FF-Automation WSN169, WSN170, WSN225, WSN450, WSN470 Setup, Installation & Operating Manual

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WSN SERIES

RADIO MODEMS

SETUP, INSTALLATION

OPERATING MANUAL

WSN Manual Page 1 of 34 Rev. G – 4 March 2007

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CONTENTS

1 INTRODUCTION ..................................................................................... 3

1.1 PRODUCTS COVERED .................................................................................................... 3

1.2 IMPORTANT NOTICES ..................................................................................................... 3

2 PRODUCT OVERVIEW .......................................................................... 4

2.1 GENERAL .......................................................................................................................... 4

2.2 TRANSMITTER .................................................................................................................. 4

2.3 RECEIVER ......................................................................................................................... 4

2.4 MPU CONTROL ................................................................................................................. 5

2.5 PROGRAMMING & CONFIGURATION ............................................................................. 5

2.6 SOFT MODEM: .................................................................................................................. 5

2.7 MODES OF OPERATION .................................................................................................. 5

2.8 HANDSHAKING ................................................................................................................. 5

2.9 ADDITIONAL FEATURES ................................................................................................. 5

3 SPECIFICATIONS .................................................................................. 7

3.1 TECHNICAL SPECIFICATIONS ........................................................................................ 7

3.2 APPROVALS AND LICENSING ......................................................................................... 9

4 PRE-PROGRAMMED CHANNEL PLANS ........................................... 10

4.1 UK MPT1411/VNS2111 CHANNELS .............................................................................. 10

4.2 UK MPT1329 CHANNELS ............................................................................................... 12

5 SETUP & INTERFACING ..................................................................... 13

5.1 INTERNAL CONSTRUCTION.......................................................................................... 13

5.2 INTERFACE PORT PIN CONNECTIONS ....................................................................... 13

5.3 12VDC POWER ............................................................................................................... 15

5.4 ANTENNA PORT ............................................................................................................. 15

5.5 CHANNEL SWITCHES .................................................................................................... 15

5.6 PROGRAMMING ............................................................................................................. 15

5.7 RF POWER ...................................................................................................................... 15

5.8 TIME-OUT-TIMER ........................................................................................................... 15

5.9 INTERNAL MODEM ......................................................................................................... 16

5.10 RADIO DATA FORMATS ................................................................................................. 16

5.11 FORWARD ERROR CORRECTOR ................................................................................. 17

5.12 SQUELCH TAIL (DRIBBLE BITS) ELIMINATION ............................................................ 17

5.13 SERIAL INTERFACE & HANDSHAKING ........................................................................ 17

5.14 TRAFFIC PROTOCOL & ROUTING MODES .................................................................. 19

5.15 TRANSMIT & RECEIVE TIMING ..................................................................................... 20

5.16 POWER CONSUMPTION ................................................................................................ 23

5.17 POWER SAVE MODE ..................................................................................................... 23

5.18 “RSSI” RECEIVE SIGNAL STRENGTH INDICATION ..................................................... 23

5.19 STATUS LEDS................................................................................................................. 24

6 STORE & FORWARD........................................................................... 25

6.1 STORE & FORWARD BASED ON CLIENT PROTOCOL. ............................................... 25

6.2 MODBUS ......................................................................................................................... 25

6.3 RFT ROUTING PROTOCOL............................................................................................ 27

7 INSTALLATION .................................................................................... 30

7.1 INTRODUCTION .............................................................................................................. 30

7.2 POWER SUPPLIES ......................................................................................................... 30

7.3 EFFECTIVE RADIATED POWER (ERP) ......................................................................... 30

7.4 ANTENNAS, COAX FEEDERS & PERIPHERALS .......................................................... 31

7.5 MOUNTING & INSTALLATION ........................................................................................ 33

7.6 FIXING DETAILS ............................................................................................................. 33

WSN Manual Page 2 of 34 Rev. G – 4 March 2007

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1 INTRODUCTION

1.1 PRODUCTS COVERED

This manual covers the WSN Series of low cost, high performance radio modems designed for data applications in commercial and industrial systems.

