I still feel it would be more reliable to use the available NMEA
data from the tablet´s own GPS and port it to your installed OpenCPN prog. After all,there´s dozens of apps using the local GPS data.
There is a free utility which ´creates´ apps,or rather copies EVERY typed sequence and from this produces an automatic app. Perhaps this could be used?
The trick is to be able to catch the NMEA
datastream and feed it to OpenCPN´s data port.
You could try catching the NMEA datastream produced by the FREE ´GPS Data Monitor´app which will also store the captured data in a file for later testing. You can download it as an .APK file.
Not sure it would be any easier to capture and feed the NMEA data using a bluetooth GPS device. You would also then occupy the only USB port on the tab which needs a USB ´dongle´inserted.
See attached screenshot of the datastream collected and saved.