NMEA Multiplexer Owners Handbook
Document Number: 81250-1 Date: February 2005
Copyright Raymarine (UK) Ltd 2005

Preface

Congratulations on having bought a Raymarine NMEA Multiplexer. This enables you to combine NMEA outputs from up to four devices, to provide a combined output to four other devices.
CAUTION: Electrical safety
Make sure you have switched off the power supply before you start installing this product.

Important information

To the best of our knowledge, the information in this handbook was correct when it went to press. However, Raymarine cannot accept liability for any inaccuracies or omissions it may contain. In addition, our policy of continuous product improvement may change specifications without notice. Therefore, Raymarine cannot accept liability for any differences between the product and this guide.
EMC Installation Guidelines
All Raymarine equipment and accessories are designed to the best industry standards for use in the recreational marine environment. Their design and manufacture conforms to the appropriate Electromagnetic Compatibility (EMC) standards, but correct installation is required to ensure that performance is not compromised. Although every effort has been taken to ensure that they will perform under all conditions, it is important to understand what factors could affect the operation of the product. The guidelines given here describe the conditions for optimum EMC performance, but it is recognized that it may not be possible to meet all of these conditions in all situations. To ensure the best possible conditions for EMC performance within the constraints imposed by any location, always ensure the maximum separation possible between different items of electrical equipment.
For optimum EMC performance, it is recommended that wherever possible: Raymarine equipment and cables connected to it are: At least 3 ft (1 m) from any equipment transmitting or cables carrying radio signals e.g. VHF radios, cables and antennas. In the case of SSB radios, the distance should be increased to 7 ft (2 m). More than 7 ft (2 m) from the path of a radar beam. A radar beam can normally be assumed to spread 20 degrees above and below the radiating element. The equipment is supplied from a separate battery from that used for engine start. Voltage drops below 10 V in the power supply to our products, and starter motor transients, can cause the equipment to reset. This will not damage the equipment, but may cause the loss of some information and may change the operating mode. Raymarine specified cables are used. Cutting and rejoining these cables can compromise EMC performance and must be avoided unless doing so is detailed in the installation manual. If a suppression ferrite is attached to a cable, this ferrite should not be removed. If the ferrite needs to be removed during installation it must be reassembled in the same position.

Suppression Ferrites

The following illustration shows typical cable suppression ferrites used with Raymarine equipment. Always use the ferrites supplied by Raymarine.
Connections to Other Equipment
If your Raymarine equipment is to be connected to other equipment using a cable not supplied by Raymarine, a suppression ferrite MUST always be attached to the cable near the Raymarine unit.

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Contents
Preface... i CAUTION: Electrical safety.. i Important information... i EMC Installation Guidelines.. i Suppression Ferrites... ii Connections to Other Equipment. ii Introduction... 1 Inputs & outputs.. 1 NMEA inputs.. 2 Input priorities... 2 NMEA outputs... 2 Installation... 3 Mounting.... 3 Connections... 4 Real-time or buffered inputs.. 4 NMEA in... 4 NMEA out.... 5 Power supply.. 6 CAUTION: Electrical Safety.. 7 Securing cables... 7 Indicators... 7 Data indicator lit.. 7 Overflow indicator lit.. 7 Both indicators lit... 8 Maintenance.... 8 Disposal... 8 Specifications... 9

Introduction

The Raymarine NMEA Multiplexer combines data from up to four NMEA-0183 devices to provide a single, multiplexed NMEA output.

Inputs & outputs

The NMEA Multiplexer has: Four NMEA inputs (listener-ports), NMEA In 1, 2, 3 & 4. One NMEA output (talker-port), NMEA Out One common terminal NMEA Out Com.
NMEA In 1a NMEA In 1b NMEA In 2a NMEA In 2b NMEA In 3a NMEA In 3b NMEA In 4a NMEA In 4b NMEA In Shld

NMEA-0183 Multiplexer

Overflow
NMEA Out a NMEA Out b NMEA Out Com NMEA Out Shld Not used PWR +12/24V GND

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NMEA inputs
Each NMEA in (listener) port is a differential pair across terminals a and b, and can receive NMEA data from one device. The speed of each listener port is fixed at 4800 baud. NMEA data on listener ports 1 and 2 is multiplexed in real time (i.e. unbuffered). NMEA data on listener ports NMEA In 3 and 4 is fed via a discrete buffer for each port. Each buffer holds approximately 2 seconds of NMEA data.

