190-00228-08
GPS 16x Technical Specifications
Rev. C
Page 30
Each data member of the ephemeris data structure is indexed into the data array of the ephemeris packet and cast as
the appropriate data type. The indices are as follows (note that they correlate to the data members of the structure
respectively):
#define IDX_EPH_WN
0
#define IDX_EPH_TOC
4
#define IDX_EPH_TOE
8
#define IDX_EPH_AF0
12
#define IDX_EPH_AF1
16
#define IDX_EPH_AF2
20
#define IDX_EPH_URA
24
#define IDX_EPH_E
28
#define IDX_EPH_SQRTA 36
#define IDX_EPH_DN
44
#define IDX_EPH_M0
52
#define IDX_EPH_W
60
#define IDX_EPH_OMG0 68
#define IDX_EPH_I0
76
#define IDX_EPH_ODOT 84
#define IDX_EPH_IDOT 88
#define IDX_EPH_CUS
92
#define IDX_EPH_CUC
96
#define IDX_EPH_CIS
100
#define IDX_EPH_CIC
104
#define IDX_EPH_CRS
108
#define IDX_EPH_CRC
112
#define IDX_EPH_IOD
116
The last packet will be a “download complete” packet that will look like this:
TX Packet: Download Complete
Byte Description
Name
HEX Value
Delimiter
DLE
0x10
Download Complete ID
IOP_DL_CMPLT
0x0c
Number of bytes in data
SIZE
0x02
Ephemeris Download ID
IOP_DOWN_LOAD_EPH
0x5D
Pad
DATA
0x00
Checksum calculation
CHKSUM
----
Delimiter
DLE
0x10
End of packet
ETX
0x03
After properly acknowledging this packet (ACK the
IOP_DL_CMPLT
ID), the ephemeris download is complete.
