Actisense NBF-2-A User Manual

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NMEA Buffer

NBF-2-A

User Manual

Issue 1.03

 1 Galvanically opto-isolated NMEA 0183 “Listener” data input

for complete isolation of the input from ground, meeting all

the specications of the latest NMEA 0183 / IEC61162-1&2 specications.

 6 ISO-Drive “Talker” outputs, compatible with both NMEA 0183

(RS422 / RS485) and RS232 listeners.

 Compatible with NMEA 0183 standard and “HS” (AIS) baud rates,

and speeds well in excess of this for special applications.

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NMEA Buffer - NBF-2-A

Contents

Important Notices 4 Notices 4 Foreword 4 Introduction 4 NMEA 0183 Introduction 5

Electrical specications 5

Technical features 5 Connecting devices together 6

The basics 6 The NMEA signals 6 The different NMEA standards 6

Connections 7 Input Connections 8

NMEA 0183 Input 8 Connecting to the battery supply 8

Output Connections 9

NMEA 0183 / RS422 Outputs 9

Troubleshooting guide 10 Specications 11 Company Information 12

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Important Notices

Actisense and the Actisense logo are registered trademarks

of Active Research Limited. All rights are reserved. The contents of this manual may not be transferred or copied without the expressed written permission of Active Research Limited. All other trademarks are the property of their respective owners.

The Actisense NMEA Data Buffer (NBF-2) is intended for use in a marine environment, primarily for below deck use. If the unit is to be used in a more severe environment, such use may be considered misuse under the seller’s warranty.

The NBF-2 has been certied to comply with the European directive for Electro-Magnetic Compatibility (EN60945), and is appropriately CE marked. Operation of the unit should be in conjunction with appropriate CE approved shielded connectors and cabling used in accordance with the CE directive EN60945. Any EMC related issues should be reported to Active Research immediately to allow the company to rectify or resolve EMC related problems in accordance with its obligations under EN60945.

Foreword

Actisense recognises that instructions are often skipped,

so we have aimed to write this document in an informative, yet direct manner that will aid the user. We have tried to cover all the points a typical user may need to know. Please read all sections before installing and using the Actisense NMEA Buffer product and any related software

programs.

Introduction

The Actisense NMEA 0183 Buffer (NBF-2) product was developed to solve a common problem: wanting to share the NMEA information from an NMEA device with more than two other NMEA instruments. Most NMEA output’s (e.g. GPS) can only drive 1 or 2 NMEA devices, any more and the signal becomes degraded and corruption of the

NMEA data occurs.

The Actisense NMEA Buffer solves all NMEA buffering problems by allowing distributed buffering of one NMEA instrument’s data output to a large number of other NMEA device inputs, and if required, even a PC’s RS232 port.

If the unit is connected such that compliance failure occurs

beyond the company’s control, the company shall not be held responsible for compliance failure until suitable EMC guidelines for connection are seen to have been taken.

Notices

When using this document, keep the following in mind:

The products described in this manual and the specications thereof may be changed without prior notice. To obtain upto-date information and/or specications, contact Active

Research Limited or visit the Actisense website (www.

actisense.com).

Active Research Limited will not be liable for infringement

of copyright, industrial property right, or other rights of a

third party caused by the use of information or drawings described in this manual.

Active Research Limited will not be held responsible for

any damage to the user that may result from accidents

or any other reasons during operation of the user’s unit

according to this document.

Utilising fourteen years of experience in the marine industry in creating market leading depth sounders and

other NMEA products, Actisense recognised the need to

produce a full galvanic Opto-isolated, dependable NMEA buffering solution that meets, and indeed surpasses, all of

the NMEA 0183 requirements.

Full information on the complete Actisense product range

can be found on the Actisense website.

The NBF-2 does not validate the NMEA data it receives in any way. Neither the NMEA sentence checksum, nor the data contained within the NMEA sentence is validated. Therefore, the electronic device(s) supplying the NBF-2 with NMEA data retain(s) the sole responsibility for the NMEA data’s validity.

