Chapter 7 ___________________________________________________ Getting the data messages
VAISALA________________________________________________________________________ 53
NMEA 0183 V3.0 protocol
This section presents the data query commands and data message
formats for the NMEA 0183 v3.0 Query and automatic protocols.
For changing the message parameters, units and other settings, see
Chapter 8,
Sensor and data message settings.
A two character checksum (CRC) field is transmitted in all data
request sentences. For definition of the CRC, see Appendix C.
Device address (?)
This command is used to query the address of the device on the bus.
Command format:
?<cr><lf>
where
?
=
Device address query command
<cr><lf>
=
Command terminator
The response:
b<cr><lf>
where
b
=
Device address (default=0)
<cr><lf>
=
Response terminator.
Example:
?<cr><lf>
0<cr><lf>
If more than one transmitter is connected to the bus, see Appendix A,
Networking
. If you need to change the device address, see Chapter 6,
section
Changing the communication settings.
Acknowledge active command (a)
This command is used to ensure that a device is responding to a data
recorder or another device. It asks a sensor to acknowledge its
presence on the bus.
Command format:
a<cr><lf>
where
a
=
Device address (default = 0)
