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APPENDIX B: GARMIN BINARY OUTPUT FORMAT
In binary output mode, the GPS 15xH/15xL will transmit packets once per second. The record
contains primarily post-process information such as position and velocity information. The default
serial port settings in binary output mode is 4800 baud, 8 data bits, 1 start bit, 1 stop bit and no
parity. Of those settings, only the baud rate may be changed. Please see Appendix C for details
on changing the baud rate in binary output mode.
To enable the binary output mode as a power-on default (powers up with this mode enabled), use
the $PGRMC1 NMEA 0183 sentence as described in
operating in NMEA 0183 mode in order for NMEA 0183 configuration sentences to have any
effect.) If you wish to enable the binary output mode and you do not wish to alter the setting for
which mode (NMEA 0183 or binary output) is enabled at power on, use the $PGRMO NMEA
0183 sentence as described in
found in the Garmin Device Interface SDK for details on how to form and parse Garmin packets,
available at https://www8.garmin.com/support/commProtocol.html.
Note that 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 72 hex for a satellite data record). 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. There is sample code at the end of this section that will strip off the DLEs and ETXs.
RS232 Packet:
- 0x10
- 0x##
- 0x##
- data bytes
- 0x##
delimiters)
- 0x10
- 0x03
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 data
for 12 satellites as described below.
typedef
struct
{
uint8
svid; //space vehicle identification (1–32 and 33–64 for
WAAS)
uint16
snr;
uint8
elev; //satellite elevation in degrees
uint16
azmth;
uint8
status;
} cpo_sat_data;
The status bit field represents a set of Booleans described below:
Bit
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.
Section
4.1.5. Refer to the Garmin Device Interface Specification
(DLE is first byte)
(Record ID – single byte)
(Number of data bytes – single byte)
(See descriptions below)
(2's complement of the arithmetic sum of the bytes between the
(DLE)
(ETX is last byte)
//signal-to-noise ratio
//satellite azimuth in degrees
//status bit-field
Meaning when bit is one (1)
27
Section
4.1.4. (You must currently be
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