Noland Engineering N183-41 User manual

NoLand Engineering, Inc.
N183-41 Serial Multiplexer Installation & Operation Manual
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General Description
Each N183-41 Serial Multiplexer provides four NMEA-0183 opto-isolated listener ports
and one talker port. Multiple units may be interconnected to provide additional listener
ports (i.e., two units will provide seven listener ports and three units will provide ten lis-
tener ports).
The talker port enables the computer to send "query" messages to instruments
equipped with a "listen" port, such as a LORAN or GPS receiver. The Talker port util-
izes a standard RS-422 differential driver as specified by the Standard.
A standard RS-232 interface is provided for connection to the host computer. The de-
fault baud rate is 4800 so that is also NMEA-0183 compatible. The N183-41 is fully
compliant with the National Marine Electronics Association NMEA-0183 Standard for
Interfacing Marine Electronic Devices, Version 2.00, 1992.
Installation
Installation of the N183-41 requires connection to a power source (8-16VDC), the in-
struments, and the computer. All connections are made via a 16-pin terminal strip as
detailed below: (See Fig. 1)

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N183-41 Serial Multiplexer Installation & Operation Manual
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Power/Ground Connection
The power (+12V) and ground (GND) connections are located at one end of the terminal
strip. It is recommended that these be connected to the same power source (e.g., circuit
breaker) such as the ships instruments and/or computer, since it will be used only when
both the instruments and computer are also in use. There is no ON/OFF switch provided
on the N183-41 due to its low power consumption.
NMEA 0183 listener Connections
The N183-41 input connections are labeled "IN1" through "IN4". When connecting in-
struments to the N183-41, it is important to maintain the proper polarity of the lines.
Connect the "A" terminal of each input port of the N183-41 to the corresponding "+" or
"A" output terminal of each instrument. Connect the "B" terminal of each input port of the
N183-41 to the corresponding "-" or "B" output terminal of each instrument.
CAUTION: Do not interconnect the "B" terminals of the N183-41 and instruments as
some instruments use single ended drivers and some use differential. This will not dam-
age the N183-41, but could cause erratic operation and may damage the instruments.
NOTE: If a particular instrument has only
one NMEA terminal, it can be assumed that
it is a single ended active line. In this case,
connect this line to the "INA" terminal of the
N183-41 and connect the corresponding
"INB" terminal of the N183-41 to instrument
ground.
NMEA 0183 talker Connection
The N183-41 also features a talker (TLK)
port which may be connected to all instru-
ments with an NMEA 0183 listener port
such as a LORAN or GPS receiver. Con-
nection of this port follows the same con-
vention as above except that any shield
connection is now made at the N183-41
rather than at the instrument. Also note that
multiple listeners may be connected to this
(TLK) talker port.
RS-232 Computer Connection
For most applications the N183-41 RS-232
output (RX, COM, and TX), will be con-
nected to a computer via the DB-9 connec-

NoLand Engineering, Inc.
N183-41 Serial Multiplexer Installation & Operation Manual
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For installations which require more than four instruments to be interfaced, multiple N183-41's
may be used. Two or three N-183-41's may be interconnected as shown in Fig. 3 to provide
seven and ten listener ports respectively. In this case the RS-232 output of one N183-41 may be
used to drive an
input (listener)
port of a second
N183-41. For
NMEA 0183
compatibility,
the connection
should be made
as shown in Fig.
2(c).
Mounting
Three through
holes are pro-
vided for mount-
ing the N183-41
to any conven-
ient surface. Al-
though the unit is
watertight, it is
best to mount it
away from direct
sunlight and/or
water spray to
prevent exces-
sive heating of
the unit or corro-
sion of the termi-
nals. If the
N183-41 is ex-
posed to exces-
sive humidity, it
is recommended
that the terminal
connections be
treated with an
anti-corrosion
compound.

