Garmin GPS 18x Series Technical Specifications

Also see for GPS 18x LVC: Declaration of conformity

Contents

Garmin GPS 18x Series Technical Specifications Manual pdf 16 page image

190-00879-08 GPS 18x Technical Specifications Rev. BPage 124 GPS 18x PC, GPS 18x LVC, & GPS 18x-5Hz SOFTWARE INTERFACEThe interface protocol design of the GPS 18x PC, LVC, and GPS 18x-5Hz products is based on the National MarineElectronics Association’s NMEA 0183 ASCII interface specification. This standard is fully defined in NMEA 0183,Version 2.30. Copies may be obtained from NMEA, www.nmea.org.In addition to the standard NMEA 0183 sentences, the GPS 18x PC, LVC, and GPS 18x-5Hz may also beconfigured to transmit information over their serial interface using NMEA 0183 compliant Garmin proprietarysentences. These proprietary sentences begin with the characters, “$PGRM”, instead of the characters “$G” that aretypical of the standard NMEA 0183 sentences. The characters “$P” indicate that the sentence is a proprietaryimplementation and the characters and “GRM” indicate that it is Garmin’s proprietary sentence. The letter (orletters) that follow the characters “$PGRM” uniquely identifies that particular Garmin proprietary sentence.It is also possible to configure the GPS 18x PC, LVC, and GPS 18x-5Hz to transmit binary data information overtheir serial interface. See Appendix B: Garmin Binary Output Format for details.The GPS 18x USB does not transmit NMEA sentences: It transmits using the Garmin USB interface. The GarminUSB interface is discussed in the Garmin Device Interface Specification found in the Garmin Device Interface SDKlocated on the Garmin Web site at: www.garmin.com/support/commProtocol.html.You can configure the GPS 18x USB to transmit binary data information over the USB interface. Refer to AppendixB: Garmin Binary Output Format.The following sections describe the NMEA 0183 data format of each sentence transmitted and received by the GPS18x PC, LVC, and GPS 18x-5Hz products.4.1 RECEIVED NMEA 0183 SENTENCESThe following paragraphs define the sentences that can be received on the GPS sensors’ port. Null fields in theconfiguration sentence indicate no change in the particular configuration parameter. All sentences received by theGPS sensor must be terminated with , the ASCII characters for carriage return (0D hexadecimal) andline feed (0A hexadecimal). The checksum *hh is used for parity checking data and is not required, but isrecommended for use in environments containing high electromagnetic noise. It is generally not required in normalPC environments. When used, the parity bytes (hh) are the ASCII representation of the exclusive-or (XOR) sum ofall the characters between the “$” and “*” characters, non-inclusive. The hex representation must be a capital letter,such as 3D instead of 3d. Sentences may be truncated by after any data field and valid fields up to thatpoint will be acted on by the sensor.4.1.1 Almanac Information (ALM)The $GPALM sentence can be used to initialize the GPS sensor’s stored almanac information in the unlikely eventof non-volatile memory loss or after storing longer than six months without tracking GPS satellites.$GPALM,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<1> Total number of ALM sentences to be transmitted by the GPS sensor during almanac download.This field can be null or any number when sending almanac to the GPS sensor.<2> Number of current ALM sentence. This field can be null or any number when sending almanacto the GPS sensor.<3> Satellite PRN number, 01 to 32<4> GPS week number<5> SV health, bits 17–24 of each almanac page<6> Eccentricity<7> Almanac reference time<8> Inclination angle<9> Rate of right ascension<10> Root of semi major axis<11> Omega, argument of perigee<12> Longitude of ascension node<13> Mean anomaly<14> af0 clock parameter<15> af1 clock parameter