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.
GPS 16x Technical Specifications | Rev. A | |
| Page 29 |
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