
However, it doesn't show up on my B&G display :/
Any troubleshooting ideas?