The WSN is an advanced, simplex/half-duplex, data radio for transmission of serial data. Versions are available with three different serial port configurations:-

A true RS232 interface full handshaking. As above but with 5V TTL voltage levels on the interface rather than RS232 levels. An RS232/RS422/RS485 interface with software selection of required mode. (RTS/CTS

and DSR/DTR Handshaking lines looped back to each other in RS232 mode)

Information is provided to assist with configuration, installation, and operation of the products in point to point or point to multi-point applications. A separate programming manual covers the use of the associated WinA4P software for programming and configuration of the radios.

Component level servicing is not covered in this document; if the product fails its first line testing it should be returned to a service centre.

1.2 IMPORTANT NOTICES

1.2.1 Copyright

All rights to this manual are the sole property of FF-Automation Oy The copying of the manual in whole or in part by any method without written permission is strictly prohibited.

1.2.2 Right To Change

In the interest of improvement, R.F. Technologies reserves the right to change the technical specifications or functions of its product without notice.

1.2.3 Software

FF-Automation Oy software is delivered “as is”. FF-Automation Oy does not grant any kind of warranty or guarantees on its saleability or it’s suitability for use in specific applications.

Under no circumstances is R.F. Technologies liable for any damages arising from using the software. The copyrights relating to all software is the sole property of FF-Automation Oy. Any coping, editing, translating or modifying is strictly forbidden without prior written consent from FF-Automation Oy.

1.2.4 Safety Critical Applications

The WSN has not been designed for, nor is it intended for, use in safety critical or life support applications. No functional warranty is given if the product is used in such applications.

1.2.5 Use

The WSN radio modems have been designed to work on various licensed and license-free frequency bands in use around the world. In the license-free bands, the user must ensure that the radio modem is used under the terms & conditions applicable to the use of the bands concerned. In licensed bands, the user must obtain permission and the necessary licenses from the relevant authorities.

WSN Manual Page 3 of 34 Rev. G – 4 March 2007

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2 PRODUCT OVERVIEW

2.1 GENERAL

The WSN Series has been designed as a range of high specification, low cost radio modems for stand-alone applications or for integration into OEM products.

Through the use of advanced DSP technology, the design has been optimised for reliability and low current consumption, making the WSN suitable for operation on remote sites without mains power.

Applications include security, command & control, data logging, SCADA, telemetry, remote switching or any similar applications where serial data needs to be transmitted.

The WSN is available with three different serial interfaces:-

An RS232 interface with all signalling lines to allow full handshaking if required. A TTL version of the unit, which uses 5V TTL voltage, levels on the serial interface

connector rather than RS232 signalling levels, but is otherwise the same.

A version with an RS232/RS422/RS485 interface. Required interface mode is selected

using the configuration software. In RS232 mode, the RTS line is looped back to CTS and the DSR line is looped back to DSR. RS422/RS485 half-duplex (2-wire) or full duplex (4-wire) modes are both supported.

The data rate on the serial interface can set to a range of values from 150 baud to 38,400 baud, while the over-air data rate can be independently set to a range of values between 150 baud and 9,600 baud. If high throughput speeds are not required, the modem can be set to a slower over-air rate to take advantage of the associated improvement in receiver threshold.

The WSN is available with two different transmit powers. The low power version meets the licence-exempt ETS300-220 specification while the higher power 5W version meets the tougher ETS300-113 and the USA and Canadian specifications.

2.2 TRANSMITTER

The transmitter frequency can be user programmed anywhere within it’s pre-aligned bandwidth. There are two power versions available, 10mW to 750mW and 50mW to 5W. The transmit power of any particular hardware version can be set accurately within the relevant range under software control.

2.3 RECEIVER

The receiver is a very low current double conversion superheterodyne with an active balanced mixer for very good intermodulation performance. Careful attention to spurious response, adjacent channel and blocking performance, makes the product ideal for crowded telemetry channels. To achieve high performance the programmable bandwidth of the receiver has been limited (for UHF it is 10MHz, + 5MHz from centre frequency), full details are in the technical specification section. Should re-alignment be required, the unit can be returned to our service centre.

