– –
– –
16
17
VTG – Course Over Ground and Ground Speed
Figure 15 contains the values for the following example:
$GPVTG,79.65,T,,M,2.69,N,5.0,K,A*38
Course Over Ground and Ground Speed Example
Name
Example
Units
Description
Message ID
$GPVTG
VTG protocol header
Course over ground
79.65
degrees
Measured heading
Reference
T
TRUE
Course over ground
degrees
Measured heading (N/A, null field)
Reference
M
Magnetic
Speed over ground
2.69
knots
Measured speed
Units
N
Knots
Speed over ground
5.0
km/hr
Measured speed
Units
K
Kilometer per hour
Mode
A
A=autonomous, D=DGPS, N= Data
not valid
Checksum
*38
<CR> <LF>
End of message termination
Figure 15: Course Over Ground and Ground Speed Example
NMEA Input Messages
The following outlines the serial commands input into the module for
configuration. By default, the commands are input at 9,600bps, 8 data bits,
1 start bit, 2 stop bits, and no parity.
All fields in all proprietary NMEA messages are required; none are optional.
All NMEA messages are comma delimited. Figure 17 outlines the message
identifiers supported by the module.
Serial Data Structure
Name
Example
Description
Start Sequence
$PSRF
Message ID
<MID>
Message Identifier consisting of three numeric
characters. Input messages begin at MID 100.
Payload
DATA
Message specific data.
Checksum
CKSUM
CKSUM is a two-hex character checksum as
defined in the NMEA specification, NMEA-0183
Standard for Interfacing Marine Electronic Devices.
Checksums are required on all input messages.
End Sequence
<CR> <LF>
Each message must be terminated using Carriage
Return (CR) Line Feed (LF) (\r\n, 0x0D0A) to cause
the receiver to process the input message. They
are not printable ASCII characters, so are omitted
from the examples.
Figure 16: Serial Data Structure
Message ID Values
Name
MID
Description
SetSerialPort
100
Set PORT A parameters and protocol
NavigationInitialization
101
Reset the modules
Query/Rate Control
103
Query standard NMEA message and/or set
output rate
LLANavigationInitialization
104
Reset the modules
Development Data On/Off
105
Development Data messages On/Off
System Turn Off
117
Performs an orderly shut down of the module
and switches into hibernation mode
Figure 17: Message ID Values