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NMEA 0183 Introduction

NMEA Buffer - NBF-2-A

Designed over 20 years ago, the NMEA 0183 standard has slowly become the common method by which marine electronics devices talk to one another. The standard species both the electrical connections that make up an

NMEA system and the format of the data sentences that carry the NMEA information.

The NMEA 0183 standard is a purely digital data transmission scheme, using ‘1’s and ‘0’s in a binary format,

to communicate a digital representation of the required

information (depth, speed etc.) to connected instruments.

Electrical specications

The latest specications for NMEA 0183 (version 2 onwards) are similar to the RS422 standard. They use +5v and 0v signalling, which is low voltage and can be interfaced to computer equipment (with an Actisense

Opto-isolated adapter cable). In older equipment

(version 1) however, voltage levels could be much greater (up to +/- 15v) as the original specication used 12-15 volt +/- signalling, which is similar to the standard RS232

computer serial communication ports.

The NMEA 0183 specication also requires that all receiving equipment must be Opto-isolated; this Opto-

isolation requirement reduces the chances of interference

and removes the problem of ground loop effects.

Wide battery input voltage range to offer maximum compatibility, the NBF-2 can operate from a battery supply anywhere between 8 and 45 volts.

Very low power consumption that is typically 43mA with no load and 100mA with all 6 outputs maximally loaded (on a 12 volt system). This will reduces to 25mA and 50mA respectively on 24 volt systems.

Very tough Polycarbonate case is certied to IP66 (classied as “totally protected against dust and protection against low pressure jets of water from all directions”). Being Polycarbonate, it is also incredibly strong, offering a wide temperature range and superior protection to the

electronics inside.

The IP66 rating of the case is only limited by the sealing gasket strip, which can be enhanced by applying a suitable non-acid based marine sealant to the gasket after wiring and testing. This will allow use of the unit in areas where

salt spray could enter, accidental immersion may occur,

or in environments where maximum long-term reliability is

paramount.

Robust Nylon grommets are certied to IP68 (classied as immersible for long periods without water ingress). Note that to achieve this level of water integrity all grommets must be occupied by round-section cables.

Technical features

The NMEA 0183 input is a galvanically opto-isolated

differential input to fully comply with the NMEA 0183 standard specication. This allows the input to work correctly with long cable runs and in a noisy environment. Typical operating voltage is 2.0v to 15.0v. The unit can withstand +/- 35v continuously, and +/- 40v transients. The Opto-isolator can protect any upstream equipment (chart plotter, laptop PC, radar etc.) from up to 2500v of common

mode voltage difference.

Removes all problematic ground loops between the

NMEA device connected to the NBF-2 input port, and all the NMEA devices connected to the output ports.

The NBF-2 is equipped with 6 ISO-Drive outputs. ISODrive output technology creates a driver, unique to

Actisense, that is isolated to 1500 volts. ISO-Drive creates a completely oating talker output, making safe connection to a PC an easy task.

The output automatically changes between differential and

single ended drive depending upon the type of instrument

it is connected to. The ISO-Drive output is fully compliant with the NMEA 0183 standard specication and is also compatible with RS232 signal levels.

Large range of possible cable diameters of between

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

easily accepted.

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Connecting devices together

The basics

NMEA data is transmitted from an information source such

as GPS, depth sounder, gyro compass etc. These data

sending devices are called “Talkers”.

Equipment receiving this information such as a chartplotter, radar or NMEA display is called a “Listener”.

Unfortunately, only one Talker can be connected on to a single NMEA 0183 system at any one time. Two or more Talkers are simply not possible because they are not synchronised to each other, and will attempt to ‘talk’ at the same time (over each other), resulting in corruption of the NMEA data, and potentially in disaster if valuable data

such as navigation information is lost or corrupted so that

it is incorrect and/or misleading.

This fundamental problem with the NMEA system can be easily overcome, and multiple Talkers connected together,

using the Actisense NMEA Data Multiplexer “NDC” series of instruments. If the required system has multiple NMEA

Talker device of the same type (e.g. two GPS units), the highest priority device can be automatically switched using

the Actisense Autoswitch (NSW-1).