WSN Manual Page 4 of 34 Rev. G – 4 March 2007

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2.4 MPU CONTROL

The Microprocessor (MPU) is the heart of the product and at the centre is a 128k flash microprocessor that controls all the interface circuits to the radio module and external input/outputs. As well as the control function, the processor provides DSP functionality that enables modem operation between 150 and 9,600bps. The processor has 128k of flash memory from which the code is executed and internal EEPROM for storing programmed parameters.

2.5 PROGRAMMING & CONFIGURATION

The parameters of the WSN are PC programmable via the serial port. Full details of all the programmable parameters are covered in the separate programming manual. Details of cables and adaptors needed for the various interface versions are given in Section 5.6.

2.6 SOFT MODEM:

The WSN has a “soft modem” which allows over-air transmission at rates between 150bps and 9,600bps using a range of different modulation schemes. The over-air rate can be selected by the operator to optimise link performance.

2.7 MODES OF OPERATION

2.7.1 Transparent Operation

The WSN can operate transparently without packetising the data and without adding any other overheads, thereby maximising data throughput rates. It requires no knowledge of the data it is transmitting. Data is simply transmitted and received with minimal delay.

2.7.2 Protocol specific modem

The radio recognises a complete frame and only transmits and receives data conforming to that format. No addressing of radios or routing of data is performed. Protocols such as MODBUS & DNP3 can be supported in this way.

2.7.3 Routing modem

The radios recognise a protocol specific frame and the address to which the frame is to be sent. Routing information must be stored in each radio for each destination address that requires the use of repeaters. Any radio in the system can operate as a repeater. The radio does not perform any acknowledgement or retries. Any protocol using a fixed address field such as MODBUS can be supported.

2.8 HANDSHAKING

On the RS232 Full Handshaking and TTL versions, transmission control can either use RTS control signals or be configured for automatic initiation of transmission on receipt of serial data at the traffic interface. In either case, the radio provides a CTS output, which can optionally be used for flow control.

On the RS232/RS422/RS485 version, transmission is automatic when transmit data is applied. The DSR line is internally looped back to DSR and, when configured for RS232 mode, the RTS line is also looped back to CTS.

In all versions, the radio incorporates a 1,024 byte internal buffer to cope with situations where the interface data rate is higher than the over-air rate.

2.9 ADDITIONAL FEATURES

The WSN incorporates the following additional features which enhance the usability of the product and assist with the operation and maintenance of systems using the product:-

2.9.1 Status LEDs:

The WSN Radio Modems have a number of front panel LED’s to enable the operator to see at a

WSN Manual Page 5 of 34 Rev. G – 4 March 2007

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glance the status of the product and the serial data port.

2.9.2 Time-out Timer

The transmitter within the WSN has a user programmable time-out timer which allows the maximum continuous transmission time to be set in order to prevent channel blocking due to a fault.

2.9.3 Power-Save Modes

The WSN has both internally controlled and externally controlled power-save modes to reduce overall power consumption to extremely low levels for operation on sites without mains power.

2.9.4 Squelch Tail Elimination

As a user programmable option, the WSN can also operate in a packetisation mode where framing characters are added at the start and end of the user's message prior to transmission and stripped off again at the receive end prior to passing the user data to the interface connector. This can be useful in getting rid of any spurious characters which may otherwise be generated at the end of messages by squelch noise as the receiver mutes and which can affect old or non-tolerant protocols. In a high interference environment, enabling packetisation will often help to block reception of the interfering signals.

2.9.5 Forward Error Correction

The WSN allows an optional forward error correction to be switched in when the over-air data rate is 9,600bps. This will improve error performance, but there is an associated data throughput overhead of around 30%, which therefore reduces the effective transmission rate for the user data. The forward error corrector is not available at lower data rates, as it offers no significant performance enhancement at these lower rates.

WSN Manual Page 6 of 34 Rev. G – 4 March 2007

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3 SPECIFICATIONS

3.1 TECHNICAL SPECIFICATIONS

3.1.1 General

Frequency Range: WSN169/170 138 - 175MHz WSN225 175 - 225MHz WSN450/470 406 - 512MHz WSN869 869 - 870MHz (50MHz – 950MHz to special order)

Power Requirements: 12VDC (10V – 15.5DC) Standby: <75uA Receiver on & decoding: <70mA Transmitting: 300mA to 2.1A dependent on Tx power

Number of Channels: 80 sequential or 32 discrete user programmable channels. Min. Programmable

Channel Step: 6.25kHz or 5kHz Channel Spacing: 12.5kHz, 20kHz or 25kHz Operating Temp.

