Garmin 15H-W - GPS, Technical Specifications

190-00266-01 

GPS 15H & 15L Technical Specifications  

Rev. D 

Page 24 

APPENDIX B: BINARY PHASE OUTPUT FORMAT 

In binary phase output mode, GPS 15H & 15L series products transmit two types of packets once per 
second. One record contains primarily post-process information such as position and velocity information. 
The second record contains receiver measurement information. For the GPS 15H & 15L, the records are 
sent at a default baud rate of 9600 baud, 8 data bits, and no parity.   

To turn these records on, use the $PGRMC1 NMEA sentence as described in section 

4 GPS 15H & 15L 

Software Interface

. (Refer to the 

Garmin GPS Interface Specification 

for details on how to form and parse 

Garmin packets. At the time of this printing, these specs are available from the technical support section of 
our Web site: 

http://www.garmin.com/support/commProtocol.html

.)   

Note

: The satellite data information is also enabled when the position record is enabled.   

Records sent over RS232 begin with a delimiter byte (10 hex). The second byte identifies the record type 
(33 hex for a position record and 34 hex for a receiver measurement). The third byte indicates 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 appear 
between the delimeters are escaped with a second DLE. Refer to the end of this section for sample code 
that strips off the DLEs and ETXs. 

RS232 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 Record 

The satellite data has a record ID of 0x72 with 84 (0x54) data bytes.  The data bytes contain the data for the 
12 channels as described below. For each satellite, the following data is available: 

typedef struct 

 { 

uint8 

svid; 

//space vehicle identification (1–32 and 33–64 for WAAS) 

uint16  

snr;  

//signal-to-noise ratio  

uint8 

elev; 

//satellite elevation in degrees 

 uint16 

azmth; 

//satellite azimuth in degrees 

uint8 

status; 

//status bit-field  

 } 

cpo_sat_data;