Please visit the Actisense website for full details on these and other Actisense products.

This connection method is referred to as “single ended” instead of the “differential” method used by NMEA 0183

v2.0 devices.

The data format is largely the same between both systems, with v2.0 adding some extra sentence strings, and removing older (redundant) sentence strings from the specication. The situation is further complicated, as many manufacturers still use the old (“single ended”) method of connection because it is cheaper to implement.

So how can an older type NMEA device be connected to a newer type device?

Care is needed – it is possible to damage or overload the output of a newer differential device if it is incorrectly connected to an older device. This is because the older devices used ground as the return, whereas the newer devices actually drive the NMEA “-/B” line between 5v and 0v. Thus, connecting this output to ground will result in high currents being drawn by the driver instrument, resulting in

potential overheating and damage to the driver circuits.

To connect a new type differential device to an old type

single-ended system, connect the NMEA “+/A” output from the differential driver to the single-ended NMEA “Rx” or “In” input of the device. Leave the NMEA “-/B” output oating.

Connect the ground line of the differential output device to the ground of the single-ended device. This provides the

required data signal return current path.

The output drive capability of many instruments means that often their NMEA outputs can only drive one or two Listeners. In this case, the output of the Talker can be boosted to ‘talk’ to six listeners simultaneously using the

Actisense NMEA Buffer.

The NMEA signals

The NMEA 0183 system v2.0 and later uses a ”differential” signalling scheme, whereby two wires are used to transmit the NMEA data. These connections will be labelled as

either NMEA “A” and “B“ or NMEA “+” and “-“ respectively, depending on the instrument and manufacturer.

When connecting between different manufacturers, there can be some confusion, but it is simple and easy to remember: NMEA “A” connects to NMEA “+” and NMEA

“B“ connects to NMEA “-“.

The different NMEA standards

The NMEA 0183 specication has slowly evolved over the years, so connecting one device to another is not always a straight forward matter. The earlier versions of NMEA 0183 (before v2.0, as detailed above), used slightly different connection methods and signal levels: the instruments had just one “NMEA” data line (‘Tx’ or ‘Out’), and used the ground as the other line - similar to the way a computer serial port works.

To connect an old type single-ended device to a new type

differential device, connect the NMEA ”Tx” or “Out” output from the single-ended driver to the differential NMEA “+/A” input of the device. Connect the ground line of the single-ended output device to the NMEA “-/B” input of the

differential device. This provides the data signal return current path. If the NMEA “-/B” input is left oating, then data corruption / errors may occur.

The Actisense NBF-2 is equipped with ISO-Drive outputs which removes all of these problems. Because the ISODrive output “oats”, this means that it will automatically adjust to the voltage of the line it is connected to. Thus, it simplies installation work, as you no longer need to check

on the type of input used on the equipment that the NBF-2

is connected to. You can connect the “B/-” connection of the NBF-2 to ground or to a differential “B/-” input without worry - the voltage levels will simply adjust themselves to be correct.

Please refer to the Output Connections section for

example of these connection methods.

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Connections

NMEA Buffer - NBF-2-A

NMEA BUFFER

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Figure 1 – All external connections

The NMEA Buffer (NBF-2) has screw-terminal “Phoenix” type external connections for: -

1. An NMEA 0183 “Listener” port

The NMEA 0183 input is of the differential optoisolated type and uses the unique Actisense low current drain circuitry (2mA @ 2.0v) to conform in full with the NMEA 0183 marine electronic device network communication standard, and is exible enough to

interface to most full and partially compliant devices.

2. Six ISO-Drive “Talker” ports Each output comprises of two connections: ‘+/A’

and ‘-/B‘, and conforms in full to the NMEA 0183

standard, and can be connected safely to NMEA 0183 v1,2,3,HS RS-232, RS-422 and RS-485 type

listeners.

