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Appendix C
Phase Output Data Binary Format
Two records are transmitted once per second by the GPS 35LP. One record contains primarily post-
process information such as position and velocity information. The second record contains receiver
measurement information. The records are sent at a default baud rate of 9600 baud, 8 bits, no parity.
Records begin with a delimiter byte (10 hex). The second byte identifies the record type (28 hex for a
position record, 29 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 chksum byte, a delimiter byte (10
hex), and an end-of-transmission character (03 hex).
Note - If RTCM-104 differential data is sent to the GPS 35LP the board will reset the Phase Output Data
baud rate to the same baud rate used for RTCM-104 data. If the differential inputs are used on the GPS
35LP then the RTCM-104 data must be sent to the GPS 35LP at 9600 baud(preferred) or 4800 baud.
RTCM-104, baud rates less than 4800 baud are not supported by the GPS 35LP since it would limit bus
bandwidth past the point where a once per second phase output data rate could be maintained.
Position Record
- 0x10 (dle is first byte)
- 0x28 (position record identifier)
- 0x36 (size of data)
- cpo_pvt_type (see description below)
- one byte chksum (the addition of bytes between the delimiters should equal 0)
- 0x10 (dle)
- 0x03 (etx is last byte)
typedef struct
{
float alt;
float epe;
float eph;
float epv;
int fix;
double gps_tow;
double lat;
double lon;
float lon_vel;
float lat_vel;
float alt_vel;
} cpo_pvt_type;
alt ellipsoid altitude (mt)
epe est pos error (mt)
eph pos err, horizontal (mt)
epv pos err, vertical (mt)
fix 0 = no fix; 1 = no fix; 2 = 2D; 3 = 3D; 4 = 2D differential; 5 = 3D differential;
6 and greater - not defined
gps_tow gps time of week (sec)