Garmin GPS 19x HVS Technical Specifications

Also see for GPS 19x HVS: Installation instructions

Garmin GPS 19x HVS Technical Specifications Manual pdf 25 page image

25APPENDIX B: GARMIN BINARY OUTPUT FORMATIn Binary Output mode, the GPS 19x HVS will transmit position packets at the rate of positioning update rate andsatellite information packets once every second. The record is sent at a default baud rate of 9600 baud, 8 data bits,and no parity. For operation at positioning update rate of 10 times per second the baud rate may have to benegotiated to a higher one to avoid loss of packets.To turn this record on, use the PGRMC1 NMEA sentence as described in section 4 GPS 19x HVS SoftwareInterface. Refer to the Garmin Device Interface Specification found in the Garmin Device Interface SDK for detailson how to form and parse Garmin packets. At the time of this printing, these specs are available from the technicalsuppport section of our Web site: www.garmin.com/support/commProtocol.html.Records sent over RS-232 begin with a delimiter byte (10 hex). The second byte identifies the record type (33 hexfor a position record, 34 hex for a receiver measurement and 72 hex for a satellite data record). The third byteindicates the size of the data. The fourth byte is the first byte of data. The data is then followed by a checksum byte,a delimiter byte (10 hex), and an end-of-transmission character (03 hex). Additionally, any DLEs (0x10) that appearbetween the delimeters are escaped with a second DLE. There is sample code at the end of this section that will stripoff the DLEs and ETXs.RS-232 Packet:- 0x10 (DLE is first byte)- 0x## (Record ID – single byte)- 0x## (Number of data bytes – single byte)- data bytes (See descriptions below)- 0x## (2’s complement of the arithmetic sum of the bytes between the delimiters)- 0x10 (DLE)- 0x03 (ETX is last byte)The data bytes of each packet contain the record specified by the record ID. A description of each record follows.Satellite Data RecordThe satellite data has a record ID of 0x72 with 84 (0x54) data bytes. The data bytes contain data for 12 satellites asdescribed below.typedef struct{uint8 svid; //space vehicle identification (1–32 and 33–64 forSBAS(WAAS/EGNOS/MSAS) )uint16 snr; //signal-to-noise ratiouint8 elev; //satellite elevation in degreesuint16 azmth; //satellite azimuth in degreesuint8 status; //status bit-field} cpo_sat_data;The status bit field represents a set of booleans described below:Bit Meaning when bit is one (1)0 The unit has ephemeris data for the specified satellite.1 The unit has a differential correction for the specified satellite.2 The unit is using this satellite in the solution.This pattern is repeated for 12 satellites for a total of 12 X 7 bytes = 84 (0x54) bytes.The RS-232 Packet for the Satellite Record looks like:- 0x10 (DLE is first byte)- 0x72 (Record ID – single byte)- 0x54 (Number of data bytes – single byte)- 12 cpo_sat_data records