u-blox ANTARIS 4 - Page 84


your position is our focus
Th followingtablege ivesinformationaboutthevariousvalues:
Nu bm er Formats
Short Comment Min/Max Resolution Type Size (Bytes)
U1 0...255 1 UnsignedChar 1
I1 plement -128...127 1SignedChar 1 2'scom
U2  0...65535 1 UnsignedShort 2
I2 2'scomplement -32768...32767 1SignedShort 2
U4 0…4'294'967'295 1 UnsignedLong 4
I4
plement
-2'147'483'648...
2'147'483'647
1
SignedLong
4
2'scom
R4
-1*2^+127…2^+127
~Value*2^-24

IEEE754Single
Precision
4
R8 8
-1*2^+1023...2^+1023
~Value*2^-53

IEEE754Double
Precision
CH
ASCII/ISO8859.1
Encoding
1


Table 25: Internal Field Number Formats
UBX h
The tingandincludingtheCLASSfield,upuntil,butexcluding,the
Che

C ecksum
checksumiscalculatedoverthepacket,star
cksumField:

Figure 71: UBX Checksum range
The checksum algorithm used is the 8-Bit Fletcher Algorithm, which is being used in the TCP standard (RFC
1145).Thisalgorithmworksasfollows:
Buffer[N]containsthedataoverwhichthechecksumistobecalculated.

ThetwoCK_valuesare8-BitUnsignedIntegers,only!Ifyouimplementitwith
larger-sizedintegervalues,make
suretomaskbothCK_AandCK_Bwith0xFFafterbothoperationsintheloop.
CK_ A = 0, CK_B = 0;
For(i=0; i<N; i++)
{
CK_A = CK_A + Buffer[i];
CK_B = CK_B + CK_A;
}
Aftertheloop,weenduphavingtwoUINT8 values,whicharetransmittedattheendofthepacket.
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) ReceiverDescription
GPS.G4-MS4-05007-A1
  Page 84