NoLand Engineering, Inc.
N183-41 Serial Multiplexer Installation & Operation Manual
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Operation
The listener (IN1A,IN1B,....IN4A,IN4B) ports
The N183-41 features four independent NMEA-0183 listener ports. Each port receives data
from the instrument connected to it on a character-by-character basis and is stored in memory
exclusive to that port. Upon reception of a complete message, (i.e., a string of ASCII characters
terminated by a [CR][LF]), the message is transferred to the RS-232 output. Messages from each
input port are transferred to the output in the order that they are completed.
The talker (TLKA,TLKB) port
The N183-41 features one NMEA-0183 talker port. The N183-41 receives data to be sent out of
the talker port from the host computer via the RS-232 port on a character-by-character basis
storing the data in the talker buffer until a complete message is received. (A complete NMEA
0183 message is defined as a string of ASCII characters beginning with a $, and terminated by a
[CR][LF]. (See the Appendix A for details.) As soon as a complete message is received from the
computer, it is transmitted out the talker port.
The RS-232 (RX,COM,TX) port
A standard RS-232 port is provided for the communication interface to the host computer. This
port is intended for transmitting and receiving NMEA-0183 listener/talker messages to and from
the host computer. This port is also compatible with NMEA-0183 at its default setting of 4800
baud. Listed below are a series of control characters which are available to the host for control-
ling the N183-41:
^R = Reset the N183-41
^S = Stop sending data
^C = Restart sending data
^H = Change Baud rate from 4800-9600
^L = Change Baud rate from 9600 to 4800
Note: On initial power-up, the N183-41 defaults to 4800 Baud and automatically sends data
once it is received without any user intervention.
Programming
This section describes the communication protocol and programming features of the N183-41.
Data Acquisition
Acquiring data from marine navigational instruments is the primary function of the N183-41.
Under the NMEA 0183 specification, all data is transmitted as fields of ASCII characters assem-
bled into specific messages. The format of every NMEA 0183 message is defined the standard.
There are three basic sentence structures defined by the standard;

NoLand Engineering, Inc.
N183-41 Serial Multiplexer Installation & Operation Manual
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talker sentence
query sentence
proprietary sentence
talker Sentence
The general format for a talker (instrument) message is:
$ttsss,df1,df2,....[CR][LF]
All messages start with a Dollar sign ($) and are terminated with a Carriage Return/ Line feed
([CR][LF]). Between these are the actual data fields (df1,df2,...) of the messages. The data
fields are separated (delimited) by commas.
The first field always consists of a five character string immediately following the "$" sign and
is termed the address field. The first two characters are termed the talker identifier while the
next three are the sentence identifier. The sentence type identifier defines the remaining data
fields, (i.e., the number of fields and whether they are fixed or variable length).
query Sentence
A query message is intended to request approved messages to be transmitted from a talker. For
example, a query message might be sent to a GPS receiver to request "DISTANCE-TO-
WAYPOINT" information be transmitted.
The general format of a query message is:
$ttllQ,sss,[CR][LF]
Where the first two characters of the address field are termed the talker identifier of the re-
quester and the next two characters are the talker identifier of the device being queried
(listener). The fifth character is always a "Q" defining the message as a query. The next field
(sss) contains the three letter mnemonic of the sentence being requested.
Proprietary Sentence
Proprietary sentences are those used by manufacturers which are not pre-defined by the stan-
dard.
The general format of a proprietary message is
$Pmmm,df1,df2,...,[CR][LF]
Where the "P" indicates that it is a proprietary message and that the data fields which follow do
not necessarily correspond to any approved sentence structure. The "mmm" is defined as the
manufacturers message code.
For more information, see the NMEA 0183 Description.

NoLand Engineering, Inc.
N183-41 Serial Multiplexer Installation & Operation Manual
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Troubleshooting
In general, most users will find the installation and operation of the N183-41 to be trouble-free.
However, if faults should arise, the following procedures are recommended to diagnose the
problem:
The majority of faults with electronic equipment are due to worn or incorrect wiring. In case of
trouble, the following should be checked first:
Power Supply Connections
Instrument Connections
RS-232 Interface
If all connections seem to be correct and a suitable ammeter is available, the power supply cur-
rent should be checked. The power supply current should be approximately 0.075A (75 ma.).
Any reading significantly above or below the figure indicate a defective unit which must be re-
placed. Please contact NoLand Engineering for further assistance.
An ammeter may also be used as a quick check on the instrument connections. Connect the me-
ter to the input terminals of the N183-41 (output from instrument}, and the meter should flicker
about once per second as data is transmitted from the instrument. This works best if the meter is
a low voltage AC setting.
Once you are sure that the supply current is correct and that data is being received, you can
measure the RS-232 output in the same manner as above. In this case, connect the ammeter to
the 'TX' and 'COM' terminal and watch for the once per second flicker indicating data transmis-
sion.
Warranty
NoLand Engineering, Inc., provides a two year replacement warranty against manufacturing
faults or component faults. A dated purchasing receipt must be provided.
RED to "TX" of N183-41
GRN to "COM" of N183-41
ORG to "RX" of N183-41
No Connection to "SHLD" of N183-41