Garmin GPS 17N Technical Specifications - Page 36

Browse online or download pdf Technical Specifications for Marine GPS System Garmin GPS 17N. Garmin GPS 17N 40 pages. Gps 16/17 series
Also for Garmin GPS 17N: Technical Reference (30 pages), Declaration Of Conformity (1 pages), Installation Manual (8 pages)

Garmin GPS 17N Technical Specifications
An example function to do the parsing is shown below. Note that the double data types are converted by the
function cnvt_ieee_double(). This function merely swaps the upper and lower words of the double.
This is necessary on GPS 15, 16, 17 series sensors due to a compatibility issue with the IEEE floating point
standard): In this example, the array m_TempArray contains the data portion of the ephemeris packet
(with DLE stuffing removed).
/****************************************************************************
*
*
PROCEDURE NAME:
*
copyData - ephemeris data unpacker
*
*
DESCRIPTION:
*
unpacks data from ephemeris packet DATA field after extraneous DLEs
*
have been removed.
*
integer type.
*
****************************************************************************/
void GPM_ephList::copyData
(
GPM_ephData* pTemp
)
{
pTemp->EphStruct.wn
pTemp->EphStruct.toc = *(float*)&m_TempArray[IDX_EPH_TOC];
pTemp->EphStruct.toe = *(float*)&m_TempArray[IDX_EPH_TOE];
pTemp->EphStruct.af0 = *(float*)&m_TempArray[IDX_EPH_AF0];
pTemp->EphStruct.af1 = *(float*)&m_TempArray[IDX_EPH_AF1];
pTemp->EphStruct.af2 = *(float*)&m_TempArray[IDX_EPH_AF2];
pTemp->EphStruct.ura = *(float*)&m_TempArray[IDX_EPH_URA];
cnvt_ieee_double((long *)&m_TempArray[IDX_EPH_E]);
pTemp->EphStruct.e = *(double*)&m_TempArray[IDX_EPH_E];
cnvt_ieee_double((long *)&m_TempArray[IDX_EPH_SQRTA]);
pTemp->EphStruct.sqrta = *(double*)&m_TempArray[IDX_EPH_SQRTA];
cnvt_ieee_double((long *)&m_TempArray[IDX_EPH_DN]);
pTemp->EphStruct.dn = *(double*)&m_TempArray[IDX_EPH_DN];
cnvt_ieee_double((long *)&m_TempArray[IDX_EPH_M0]);
pTemp->EphStruct.m0 = *(double*)&m_TempArray[IDX_EPH_M0];
cnvt_ieee_double((long *)&m_TempArray[IDX_EPH_W]);
pTemp->EphStruct.w = *(double*)&m_TempArray[IDX_EPH_W];
cnvt_ieee_double((long *)&m_TempArray[IDX_EPH_OMG0]);
pTemp->EphStruct.omg0 = *(double*)&m_TempArray[IDX_EPH_OMG0];
cnvt_ieee_double((long *)&m_TempArray[IDX_EPH_I0]);
pTemp->EphStruct.i0 = *(double*)&m_TempArray[IDX_EPH_I0];
pTemp->EphStruct.odot = *(float*)&m_TempArray[IDX_EPH_ODOT];
pTemp->EphStruct.idot = *(float*)&m_TempArray[IDX_EPH_IDOT];
pTemp->EphStruct.cus = *(float*)&m_TempArray[IDX_EPH_CUS];
pTemp->EphStruct.cuc = *(float*)&m_TempArray[IDX_EPH_CUC];
pTemp->EphStruct.cis = *(float*)&m_TempArray[IDX_EPH_CIS];
pTemp->EphStruct.cic = *(float*)&m_TempArray[IDX_EPH_CIC];
pTemp->EphStruct.crs = *(float*)&m_TempArray[IDX_EPH_CRS];
pTemp->EphStruct.crc = *(float*)&m_TempArray[IDX_EPH_CRC];
pTemp->EphStruct.iod = *(unsigned char*)&m_TempArray[IDX_EPH_IOD];
return;
}
/* copyData */
190-00228-20
Note that sint16 refers to a signed 16-bit
/* ephemeris data unpacker
/* pointer to ephemeris data array
= *(sint16*)&m_TempArray[IDX_EPH_WN];
GPS 16/17 Technical Specifications
Page 32
*/
*/
Rev. C