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190-00885-07 GPS 17x HVS Technical Specifications Rev. A
Page 21
APPENDIX B: GARMIN BINARY OUTPUT FORMAT
In Binary Output mode, the GPS 17x HVS will transmit packets once per second. The record is sent at a default
baud rate of 9600 baud, 8 data bits, and no parity.
To turn this record on, use the PGRMC1 NMEA sentence as described in section
4 GPS 17x HVS Software
Interface
. Refer to the Garmin Device Interface Specification found in the Garmin Device Interface SDK for details
on how to form and parse Garmin packets. At the time of this printing, these specs are available from the technical
suppport 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 hex
for a position record, 34 hex for a receiver measurement 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.
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.