Specifications

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yyyyy: Input field for NMEA Out2. Each ‘y’ represents an input, numbered from 1 to 4 from left to
right. Input 5 is not a real input but the source of NMEA sentences generated from
conversions. When ‘1’, the input is routed to output 2. When ‘0’, the input is not routed to
output 2.
b: Host data to NMEA Out2:
0: Host data is not routed
1: Host data is routed
2: Host data is routed and overrides data from the inputs. A time out mechanism
will route data from the inputs when no data from the host is received.
DRQ – Request Default Route
Requests the default route settings. The multiplexer responds with a DR sentence.
Format: $PSMDDRQ[*hh]<CR><LF>
FL – Filter
This sentence specifies a filter and routing rule that is applied on every incoming NMEA sentence.
Filter rules are specified using the address field of an NMEA sentence. For each filter rule, the
inputs on which the sentence may be received must be specified. Optionally, a divisor and an
output routing field can be added.
Sentences for which no rule exists are passed or blocked, depending on the filter mode set by field
‘f’ of the CF sentence.
Format: $PSMDFL,ccccc,xxxxx[,dd][yyyy][*hh]<CR><LF>
ccccc: Address field of the filter rule (e.g. ‘GPRMC’, ‘IIMWV’, etc). This field may contain wildcard
characters (‘-’). For instance, ‘GP---’ will apply to all sentences starting with ‘GP’.
Similarly, ‘--MWV’ will apply to all sentences ending on ‘MWV’ regardless of the Talker ID.
One filter rule with all wildcards and all inputs blocked is allowed to let the multiplexer
block all sentences for which no rule exists. When an all-wildcard rule is entered, the
multiplexer will not accept subsequent filter rules.
Example: $PSMDFL,-----,00000<CR><LF>
xxxxxx: Input field. Each ‘x’ represents an input to assign to this rule, numbered from 0 to 5 from
left to right. Input 0 is the host interface and inputs 1 to 4 represent NMEA inputs 1 to 4.
Input 5 is not a real input but the source of NMEA sentences generated from conversions.
A ‘1’ means that the sentence must be forwarded while a ‘0’ means that the sentence
must be blocked from that input.
dd: Optional divisor factor (0..99). The rate or frequency of a sentence is divided by this
number to reduce the number of sentences over time. If for instance a divisor of 6 is
specified, only every 6
th
occurrence of this sentence is passed.
yyyy: Optional routing field. Each ‘y’ represents an output the NMEA sentence must be routed
to. A ‘1’ routes the sentence to an output, a ‘0’ does not. Each digit represents one
output. From left to right, the outputs are NMEA Out1, NMEA Out2, Host and Wireless
interface.
When this field is omitted, a default of ‘1111’ is assumed, routing the specified sentence
to all outputs.
hh: Optional checksum
An FL sentence with the word DELETE in the ‘ccccc’ field erases all rules. An FL sentence with only
a ‘ccccc’ field will erase that entry. The filter accepts duplicate entries with the same ‘ccccc’ field to
allow separate routes from inputs to outputs.
Example: $PSMDFL,HEHDT,000110,5,1010<CR><LF>
This sentence specifies a rule for all sentences that have ‘HEHDT’ in the address field. It only
passes HEHDT sentences from inputs 3 and 4, the rate is lowered by a factor of 5 and the
sentence is routed to NMEA Out1 and the host only.