Stability: 2ppm –30 to +60ºC Construction: Aluminium enclosure. Size: 75mm W x 130mm L x 30mm H (excluding brackets and connectors) Mounting: Screws to a flat surface. Weight: 250g Connectors: DC Power 2-way Klippon Type

Serial Data 9-way D-Type Female RF BNC (50 ohm)

LED Indicators: TX, Busy, System, RXD, TXD

3.1.2 Transmitter:

RF Output Power: WSN 169/450/869 10mW - 750mW WSN 170/225/470 50mW - 5Watts

Bandwidth: VHF 10MHz without re-alignment UHF 12MHz without re-alignment 869 30MHz without re-alignment

Internal Modulation: Programmable for FFSK, 2-Level FSK, GMSK or 4-Level FSK. Max. Deviation: ± 7.5kHz max Duty Cycle up to 70% Adj. Channel Power: >65dB at 12.5kHz Spurious Emissions: As per ETS300-113 Rise Time: < 9mS

3.1.3 Receiver

Sensitivity: 0.25uV (-119dBm) for 12dB SINAD de-emphasised

0.355uV (-117dBm) for 12dB SINAD flat Bandwidth: VHF 5MHz without re-alignment

UHF 10MHz without re-alignment

WSN Manual Page 7 of 34 Rev. G – 4 March 2007

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869 20MHz without re-alignment Spurious Response: WSN 169/450/869 >65dB

WSN 170/225/470 >70dB Blocking: WSN 169/450/869 >85dBuV

WSN 170/225/470 >90dBuV Intermodulation: WSN 169/450/869 >60dB (3 Signal)

WSN 170/225/470 >65dB (3 Signal) Adjacent Channel: >65dB at 12.5kHz IF Frequencies: 45MHz and 455kHz Spurious Emissions: WSN 169/450/869 <ETS 300-220

WSN 170/225/470 <ETS 300-113 Mute Response Time: <2msec

3.1.4 Internal Modem

Serial Comms: Asynchronous (or Synchronous with custom software). Baud rate programmable between 150bps and 38,400bps

Interface: /232Full version :- RS.232 complete with signalling lines /TTL version:- 5V TTL levels rather than RS.232 /232+485 version:- RS.422/RS.485 (2 or 4 wire) or RS232 with looped back signalling lines.

Parity: Programmable as Odd, Even or None NRZI: On or Off Stop bits: Programmable 1 or 2 Data Bits: Programmable 7 or 8 Signalling Formats: Programmable as V23, Bell202 or MPT1327, up to 1200 baud, coherent

Synchronous/Async. Programmable as either up to 1200bps, synchronous above 1200bps Over-air Baud Rate: 150 – 9600bps within 12.5kHz Bit Error Rate: 150 - 2400 baud less than 1 x 10-3 at –120dBm

4800 baud less than 1 x 10-3 at –117dBm 9600 baud less than 1 x 10-3 at –115dBm (FEC on) 9600 baud less than 1 x 10-3 at –112dBm (FEC off)

Forward Error Corrector (FEC) is a programmable option at 9600bps. The bit error rates quoted above are for fixed messages representing

FFSK at 2400 baud, GMSK at 4800 baud, 4 Level FSK at 9600 baud.

typical data sent over the link. The BER should not be directly compared with other manufactures figures unless the data format is known, as many manufacturers quote a BER based on a simple alternating data pattern, which will generally give much better BER results.

WSN Manual Page 8 of 34 Rev. G – 4 March 2007

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3.2 APPROVALS AND LICENSING

The WSN has been designed to meet the relevant standards outlined below. Should others be required, please contact the sales office.

