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Note that the multiplexer responds with a $PSMDWC sentence when it is in command mode. In normal
mode, a $PSMDWI response is given. A PSMDWI sentence without any parameters exits command mode.
When this sentence is issued in normal mode, a $PSMDWI,No response is returned.
Terminal Mode
Terminal Mode creates a direct connection between the wired and the wireless interface for testing and
debugging purposes. All other inputs and outputs of the multiplexer are inactive.
A $PSMDWI,T sentence enables Terminal Mode with the wireless module in Data mode. The blinking red
LED indicates Terminal Mode.
At this point, a direct connection exists and no NMEA commands are recognised by the multiplexer. The
connection is completely transparent and any (NMEA) data is passed in both ways. Three control codes
are implemented to control Terminal Mode:
Ctrl-q: Exit Terminal Mode. The wireless module will be set to Data mode and the multiplexer returns to
normal operation. The red LED is off.
Ctrl-c: Switch the wireless module to command mode, to control the configuration of the module through
the wired interface.
Ctrl-d: Switch the wireless module to data mode.
Cycling the power of the multiplexer also exits Terminal Mode.
Channel Information
When a Channel Information option is enabled, the multiplexer will output a standard NMEA Multiple Data
ID sentence or precede a sentence with a TAG block. Either of these contains the input number on which
the following NMEA sentence was received.
STN – Multiple Data ID
When STN sentences are enabled ($PSMDOP, option 11), the multiplexer transmits a $MXSTN sentence
before every NMEA sentence that is sent from the host interface.
Format: $MXSTN,xx*hh<CR><LF>
xx:
Input number, 00 to 05.
The Input Number indicates on which the following NMEA sentence was received. Input 00 represents
internally generated sentences and input 05 represents conversion results.
TAG Blocks
When TAG Blocks are enabled ($PSMDOP, option 12), the multiplexer adds a TAG block to every NMEA
sentence that is sent from the host interface. This TAG block has one source parameter, containing the
Unique Identifier (UI) of the multiplexer and the input the sentence was received on. This TAG block has
the following format:
\s:UI-x*hh\
where UI is the Unique Identifier of the multiplexer and ‘x’ is a digit from 0 to 5, representing the input
number. Input 0 represents internally generated sentences and input 5 represents conversion results. If
no UI is specified with the PSMDUI sentence, “MXnn” is sent, where “nn” are the last two digits of the
serial number of the multiplexer.
A heading sentence received on input 1 will be sent to the host as
\s:MX01-1*1E\$HEHDT,23.5*37<CR><LF>