Input priorities

Data at the listener ports is prioritized, so that each NMEA in port is read twice as often as the next one. Thus for example, data at input 1 is read in twice as often as data at input 2, four times as often as input 3 and eight times more often than input 4.

NMEA outputs

The NMEA Out (talker) port is a differential pair across terminals a and b, and feeds multiplexed NMEA data from all the NMEA inputs, to up to four products.

Installation

Mounting
As the NMEA Multiplexer is not waterproof, it must be fitted in a location where it will not come into contact with water. Secure the NMEA Multiplexer to a suitable surface, as shown in the following illustration.
1. Place the NMEA Multiplexer at the intended location and mark holes for fixing screws. 2. Drill two 1/8"(3.4 mm) pilot holes for NMEA Multiplexer screws.

Da ta Ov erflo w

3. Countersink pilot holes to prevent damage to the mounting surface.
4. Secure the NMEA Multiplexer with the screws provided.

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Connections
Real-time or buffered inputs
Before connecting NMEA inputs to your NMEA Multiplexer, consider whether they should be connected as real time or buffered inputs: Data running at a fast rate and consisting of single sentences, particularly time-critical data, should be connected to either NMEA In 1 or NMEA In2, real time inputs. This includes data from devices such as Fast Heading Sensors, and Fluxgate Compasses. When data is processed in real time, some sentences may be lost, but the timing of the data is maintained and there is no time delay. These inputs will store only one NMEA sentence at a time, and thus prevent unwanted delays. Slower data that is input as a burst should be connected to either NMEA In 3 or NMEA In 4, as buffered inputs. This includes data such as GPS, route and depth information, for which the timing is less critical. These inputs can store multiple sentences (12 to 70, depending on length). This is necessary for devices such as GPS, which can output 10 sentences at once, every 1 or 2 seconds.

NMEA in

Connect an unused pair of NMEA In a and b terminals on the NMEA Multiplexer to the NMEA output port of each device from which you wish to receive NMEA data. The manner in which the connections are made depends on whether the device has a differential or single ended output, as follows:
Device with differential NMEA output & shield connection NMEA out + NMEA out Shield Device with differential NMEA output but no shield connection NMEA out + NMEA out -

Cable shield

NMEA Multiplexer NMEA In a NMEA In b
NMEA Multiplexer NMEA In a NMEA In b Shld
Note: NMEA outputs from Raymarine products are differential.
Device with single-ended NMEA output NMEA out +

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Ground

NMEA out

Connect the a and b terminals of the NMEA Out connector to the listening ports of up to four devices to which you wish to transmit multiplexed data. The manner in which the connections
6 are made depends on whether the device has a differential or single ended output, as follows:
Cable shield Device with differential NMEA input NMEA in + NMEA in -
NMEA Multiplexer NMEA Out a NMEA Out b Shld
Note: NMEA inputs on Raymarine products are differential.
NMEA Multiplexer NMEA Out a NMEA Out Com Shld
Device with single-ended NMEA input NMEA in + Ground

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Power supply
The NMEA Multiplexer operates from a dc supply voltage in the range 8 V to 30 V and provides protection against reversed polarity. It is recommended to connect the NMEA Multiplexer to the same power source or circuit breaker as the ships instruments and/or computer. Protect the power supply with a 0.5 A fuse. The wires used to connect the power supply must be less than 50 m in length and have a total cross-sectional area of at least 0.2 mm2. The following examples represent the minimum requirement:
AWG single-strand wire. 7/0.2 multi-strand wire, i.e. 7 strands, each of 0.2 mm diameter
CAUTION: Electrical Safety
Before connecting power to the NMEA Multiplexer, turn off the power supply. Connect either a 24 V or 12 V power supply, via a 0.5 A fuse, as follows:
0.5 A fuse +12 V or +24 V 0V NMEA Multiplexer PWR +12/24V

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Securing cables
When you have connected all cables, use appropriate cable ties and/or clamps to make sure the cables are physically secure and cannot be accidentally pulled from their connectors.

Indicators

Data indicator lit
A green Data LED blinks when valid NMEA data is received at the listener ports, to indicate satisfactory connection and polarity of the connected device. The Data LED will not blink if the input polarity is reversed.

