User guide

C-GPS Overview and Usage
WM_DEV_C-GPS_APN_001-001
late: WM ACM F 007 level002 A P P L I C A T I O N N O T E A P P L I C A T I O N N O T E A P P L I C A T I O N N O T E
feature, the user should give AT+CONFIG=0 command
and then reset the Wireless CPU.
Using the above mentioned commands, the following steps should
be used to execute the sample applications:
1. Execute AT+WOPEN=1 command.
2. Set the password (if required) for authenticating the
configuration SMS using AT+PASSWORD command.
3. Set the availability of NMEA frames over the Debug
UART using AT+NMEA command.
4. Execute the AT+CGPS command to select the UART
which must be used by the C-GPS Daughter board. The
parameter given for the command must be coherent with
the switch position provided on the C-GPS Daughter
board. The C-GPS sample application will start at this
point of time and will take roughly 15 seconds to receive
the NMEA frames. If AT+NMEA command is configured
to display the NMEA frames over the Debug UART, then
the frames will be received over the UART after 15
seconds.
5. If the parameters set using AT+NMEA and AT+CGPS
commands are to be saved, then the command
AT+CONFIG=1 should be issued. In this case, after
Wireless CPU reset, the application would automatically
start using the saved parameters and there is no need
for the user to execute AT+NMEA and AT+CGPS
commands again. To prevent the Wireless CPU from
using the same configuration again and again (after
reset), the command AT+CONFIG=0 should be given
and the Wireless CPU should be reset.
6. The configuration SMS should be sent to the Wireless
CPU. If the password and the format of the configuration
SMS is correct, the PVT information will be sent to the
provided phone number.
Reference:
Please refer to the HTML help available in the
corresponding samples directory for more information on the
format of configuration SMS and the PVT information.
6 Annexes
This section provides vital statistical information regarding the
performance and NMEA Frame description.
6.1 Performances
6.1.1 Footprint
C-GPS ARM lib footprint
Memory Footprint:
• ROM : 245397 Bytes
• RAM (static): 106293 Bytes
C-GPS CPU load:
Normal mode
C-GPS 48%
C-GPS with NMEA frame 49%
Boost activated
C-GPS 40%
C-GPS with NMEA frame 45%
C-GPS GCC lib footprint
Memory Footprint:
• ROM : 304371 Bytes
• RAM (static): 29263 Bytes
C-GPS CPU load:
Normal mode
C-GPS 47%
C-GPS with NMEA frame 53%
Boost activated
C-GPS 40%
C-GPS with NMEA frame 45%
6.1.2 GPS
Open AT
®
SDK
v 4.11
Conditions Notes Value
Accuracy
-130
dBm(outdoor) In
dynamic mode
50% percentile 3,7 m CEP
-130
dBm(outdoor) In
dynamic mode
95% percentile 6,8 m CEP
-140 dBm In
dynamic mode
50% percentile 6,1 m CEP
-145 dBm In
dynamic mode
50% percentile
13,9 m
CEP
Velocity
Accuracy
Static mode First fix only 0,1 m/s Typ
Static mode
Continuous
fixes
0 m/s Typ
TTFF Hot Start Mean 3,5 s Typ
TTFF Warm
Start
Mean 30s Typ
TTFF Cold
Start
Clear Sky
conditions
Mean 38 s Typ
Clear Sky
conditions
95% percentile 45 s Typ
Update Rate -130 dBm
Continuous
fixes
1 Hz Typ
Desensitizatio
n due to GSM
Tx bursts
1 GSM burst
over 8 slots
Continuous
fixes
1,1 dB Typ
6.2 Description of NMEA Frames
NMEA 0183 standard defines the NMEA sentences and for each of
these sentences the first word, called a data type defines how the
rest of the sentence is interpreted. Each data has its own unique
interpretation, as defined by the NMEA standard.
Sentences vary in the information they contain. Some sentences
will repeat some of the information already provided, while others
provide new data.
Type of NMEA tags included in the C-GPS sample application are:
• $GPGLL Geographic Position, Latitude/Longitude
• $GPGSV GPS Satellites in View Data
• $GPZDA UTC Date & Time
• $GPGGA Global Positioning System Fix Data
• $GPVTG Course over ground and ground speed
• $GPGSA GPS DoP (Dilution of Precision) and Active
Satellites
• $GPRMC Recommended Minimum Specific GNSS
GPS/TRANSIT Data
This section describes what information is included in which NMEA
sentence and how to interpret various fields in the NMEA
sentence:
6.2.1 GLL (Geographic Position Latitude Longitude)
$GPGLL,llll.ll,E,yyyyy.yy,F,hhmmss.ss,A*hh
• llll.ll Destination waypoint latitude
• E N or S (for latitude)
• yyyyy.yy Destination waypoint longitude
• F E or W (for longitude)
• hhmmss.ss UTC of position fix (time)
• A Data Status (A = OK, V = Void)
• *hh Checksum
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Temp
6.2.2 GSV (Satellites in View Data)
$GPGSV,A,B,C,D1,E1,Az1,SNR1,D2,E2,Az2,SNR2,D3,E3,A
z3,SNR3,D4,E4, Az4,SNR4*hh