Rikaline GPS-24/24A - Manual (Page 21)

GPS Receiver Board GPS-24 / 24A Operating Manual
Rikaline
Specifications subject to change without prior notice
Rikaline International Corp. 14F, 171, ChengGong Rd, Sanchong CityTaipei 241, Taiwan
Tel: ++886 2 8973 1899 Fax: ++886 2 8973 1896 E-Mail: [email protected] Web: www.rikaline.com.tw
Message
terminator <CR> <LF> 2 ASCII 13, ASCII 10.
C.11 $PNMRX301, Ephemeris Data Transfer
This message format is used to transfer the ephemeris data between nodes; it uses a packed hexadecimal
format to transfer ephemeris data for each of the available SV’s. Since the Ephemeris data is large and can
take time to transfer over a slow serial interface, the data is divided into individual messages for each of the
SV’s. These messages are transmitted sequentially and can be interleaved with other messages to prevent
the Ephemeris data blocking higher priority messages such as scheduled PVT information. The data for
these messages is expressed as signed or unsigned fixed point values which have been scaled from the
floating point values used in the position solution. The appropriate scaling factors are included in the table.
The ephemeris data for each satellite is divided into 3 separate messages with sequence numbers to
identify them, the contents of these frames reflects the contents of the appropriate subframes 1,2,3
transmitted from the SV’s. When transmitted these messages are generated in ascending order of SV Id and
sequence number, when being sent to the node these can be sent in any order, provided that the 3
messages for any individual satellite are grouped together, each message is individually interpreted and
after a group of 3 valid messages for an SV the ephemeris for that SV is updated independently. The 3
message formats are illustrated in the following tables
PNMRX301 message 1 field list
Field Format width scale Units Notes
Message ID $PNMRX301 8 PNMRX301 protocol header.
Satellite vehicle Id Int 2 Decimal satellite vehicle Id
from 1 to 32.
Subframe Id Int 1 Subframe number 1.
Week number Hex 3 Weeks 10 bit week number.
Health Hex 2 6 bits.
URA Hex 1 User range accuracy.
Time Group Delay Hex 2 2 -31 Seconds 8 bits.
IODC Hex 3 10 bit integer.
Toc Hex 4 2 -4 16 bits.
Af2 Hex 2 2 -31 sec/sec 2 8 bit signed integer.
Af1 Hex 4 2 -43 sec/sec 16 bit signed integer.
Af0 Hex 6 2 -31 Seconds 22 bit signed integer.
Checksum *xx (0) 3 2 digits.
Message
terminator <CR> <LF> 2 ASCII 13, ASCII 10.
PNMRX301 message 2 field list
Field Format width scale units Notes
Message ID $PNMRX301 8 PNMRX301 protocol header.
Satellite Vehicle Id Int 2 Decimal satellite vehicle id from
1 to 32.
Subframe Id Int 1 Subframe number 2.
Iode Hex 2 8 bits, lower 8 bits of matching
iodc.
Crs Hex 4 2 -5 Meters 16 bit signed integer.
Motion difference
( n) Hex 4 2 -43 Semi-
circles/sec
16 bit signed integer.
Mean anomaly Hex 8 2 -31 Semi- circles 32 bit signed integer.
Cuc Hex 4 2 -29 Radians 16 bit signed integer.
E Hex 8 2 -33 32 bit signed integer.
Cuc Hex 4 2 -29 Radians 16 bit signed integer.
Root A Hex 8 2 -19 Meters 1/4 32 bit signed integer.
Toe Hex 4 2 4 seconds 16 bit unsigned integer.
Checksum *xx (0) 3 2 digits.
Message
terminator <CR> <LF> 2 ASCII 13, ASCII 10.