3. Battery supply input.

NBF-2-A

Note:

1. To complete the NMEA 0183 standard all device interconnection NMEA cables used should meet the two-conductor, shielded, twisted pair conguration specication. The shield connection of these wires should be connected at the instrument end only to

prevent ground loops.

2. Refer to the Specications section for the full details

on input/output specications.

3. If the laptop / PC to be used with the NBF-2 does not have an RS232 serial port available, the Actisense USG-1 USB to Serial Gateway and the USB-1 USB to RS232 adapter cable have been tried and tested to provide a compatible communications port. Please

visit the Actisense website for full details on this, and other Actisense products.

4. Higher quality cable will naturally yield higher performance / higher Signal-to-Noise Ratio (SNR).

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NBF-2-A

NMEA BUFFER

Input Connections

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Battery /

Power Supply

NMEA

Talker A

Figure 2 – Input connections

NMEA

Talker B

NMEA 0183 Input

The NMEA 0183 differential opto-isolated input is designed to handle a variety of NMEA 0183 talker specications. Please determine (from device manufacturer’s information) if the device required to be connected to

the Actisense NBF-2 conforms in full to the NMEA 0183

network communication standard. If it does not, the exible Actisense NBF-2 inputs should still be capable of interfacing with the device, though this is not guaranteed.

The diagram (gure 2) above shows a typical installation with both fully compliant NMEA devices with differential

outputs, and non-differential devices that output NMEA using the ground line as the “NMEA -” line.

Please note that only one NMEA device can be connected to “NMEA IN” at any one time.

NMEA Talker device A: This device conforms in full

to the NMEA 0183 standard and shares the same

connection ID’s as the Actisense NBF, so connection is a simple matter of matching ID’s (refer to gure 2).

Tx G

Personal

Computer

Personal Computer: A PC’s RS232 output may be directly connected to the NBF-2. This allows a PC to drive many NMEA instruments from its RS232 port without risk of damage or overload, and creates isolation from the PC ground. Simply connect the PC’s

“Tx” pin (Pin 3 on 9-pin D-type connector) to the NBF’s “+/A” and its “Ground” (Pin 5 on D-type) to the “-/B”.

Connecting to the battery supply

The Actisense NBF-2 should be wired to the vessel’s battery supply in the most direct manner possible, to minimize interference from other electronic devices. The cable used should be of sufcient gauge to handle the power requirements of the Actisense NBF-2 (refer to the

Specications sections).

Note:

1. Wire colours are for guidance only.

NMEA Talker device B: This is a single ended (nondifferential) device and does not conform completely to the NMEA 0183 standard. However, by connecting ‘+‘ to ‘+/A‘ and its ‘G/Ground’ to the NBF “-/B”, the NBF should be able to receive the NMEA data correctly.

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Output Connections

NMEA Buffer - NBF-2-A

Personal Computer

NMEA Listener 5

NMEA BUFFER

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Figure 3 – Output connections

NMEA 0183 / RS422 Outputs

The NMEA 0183 / RS422 buffered outputs are capable of

driving more than 10 fully NMEA 0183 compliant listening

devices each. In practice, however, it is better to connect just one NMEA listener per output to maintain the isolation between each output. Figure 3 shows one possible

conguration of this preferred connection, using a

range of typical listeners that may be encountered.

NBF-2-A

In practice, this is rare, as most equipment is designed

to work well below this voltage level.

Personal Computer: The NBF-2 ISO-Drive outputs are compatible with most personal computer RS232 port inputs. Connect PCs ‘Rx’ (Pin 2 on a standard 9Pin D-type) to NBFs ‘A/+’ and its ’G/Ground’ (Pin 5 on D-type) to the NBFs ‘B/-’.

Listener 4

Listener 3

Listener 2

Listener 1

NMEA

NMEA Listener devices 1, 2, 3 and 4: These devices

conform in full to the NMEA 0183 standard and their

connection ID’s match that of the NBF-2. Simply connect like for like (“+” to “+”, “A” to “A” etc.). Examples of both listener labelling types are shown.