3.2.1 UK Approvals

MPT1411/VNS2111: The 5W version of the WSN has been tested to MPT1411 and the

replacement VNS2111 for licensed applications with a maximum data rate of 9600bps within a 12.5 kHz channel. A licence is required and the

permitted output power is normally stated on the licence. MPT1329: The radios meet the requirements of MPT1329 BS2011: The unit complies with the Vibration specification BS2011.

3.2.2 European Approvals

ETS 300-220 The unit meets the specification for European licensed exempt

communications with a maximum RF power level of 500mW. Please

note the permitted power level may vary from country to country. ETS 300-113 The 5W version of the unit meets the specification for licensed data

radios ETS 301-489: The unit meets the required CE specification and carries a CE Mark. EN60950 The unit meets the relevant requirements of this Safety specification.

3.2.3 European Declaration of Conformance

Hereby, FF-Automation Oy declares that the WSN Series of Radio Modems is in compliance with the essential requirements and other relevant provisions of Directive 1999/5/EC.

In the interest of improvement the above specifications are subject to change without notice.

WSN Manual Page 9 of 34 Rev. G – 4 March 2007

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4 PRE-PROGRAMMED

CHANNEL

SCANNER

OUTSTATIONS

457.50625

463.00625

457.51875

463.01875

457.53125

463.03125

457.54375

463.04375

457.55625

463.05625

457.56875

463.06875

457.58125

463.08125

457.59375

463.09375

457.60625

463.10625

457.61875

463.11875

457.63125

463.13125

457.64375

463.14375

457.65625

463.15625

457.66875

463.16875

457.68125

463.18125

457.69375

463.19375

457.70625

463.20625

457.71875

463.21875

457.73125

463.23125

457.74375

463.24375

457.75625

463.25625

457.76875

463.26875

457.78125

463.28125

457.79375

463.29375

457.80625

463.30625

457.81875

463.31875

457.83125

463.33125

457.84375

463.34375

457.85625

463.35625

457.86875

463.36875

457.88125

463.38125

457.89375

463.39375

457.90625

463.40625

457.91875

463.41875

457.93125

463.43125

457.94375

463.44375

457.95625

463.45625

457.96875

463.46875

457.98125

463.48125

457.99375

463.49375

458.00625

463.50625

458.01875

463.51875

458.03125

463.53125

458.04375

463.54375

CHANNEL PLANS

Using the PC configuration software, the WSN can be programmed with a number of standard channel plans. These currently include all UK MPT1411 or MPT1329 channels. Further standard channel plans may become available in later releases of the configuration software. A mixture of channels from different channel plans can also be entered discretely using the software.

The following tables show the channel numbers and associated frequencies for various channel plans:-

4.1 UK MPT1411/VNS2111 CHANNELS

WSN Manual Page 10 of 34 Rev. G – 4 March 2007

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458.05625

463.55625

458.06875

463.56875

458.08125

463.58125

458.09375

463.59375

458.10625

463.60625

458.11875

463.61875

458.13125

463.63125

458.14375

463.64375

458.15625

463.65625

458.16875

463.66875

458.18125

463.68125

458.19375

463.69375

458.20625

463.70625

458.21875

463.71875

458.23125

463.73125

458.24375

463.74375

458.25625

463.75625

458.26875

463.76875

458.28125

463.78125

458.29375

463.79375

458.30625

463.80625

458.31875

463.81875

458.33125

463.83125

458.34375

463.84375

458.35625

463.85625

458.36875

463.86875

458.38125

463.88125

458.39375

463.89375

458.40625

463.90625

458.41875

463.91875

458.43125

463.93125

458.44375

463.94375

458.45625

463.95625

458.46875

463.96875

458.48125

463.98125

458.49375

463.99375

WSN Manual Page 11 of 34 Rev. G – 4 March 2007

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CHANNEL

FREQUENCY

458.5000 Guard Ch.

458.5125

458.5250

458.5375

458.5500

458.5625

458.5750

458.5875

458.6000

458.6125

458.6250

458.6375

458.6500

458.6625

458.6750

458.6875

458.7000

458.7125

458.7250

458.7375

458.7500

458.7625

458.7750

458.7875

458.8000

458.8125

458.8250 Not Used

458.8375 Not Used

458.8500

458.8625

458.8750

458.8875

458.9000 Not Used

458.9125

458.9250

458.9375

458.9500 Guard Ch.

4.2 UK MPT1329 CHANNELS

The WSN can be programmed to operate on the full MPT1329 band of channels with access to channels 26, 27 & 32 denied, in line with MPT1329 band plan. The radio should be programmed for a maximum power level of 500mW.

