Garmin GPS 17HVS Technical Specifications - Page 34

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 Delimiter Download Complete ID Number of bytes in data Ephemeris Download ID Pad Checksum calculation Delimiter End of packet Name DLE IOP_DL_CMPLT SIZE IOP_DOWN_LOAD_EPH DATA CHKSUM DLE ETX HEX Value 0x10 0x0c 0x02 0x5D 0x00 ---0x10 0x03 After properly acknowledging this packet (ACK the IOP_DL_CMPLT ID), the ephemeris download is complete. 190-00228-21 GPS 16/17 Technical Specifications Page 30 Rev. A