NMEA Listener device 5: This device does not

conform in full to the NMEA 0183 standard and is a “single-ended device”. Connection of single-ended

devices to a differential output used to be done with caution, but the NBF-2 now makes this risk free.

Simply connect devices input, (which may be labelled

‘+‘ or ‘Rx’) to the NBF ‘+/A‘, and its ‘G/Ground’ to the the NBF ‘-/B’.

The listener device should now be able to receive the NMEA data correctly. This is not guaranteed, though, as the instrument may have been designed to require more than the 5v signal of the NBF-2 drive output.

Note: The PC will “see” a single-ended signal swinging between plus and minus 5v. This is more than enough for most PC receiver chips, which will normally operate successfully down to +/-2v.

Note:

1. Wire colours are for guidance only.

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Troubleshooting guide

This guide will concentrate on all relevant troubleshooting issues above simple cable connection faults. Therefore, the cables between the NBF-2 hardware and any other devices should be checked as a matter of course, before continuing with this guide.

Problem / Error condition Required user response

Ensure that correct polarity of the NMEA connections have been observed - NMEA connections are polarity sensitive.

No data seen on

NMEA instrument display

No data seen on

PC display

“+” and “A” connections should be wired to the NBF’s “+/A”. “-” and “B” connections should be wired to the NBF’s “-/B”.

No damage should be caused if the polarity is reversed, but no NMEA data will be seen on the receiving instrument.

Ensure that the PC software is selecting the correct PC Comms port number and baud rate.

As a diagnostic, you can use the standard Windows “HyperTerminal” utility to receive NMEA data. By setting the

input comms port to the one the NMEA NBF-2 is connected to,

the baud rate to that required (4800 normally), no parity, 1 stop bit, 8 data bits and no ow control, the received NMEA text data from the NBF-2 will be shown on the PC screen.

Table 1 – Troubleshooting guide

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NMEA Buffer - NBF-2-A

Specications

Parameter Conditions / Note Min. Max. Unit

Supply

Supply voltage (note 1) 8 45 V

Supply current no-load / full load (note 2,3)

OPTO Isolated Flexible Input

Supply voltage = 12v 43 100 mA

Supply voltage = 24v 25 50 mA

Input voltage between +/-

Input current

Differential input voltage Minimum level for data detection 1.8 2.0 V

Galvanic isolation Between input and ground 2500 V

ISO-Drive Flexible Output (RS-422, RS-485 and RS-232 compatible)

Output voltage between ISO Out +/A and ISO Out -/B (under no load)

Output current (note 2,3)

Output short circuit current (note 4) 50 55 mA

Galvanic isolation Between output and ground 1500 V

Other parameters

Baud rate 115.2 Kbit/sec

Data propagation delay (typical) 1.7 2.1 us

General

Ambient temperature -20 +70 °C

Logical ‘1’ / stop bit -15.0 0.5 V

Logical ‘0’ / start bit 4.0 15.0 V

Maximum is under +35v overload

condition, min @2.0v input level

Logical ‘1’ / stop bit -4.8 -5.2 V

Logical ‘0’ / start bit 4.8 5.2 V

At maximum load, drive voltage reduces to approx 2.7v

1.6 9.0 mA

- 27 mA

Table 2 – NBF-2 specications

All specications are taken with reference to an ambient temperature (TA) of +25°C.

Note:

1. Continuous supply voltage. The PSU used on the NBF-2 is a high specication switch-mode regulator, which can operate for short periods at up to 80v, allowing the unit to easily pass the “SAE J1113” transient test, where a transient impulse peaking at 80v is applied.

2. Current consumption measured under no-load and full-load conditions

3. “Full Load” is dened on a 100 ohm loads on each of the six ISO-Drive outputs, resulting in a net output current of approximately to 162mA to all outputs.

4. Short circuit may be applied indenitely. The ISO-Drive output may be short-circuited directly to a 30 volt battery supply without damage. A maximum current of 50mA will ow due to “polyfuse” auto-resetting fuse technology being used in each output.

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Order codes:

NBF-2 Standard NBF-2 (1 isolated input, 6 ISO-Drive outputs)