Using a Unabar ZAxis 2F dual frequency sounder, the output sentences are either echo trac DBT, NMEA XDR or DESO-20. Using serial2 as rangefinder, protocol as NMEA, baudrate as 115200 and orientation as 25 (facing down). It seems that even though the protocol NMEA is accepted not all of the strings are parsed by missionplanner. I have checked with Putty that there is indeed XDR data flowing into the PC and AP. Yes i have the rs232 output converted into TTL serial.