Overflow indicator lit

A red Overflow LED indicates a buffer overflow, i.e. that more data is coming in than can be transmitted. When a buffer is full,
8 partially received sentences will be discarded, to ensure that the NMEA Multiplexer only passes complete and valid sentences. You may be able to resolve this overflow situation if you: Set up the devices on the listener ports to send less data or data at greater intervals. If possible, disable non-relevant sentences. Swap the input devices to different listener ports.

Both indicators lit

Both LED s will blink once when power is applied to the NMEA Multiplexer. If the red LED stays lit, this indicates that a hardware error was found during self-test.

Maintenance

There are no user-serviceable parts inside the Raymarine NMEA Multiplexer. However periodically check to ensure that the connections to it are secure, and that the condition of the connecting cables is satisfactory.

Disposal

When you want to dispose of this product, do so in accordance with local regulations.

Specifications

Supply voltage: Supply protection: Supply connection: 8 V to 30 V dc, protected against reversed polarity. 0.5 A fuse Minimum requirement either: 24 AWG single-strand wire. or 7/0.2 multi-strand wire. 70 mA maximum, with fully loaded talker ports. 4 x NMEA-183, galvanically isolated. >800 Ohm. 1 x NMEA-183. 2 buffers of 1000 characters (NMEA In 3 and NMEA In 4 only). Combined data from NMEA inputs. 4800 baud. 4800 baud. Overflow and Data LEDs. 138 x 72 x 33 mm. Flame retardant ABS.
Current consumption: Inputs: Input resistance: Outputs: Buffers: NMEA Out: Speed NMEA in: Speed NMEA out: Indicators: Dimensions: Housing:
Raymarine UK Ltd, Quay Point, Northarbour Road Portsmouth, Hampshire PO6 3TD, United Kingdom. Tel: +44 (0) 3611 Fax: +44 (0) 4642 www.raymarine.com
Raymarine Inc, 22 Cotton Road, Unit D, Nashua, New Hampshire 03063-4219, USA. Tel: +1 603.881.5200 Fax: +1 603.864.4756 www.raymarine.com

Brookhouse NMEA Multiplexer model AIS-C
This model Brookhouse multiplexer has been designed specifically for use with the popular Raymarine C-series displays. No other multiplexer or interface available today offers the same degree of integration of C-series displays with other instruments. It allows simultaneous connection of an AIS receiver*, fast heading sensor, DSC radio and other NMEA-compatible marine instruments to the single NMEA input port of the C-series display. In addition, the new multiplexer model accepts the NMEA output of the C-series and performs speed conversion as well as NMEA protocol conversion, if necessary, to enable

General

connection of NMEA listeners such as an auto pilot, a DSC radio etc. Installation of this multiplexer model is simple, no setup or configuration is necessary. The Brookhouse AIS-C multiplexer has 4 opto-isolated NMEA input ports, 2 NMEA (RS422) output ports, one RS232 output, one RS232 input, optional USB. For some time Brookhouse NMEA multiplexers have been the popular choice for connecting multiple NMEA compatible instruments, including AIS, to C-series displays (C60, C80, C120). Based on the experience with typical installations and some issues surrounding C-series compatibility with other instruments, this new
model NMEA multiplexer was developed to take seamless integration a step further. Raymarine C-series products support AIS. For AIS receiver connection to the NMEA input port high-speed communication of 38400bps is required. The NMEA input port of the C-series can be configured for this baud rate. Before the new multiplexer model AIS-C was available, the standard Brookhouse multiplexer with high speed port option was already suitable for combined input of high speed AIS* and other NMEA instrument data at standard baudrate and this product has found many satisfied users. However, activating AIS on the C-series has the side-effect that the NMEA output is rendered unusable. The new model AIS-C multiplexer offers a solution for this problem. Read about it below. Setting the baud rate of the NMEA input port of the C-series to 38400 for AIS, also affects the NMEA output port baudrate, which is set to 38400 at the same time. This high baudrate makes it impossible to directly connect instruments with standard 4800 baud NMEA input ports. The problem has been resolved by adding speed-conversion to the Brookhouse multiplexer. The C-series 38400 baud output can now be connected to a 38400baud NMEA input port on the multiplexer and the data stream is available at 4800 baud on another NMEA output port. Multiple standard NMEA listeners can be connected to this port. The speed-conversion is a separate, independent function in the multiplexer. The features of the Raymarine C-series products have made it an attractive option for installation on boats with existing instruments and (non-Raymarine) auto pilots. The C-
series output NMEA version 3.01 auto pilot control data (APB sentence). However, the NMEA version accepted by many auto pilots is 2.1 or older. The result is that the newer data-format is not recognised and these auto pilots do not function with the C-series equipment. Therefore speed-conversion is not always enough to drive standard NMEA auto pilots from the C-series. The Brookhouse multiplexer model AIS-C has a unique feature that adapts the NMEA data from the C-series to a format recognised by the auto pilot, if required. The script to perform the conversion can be pre-loaded in the multiplexer or loaded by the user in the field. Seatalk instrument and GPS data on the Seatalk-bus is converted to NMEA by the Cseries and is also available via the NMEA out port. This data can be used to feed a DSC radio, repeater instruments, etc. Potentially NMEA compatibility problems may surface here as well. Again, these problems can be ironed out in an elegant way by the Brookhouse multiplexer. Many existing scripts are available from Brookhouse that can be loaded into the multiplexer in a simple way by the user, to perform conversions and adaptions of the data. Redundant NMEA data can be filtered out, if necessary. For the more technically oriented users, details are available in the Brookhouse document NMEA data manipulation and filtering Raymarine recommend using a fast heading sensor to improve the performance of Marpa. Connection to the C-series display is via the NMEA port. The refresh-rate of headinginformation is 10Hz. This means that 10 NMEA sentences with heading information per second are transmitted. Combining this high intensity data stream with AIS and other

