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Leadtek NMEA Protocol Manual For MTK NMEA INPUT/OUTPUT MESSAGE .......................................... 1 1.1 Prototype of NMEA Message.................................... 1 1.2 Checksum..................................................... 1 1.3 NMEA Output Message.......................................... 2 1.3.1 GGA—Global Positioning System Fixed Data ................. 3 1.3.2 GLL—Geographic Position - Latitude/Longitude ............. 4 1.3.3 GSA—GNSS DOP and Active Satellites ....................... 4 1.3.4 GSV—GNSS Satellites in View .............................. 5 1.3.5 RMC—Recommended Minimum Specific GNSS Data ............... 6 1.3.6 VTG—Course Over Ground and Ground Speed .................. 7 1.4 NMEA Input Messages.......................................... 8 1.4.1 Packet Type: 000 PMTK_TEST ............................... 9 1.4.2 Packet Type: 001 PMTK_ACK ................................ 9 1.4.3 Packet Type: 221 PMTK_SET_INTMT ......................... 10 1.4.4 Packet Type: 251 PMTK_SET_NMEA_BAUDRATE ................. 11 1.4.5 Packet Type: 300 PMTK_API_SET_FIX_CTL ................... 11 1.4.6 Packet Type: 301 PMTK_API_SET_DGPS_MODE ................. 12 1.4.7 Packet Type: 313 PMTK_API_SET_SBAS_ENABLED .............. 12 1.4.8 Packet Type: 314 PMTK_API_SET_NMEA_OUTPUT ............... 13 1.4.9 Packet Type: 320 PMTK_API_SET_PWR_SAV_MODE .............. 14 1.4.10 Packet Type: 330 PMTK_API_SET_DATUM ..................... 14 1.4.11 Packet Type: 400 PMTK_API_Q_FIX_CTL ..................... 14 1.4.12 Packet Type: 401 PMTK_API_Q_DGPS_MODE ................... 15 1.4.13 Packet Type: 413 PMTK_API_Q_SBAS_ENABLED ................ 15 1.4.14 Packet Type: 414 PMTK_API_Q_NMEA_OUTPUT ................. 15 1.4.15 Packet Type: 430 PMTK_API_Q_DATUM ....................... 16 1.4.16 Packet Type: 500 PMTK_DT_FIX_CTL ........................ 16 1.4.17 Packet Type: 501 PMTK_DT_DGPS_MODE ...................... 16 1.4.18 Packet Type: 513 PMTK_DT_SBAS_ENABLED ................... 17 1.4.19 Packet Type: 514 PMTK_DT_NMEA_OUTPUT .................... 17 1.4.20 Packet Type: 530 PMTK_DT_DATUM .......................... 17 . APPENDIX A: DATUM LIST ............................................ 18 2 © 2009 Leadtek Research Inc. All rights reserved. Preliminary Conf idential - Information is subject to change without prior notice. Leadtek NMEA Protocol Manual For MTK 1 NMEA Input/Output Message The unit may also output data in NMEA-0183 format as defined by the National Marine Electronics Association (NMEA), Standard For Interfacing Marine Electronics Devices, Version, January 1,1997. 1.1 Prototype of NMEA Message This NMEA input/output message is designed to include: Start Sequence: Start with character ‘$’ and behind it is the string representing message type. Payload: Datum collected to input/output and being separated with comma. Checksum: The value of checksum-algorithm. Start Sequence Payload Checksum End Sequence 1.2 Checksum The checksum is two-byte in the payload data. The following pseudo code defines the algorithm used. Let message to be the array of bytes to be sent by the transport. Index = 1 checkSum = 0 while message[ Index != ‘*’ ] checkSum ^= message[ index++ ] Checksum will skip the '$' character and then be calculated one character by one character using XOR(EXCLUSIVE-OR) operator to do so until getting '*' 1 © 2009 Leadtek Research Inc. All rights reserved. Preliminary Conf idential - Information is subject to change without prior notice. Leadtek NMEA Protocol Manual For MTK 1.3 NMEA Output Message The unit outputs the following messages as shown below (Table 1-1). Table 1-1 NMEA-0183 Output Messages Option Description Time, position, and fix related data for a GPS GGA receiver. Latitude and longitude of present position, time GLL of position fix and status. GPS receiver operating mode, satellites used in GSA the position solution, and DOP values. The number of GPS satellites in view satellite GSV ID numbers, elevation, azimuth, and SNR values. Time, date, position, course and speed data RMC provided by the GPS receiver. The actual course and speed relative to the VTG ground. 2 © 2009 Leadtek Research Inc. All rights reserved. Preliminary Conf idential - Information is subject to change without prior notice. Leadtek NMEA Protocol Manual For MTK 1.3.1 GGA—Global Positioning System Fixed Data 11 1 2 3 4 5 6 7 8 9 10 | 12 13 14 15 | | | | | | | | | | | | | | | $GPGGA,hhmmss.sss,llll.llll,a,yyyyy.yyyy,a,x,xx,xx.xx,xx.x,M,xx.x,M,xxxx,xxxx*hh 1. Time (UTC) 2. Latitude 3. N or S (North or South) 4. Longitude 5. E or W (East or West) 6. GPS Quality Indicator, 0 - fix not available, 1 - GPS fix, 2 - Differential GPS fix 7. Number of satellites in view, 00 – 12 8. Horizontal Dilution of precision 9. Antenna Altitude above/below mean-sea-level (geoid) 10. Units of antenna altitude, meters 11. Geoidal separation, the difference ...