MFJ GPS INTERFACE INFO: The MFJ-1278B and MFJ-1278BT includes GPS code for sending one or two NMEA sentences to the unproto address. When placed in NMEA mode with a non-zero value in the NMEABCN parameter, the TNC sends the most recently received NMEA sentences that were received from the attached GPS. No other outgoing packets will occur except ID, BText, CTEXT, and mailbox data. NMEA is ASCII at 4800 baud, 8 bits, no parity, and 1 stop bit consisting of one or more types of sentences containing various types of data. ie: $GPRMC,034523,Y,02754.31,N,08023.03,W,1.5,035,031294,4W*23 034523 - - - - - - - - - - - - - - - - - - - - - - UTC time Y - - - - - - - - - - - - - - - - - - - - - Shows data is OK 02754.31,N - - - - - - - - - - - - - - - latitude 08023.03,W - - - - - - - - - - longitude 1.5 - - - - - - - - groundspeed. 035 - - - - - - heading degrees. 031294 - - dd/mm/yy. TNC NMEA Commands: NMeabcn n Periodicity for the GPS packet in 10's of seconds. If none of the selected sentences were received since power up, no packet is sent. N = 0 sets normal TNC operation. NMEA mode is enabled when non-zero and the TNC is powered up in the selected CONMODE. CONMODE "must" The TNC must be set to CONVERSE, SENDPAC to $0D, and CR to ON. NMEAFLT1 ssssss where sssss is the 5 character NMEA preamble. Note that NMEAFLT2 ssssss the leading $ is already assumed. ie: cmd: NMEAFLT1 GPGGA cmd: NMEAFLT2 GPZDA cmd: NMEAFLT2 % (this cancels the existing value) Notes: The TNC must be configured to 4800 baud to match the NMEA standard. NMEA defines a balanced RS-422 interface. Although this typically works when plugged directly into an RS-232 port, such operation is NOT guaranteed.