WSN Manual Page 12 of 34 Rev. G – 4 March 2007

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1. DCD: Data Carrier Detect - - - o

2. RXD: Receive Data - - - - - - -

o- - - - - 6. DSR: Data Set Ready

o- - - - - 7.

3. o- - - - - 8.

4. DTR: Data Terminal Ready - - o o- - - - - 9. nc Not Connected

RTS: Request to Send

TXD: Transmit Data - - - - - - - o

CTS: Clear to Send

GND: GROUND - - - - - - - - - - o

5 SETUP & INTERFACING

5.1 INTERNAL CONSTRUCTION

The exploded view shows the main components of the radio modem. There are no user adjustments or settings, which require removal of the covers.

5.2 INTERFACE PORT PIN CONNECTIONS

The WSN Series is equipped with a 9 way female D connector for the traffic interface. The pins of this connector are allocated as follows:-

5.2.1 RS232-Only (Full Handshaking) and 5V TTL versions

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5.2.2 RS232/RS422/RS485 Versions

o- - - - - 9. nc Not Connected

o- - - - - 8. CTS: Clear to Send (Internally connected to Pin 7)

- - - - - 7. RTS: Request to Send o(Internally connected to Pin 8)

2. : Receive Data Output - - - - - - - - RXD o

o- - - - - 6. DSR: Data Set Ready (Internally connected to Pin 4)

o- - - - - 9. nc Not Connected

o- - - - - 8. *****: Do Not Use (Internally connected to Pin 7)

- - - - - 7. : -ve Data In to Radio

o TXD -

(Internally connected to Pin 8)

2. : -ve Data Out from radio - - - - - - RXD - o

o- - - - - 6. DSR: Data Set Ready (Internally connected to Pin 4)

The RS232/RS422/RS485 versions of the WSN may be software programmed to have either an RS232 or an RS422/RS485 compatible interface.

To allow programming without an interface adapter, a radio programmed for RS422/RS485 operation will switch back to RS232 operation if the front panel rotary switches are set to position 00 to select programming mode. Note that although the WSN can withstand RS232 voltages on its inputs in RS422/RS485 mode, this may not be the case for externally connected devices. To avoid any risk of damage to the externally connected equipment, care must therefore be taken to ensure that programming mode is not selected while connected to RS422/RS485 terminal equipment.

Pin allocation when set for RS232 operation:-

Pin allocation when set for RS422/RS485 operation:-

When half-duplex (2-wire) RS422/RS485 operation is programmed, the TXD- and TXD+ signals are internally connected to the RXD- and RXD+ signals respectively. The 2-wire half-duplex bus only needs to be connected to the RXD- and RXD+ pins (Pins 1 and 2). Shorting links are not required in the connector.

When operating in 2-wire RS422/RS485 mode, the radio will output data on to a 2 wire circuit whenever it is received, which could lead to a bus conflict in conditions of high interference and prevent a connected terminal from outputting transmit data. To avoid this condition it is recommended that the message packeting option is turned on at both ends of the radio link.

The DTR and DSR signals are looped back to each other internally in both configurations. When configured for RS232 operation, the RTS and CTS signals are also looped back to each other. The radio should in most circumstances operate correctly in applications requiring RTS/CTS handshake although the it is unable to use CTS to prevent buffer overflow. Overflow situations can easily be avoided by making the serial port baud rate the same as the radio signal baud rate, or by ensuring that message sizes do not exceed the buffer size of 1024 bytes.

The DTR input has a threshold of approximately +1.5V with respect to ground, it may be used with a standard RS232 level signal or a TTL level signal in either RS232 or RS485 mode, the signal is active high in both cases.

