Actisense NDC-4, Install & User Manual

NMEA Data Multiplexer - NDC-4

Page 5

© 2015 Active Research Limited

General Features

4/5 Opto-isolated Input Ports

Each Opto-isolated input port has a priority level. This 

defaults  to  the  logical  order  matching  the  port  numbers, 

i.e. port 1 has the highest priority and port 4 has the lowest. 

When the USB cable is not plugged in (or not powered), 

OPTO IN 0 can be used as a fifth fully compliant NMEA 

0183 data input, appearing last in the priority list.

2 ISO-Drive Output Ports

These outputs combine the input data into standard NMEA 

outputs with independent Baud rate selection options, 

defaulting to 4800 (OUT 1) and 38400 (OUT 0). If the 

combined Baud rate of all NMEA inputs exceed the output 

Baud  rate,  it  is  possible  that  the  combined  data  could 

exceed the data carrying capacity of the NMEA output 

channel. The multiplexer contains special software to 

ensure that when the output channel is overloaded, new 

data of the same type as older data, still in the buffer, will 

overwrite the older sentence. 

A PC RS232 or USB Bidirectional Port

The RS232 compatible Port 0 (OPTO IN 0 plus ISO OUT 

0) and the USB interface ensures that any device (or PC), 

that has an RS232 or USB port, receives all the input 

NMEA data, and can add its own NMEA data to ISO OUT 

1.  This  allows  for  the  possibility  of  a  “virtual  cockpit”  of 

instruments displaying all available data in any manner the 

user requires (available from a number of manufacturers). 

These connections also allow the unit to be updated via 

the freely available ActiPatch flash upgrade software that 

will be made available on the 

Actisense

 website when the 

NDC-4 firmware has been enhanced.

Notes:

1. 

When the USB cable is plugged in and powered up, it 

disables OPTO IN 0 on the NDC-4.

2. 

NDC-4 variants that don’t come with a USB cable can 

be upgraded by purchasing a USB Upgrade Kit.

Technical Features

Flash ROM technology

 that supports automatic 

programming for quick and easy updates, 100,000+ erase 

cycles and a 10 year Data Retention provides carefree 

user configuration. 

On-chip memory store

  allows  buffering  of  short-term 

NMEA data, allowing the unit to smooth short-term peaks 

in the NMEA data flow.

A diagnostic LED

 indicates the operation mode of the 

NDC-4, if any faults have been detected, or the peak load 

currently on any one of the NMEA inputs. 

High-speed 32-bit ARM processor

 capable of up to 40 

million instructions per second.

The NMEA 0183 inputs

 are galvanically opto-isolated 

differential inputs, protecting against common mode 

voltage differences of up to 2500v. Fully compliant with the 

NMEA  0183  standard  specification  and  compatible  with 

RS232, RS422 and RS485 signal levels. The typical 

operating voltage is 2.0v to 15.0v and can wit/- 

35v continuously and +/- 40v transients. Compatible with 

both differential and single ended inputs. 

ISO-Drive output technology

 unique to 

Actisense

, 

protects against common mode voltage differences of up 

to  1500v.  The  output  automatically  changes  between 

differential and single ended drive depending upon the 

type of instrument it is connected to. Fully compliant with 

the  NMEA  0183  standard  specification  and  compatible 

with RS232, RS422 and RS485 signal levels.

Wide battery input voltage range

 to offer maximum 

compatibility, the NMEA 0183 NDC-4 can operate from a 

battery supply anywhere between 8 and 35 volts.

USB powered

 option is available when the battery source 

is not present. When the main battery is present, the USB 

power drain is minimal. 

WARNING:

 The USB and battery 

grounds are not isolated, see 

“USB Warning” on page 9

.

Very tough Polycarbonate case

  is  certified  to  IP66  

(Protection against heavy seas, or powerful jets of water), 

the  addition  of  non-acid  based  marine  sealant  to  the 

gasket can increase this to IP67 (Protection against 

immersion).  Being  Polycarbonate,  it  is  also  incredibly 

strong, offering a wide temperature range and superior 

protection to the electronics inside. 

Robust Nylon grommets

 are certified to IP68 (Protection 

against complete, continuous submersion in water).

Note:

 To achieve this level of water integrity all glands 

must  be  occupied  by  round-section  cables  of  between 

4.5mm and 10 mm or be replaced by blanking plugs.

Large range of possible cable diameters

  of  between 

4.5 mm and 10 mm, single or multi-pair wire types can be 

easily accepted.

An NMEA 0183 Checksum 

will be added to any sentence 

received without one to ensure that they can be accepted 

by an NMEA 0183 Listener that expects a checksum.  This 

feature makes the NDC-4 essential even when interfacing 

a single v.1.5 NMEA 0183 Talker to a v.2.0 (and above) 

NMEA 0183 Listener.