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Introduction
The MiniPlex-41USB is a four-channel NMEA multiplexer, enabling the connection of multiple NMEA-
0183 instruments to each other and a computer. Available are four NMEA inputs (
listener
-ports),
two NMEA outputs (
talker
-ports) and one USB port for connection with a computer.
Specifications:
Supply voltage:
5V
DC
from USB bus or
8 – 30 V
DC
, protected against reversed polarity.
Current consumption:
50 mA (100 mA max. with fully loaded talker ports).
Inputs:
4 x NMEA-183/RS-422, galvanically isolated.
Input resistance:
>800 Ohm.
Outputs:
1 x USB, 2 x NMEA-183/RS-422.
Buffers:
5 buffers of 1000 characters (4 x NMEA, 1 x USB).
NMEA Out1:
Combined data from NMEA inputs.
NMEA Out2:
Combined data from NMEA and USB inputs
or only from USB input.
Speed NMEA in:
4800 Baud.
Speed NMEA1/USB out:
4800, 9600, 19200 or 38400 Baud.
Speed NMEA2 out:
4800 Baud.
Indicators:
Overflow and Data.
Dimensions:
138 x 72 x 33 mm.
Housing:
Flame retardant ABS.
Operation
The MiniPlex-41USB reads NMEA sentences from the listener ports and stores them in a buffer, one
for each input. The sentences are read from the buffers in a round robin fashion, one sentence at a
time, giving each listener port equal priority. Each sentence is then sent to the talker ports and the
USB port.
The speed of the listener ports is fixed to 4800 Baud (= bits per second), which equals 480
characters per second. When all listener ports receive data at this rate, the buffers will not be
emptied in time and an overflow situation occurs. The red LED indicates this situation. When a
buffer is full, a partially received sentence will be discarded, to ensure that the MiniPlex-41USB
only sends complete and valid NMEA sentences.
There are two ways to resolve this overflow situation:
1. Configure the instruments on the listener ports to send less data or with greater intervals.
It is often possible to disable non-relevant sentences.
2. Increase the speed of the USB port on the MiniPlex-41USB. The maximum speed is 38400
Baud. From 19200 Baud and up (4 x 4800!) an overflow will never occur (except when in
Hub Mode).
The MiniPlex-41USB has two talker ports, ‘Out 1’ and ‘Out 2’. All received sentences from the
listener ports are available on talker port ‘Out 1’. Talker port ‘Out 2’ can be configured either to
output all received sentences from the listener ports and the USB port (Hub Mode), or only
sentences from the USB port (Server Mode).
