now the good news: i managed to get a depth reading inside missionplanner.
i connected the TX and RX from serial port 4 from my pixhawk to an UART TTL → RS422 modifier. (see picture)
the NMEA 0183 cable from lowrance than is connected to this (the thicker wire with 4 smaller wires in blue,green,yellow,orange)
i set the lowrance output sentences to only “DPT” and a baudrate of 4800 (however, any baudrate should work i guess, as long as SERIAL4_BAUD is set the same.)
Great work - Can you give specifics for the pins on the serial port on Pixhawk and the setting in Mission planner. I have tried for a while and have not succeeded at this so this is great information.