Other NMEA compatibility

NMEA speed conversion

Fast heading sensor

Auto pilot NMEA compatibility
NMEA equipment via the Brookhouse multiplexer presents no problems. The majority of C-series display installations use a Seatalk GPS receiver. Users are increasingly aware of the dependancy on this single GPS. It is often mounted in a vulnerable position where it can easily receive physical damage. The prudent skipper will install a spare NMEA GPS as backup, preferably below-decks. The Brookhouse NMEA multiplexer provides enough input ports to connect this extra GPS together with AIS and other NMEA talkers to the C-series display. For C-series installations without AIS, but with a fast heading sensor, the high baudrate setting of 38400 is still preferable, as this ensures sufficient bandwidth for the dataintensive heading sensor plus other NMEA talkers. The Brookhouse multiplexer model AIS-C is still the recommended choice in this case, because of the speed-conversion and other features. As a chart plotter, the C-series offer all navigation options that one can desire. However, the display is often mounted outside at the steering position and on many boats we find a (laptop) computer at the navstation below-decks, which can be used as a back-up, for route planning, tracking etc. The Brookhouse NMEA multiplexer AIS-C has a RS232 port for output of the combined data stream to a computer. A USB port is available as an option.

NMEA GPS

Although the features offered by the Brookhouse multiplexer model AIS-C suit the Raymarine C-series displays very well, it is also suitable for many other purposes. The multiplexer can be reconfigured by the user, if required and the baud-rate conversion can be switched off. The same features are available as in the standard NMEA multiplexer, including filtering.

Other installations

Specifications
4 opto-isolated NMEA Listener (Input) ports. 1 Output RS232 port (typically for connection to computer) 1 Input RS232 port. 2 Output RS422 ports (differential NMEA talker port) Data speed: 3 Input ports @ 4800bps (standard NMEA speed), 1 input port @ 38400 bps, RS232 Output port: 4800/9600/19200/38400 bps selectable in setup mode, default 38400 bps. Speed conversion 38400bps-4800bps. Indicators: red LED for power, green LED for data-transmission. Supply Voltage: DC 9-35 Volts. Reversed polarity protection. Power Consumption: 45 mAmps. @ 12V (with all ports active) Physical size: 110x65x37mm (hxwxd) Weight: 120 grams Mounting: bulkhead mounting with screws. NMEA management and control: o NMEA Sentence Filtering o NMEA Sentence editing on the fly for NMEA protocol conversion. o Automatic port switching (mainly for GPS backup) o Data pacing Options: o Raymarine Seatalk support. o USB for computer connection.

Installations without AIS

Computers

*All popular AIS receivers are supported, including NASA.

www.brookhouseonline.com