Company Confidential
39
Raveon Technologies Corp.
EIA-422A but for most purposes it is RS-232 compatible. Use 4800 bps, 8 data
bits, no parity and one stop bit ( 8N1 ) for standard NMEA data.
NMEA 0183 sentences are all ASCII characters. Each sentence begins with a
dollar sign ($) and ends with a carriage return linefeed (<CR><LF>). Data is
comma delimited. All commas must be included as they act as markers. Some
GPS do not send some of the fields. A checksum is added to the end of the
message. Following the $ is the address field aaccc. aa i
s the device id. “GP” is
used to identify GPS data. Transmission of the device ID is usually optional. ccc is
the sentence formatter, otherwise known as the sentence name.
The
RF-7800W
supports the NMEA standard WPL, TLL, GGA, and GSV
sentences. The Raveon proprietary PRAVE sentence is sent out of the
RF-7800W
in GPS mode 2. It is used by PC software programs to track
RF-7800W
transponders, and process their status information.
12.3. $PRAVE Raveon Proprietary Message, Location-Status
The $PRAVE message is sent out the
RF-7800W
when it is configured for
GPS 2
mode of operation. This mode is typically used with the RavTrack PC program, or
other computer programs that can process position and status information. [[[It is
sent at 38.4K bytes/second out the serial port.]]]
Along with ID and position information, it contains a host of other status
information. The length of this message may exceed he standard NMEA limit of 79
characters. Any product or software that uses this message must take this into
account.
Following is a list of the fields sent in this message
Field
Usage
Comments
1
$PRAVE
Raveon Proprietary Header
2
From ID
The ID of the transponder that transmitted its position over the air. It
is a decimal number, 0 – 9999.
3
To ID
The ID that this position report was sent to. It is a decimal number, 0
– 9999.
4
Latitude
dddmm.mmmm format. It is signed. + is north, - is south. No sign
means north. Note: typically there are 4 decimal places, but as few
as 0 decimal places are possible. Null field if no GPS lock.
5
Longitude
dddmm.mmmm format. It is signed. + is east, - is west. No sign
means east. Note: typically there are 4 decimal places, but as few as
0 decimal places are possible. Null field if no GPS lock.
6
UTC time
The UTC time at the time the transmission was made. Hhmmss
format. Null field if no GPS lock.
7
GPS Status
0=not valid position. 1=GPS locked and valid position. 2=Differential
or WAAS fix.
8
Num Satellites
The number of satellites in view
9
Altitude
The altitude in meters. Null field if no GPS lock.
