Pin designations are shown below. Jumper locations are shown for LK1 and LK2. Your Bathy-500MF will accept NMEA 0183 input sentences containing GPS postiton in either GGA or GLL format. The unit auto detects when GGA is present in a sentence and accepts such as its first choice of position.
Serial input is made to the same hardware pins as is used for GPS input.
Simply put, the sequence is shown below. This output emulates the ODOM Echotrac output sentence as shown in the example below. Note that zeroes are suppressed. The structure for this industry standard output is shown below. NMEA dbt Data output will be NMEA 0183 depth below transducer sentence format as shown below.