Just wondering if someone can help me figure out how to obtain the starting bit from the NMEA 2000 literature. I am trying to add a pgn to my database, however the field numbers do not relate to the starting bit. How is this determined? For example, PGN 129025 has field values of 1 and 2 for lat and long, however the start bits are 1 and 5 respectively.

Jwendt,

The field numbers are not sent over the bus, they are just documentation. So there are two parameters in PGN 129025, field number 1 and 2.

The start bits 1 and 5 are actually start bytes. That means bytes 1 to 4 is latitude, 5 to 8 is longitude. The two parameters are 4 bytes long. You might need to expand the column Start Byte in the Parameters display to see the word Byte.

The way you determine the start byte and start bit is from the NMEA specification.