WSN Manual Page 14 of 34 Rev. G – 4 March 2007

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5.3 12VDC POWER

A nominal 12VDC (9.6 – 15.5Vdc) is supplied to the unit via a 2 way pluggable terminal block, the polarity is marked on the front panel and the plug has a polarity key to prevent accidental polarity reversal. In the event of a polarity diodes and fuses protect reversal the circuit board.

5.4 ANTENNA PORT

The antenna connection is a 50-ohm BNC connector. This should be connected to a suitable antenna or terminated in a 50-ohm load whenever the transmitter is activated. Transmission into an open circuit may cause excessive current to be drawn from the supply and damage could occur.

5.5 CHANNEL SWITCHES

The WSN can be user programmed with up to 80 sequential or 32 discrete simplex or semiduplex channels. The two front panel BCD switches select the required channels or, if both are set to zero, program mode is entered. In program mode, the radio interprets any signals on the serial interface as programming commands rather than data for transmission. When viewing a WSN with the aerial connector at the top, the left hand rotary switch is the "tens" switch and the right is the "units" switch, thus to set channel 37, set the left switch to 3 and the right to 7.

5.6 PROGRAMMING

The parameters of the WSN can be programmed via the serial port using either DOS or Windows based software. The individual configuration files can be stored on disc for future use or printed. Full details of all the programmable parameters are covered in the separate programming manual. The RS232 Only (Full Handshaking) version can be connected directly to the serial port on a PC using a straight-through cable. The 5V TTL version needs an adaptor unit between the WSN and the programming computer to convert between RS232 and TTL voltage levels. The RS232/RS422/RS485 version does not need an adaptor because the serial port switches to RS232 mode automatically when the radio is put into program mode by setting both front panel switches to zero. A standard straight-through cable with all pins connected may be used for connection to the PC.

5.7 RF POWER

The transmit power can be accurately set using a locally connected PC running the supplied configuration software. This allows the RF power level to be programmed directly in Watts or milliwatts with an accuracy of +/-1dB. There are no internal power adjustment points inside the modem. There are two transmit power ranges available. The low power WSN169, WSN450 & WSN869 versions can be set between 10mW and 750mW, while the higher power WSN170, WSN225 & WSN470 versions can be set between 50mW and 5W.

5.8 TIME-OUT-TIMER

The transmitter within the WSN has a time-out timer, which allows the maximum continuous transmission time to be set in order to prevent channel blocking due to a host fault. The timer works in all modes (external/internal modem) and is programmable in one-second steps between 0 and 255 seconds. If not required the timer can be programmed off. If the timer is enabled and the selected time is exceeded, transmission will cease until the action that normally causes transmission is removed and then re-applied. More explicitly, with RTC/CTS handshake enabled RTS must be dropped and then raised again, or if handshake is not enabled character transmission must be suspended for at least two character periods at the serial port baud rate. In all modes the modem’s SYS led is flashed at least twice when time-out occurs, the flashing continues while lockout is in force. The lockout timer is disabled if the

lockout time is set to 0. The lockout timer can be operated in “resettable” or “cumulative” mode,

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in resettable mode the timer restarts each time a transmission is made, in cumulative mode the timer counts up during transmit, and down during receive. If the timer counts up to the lockout time during transmit, lockout occurs; this will eventually happen if the radio spends more than half of its time transmitting. Lockout in this mode is indefinite and can only be reset by powering the radio off.

5.9 INTERNAL MODEM

The WSN features an internal “soft modem” which offers unparalleled performance and

flexibility over a wide range of speeds and formats. Data is presented to the modem via the RS232 (or TTL) serial connection at speeds between 150 and 38400 and then transmitted at the programmed radio baud rate. Buffering is provided when the data rate is higher than the radio transmission rate.

5.9.1 Modulation & Tone-sets

Within a 12.5kHz channel, the over-air transmission from the unit can be programmed for a range of speeds. For 150, 300, 600,1200, the modulation is FFSK with Bell 202 and V.23 (Mode 2) tone-sets both supported. At these lower speeds, it is also possible to select a protocol specific MPT1327 mode, which uses a 1200/1800Hz tone-set to allow compatibility with number of additional modems from other manufacturers. At 2400bps the modulation is coherent FFSK, at 4800bps it is GMSK and at 9600bps it is 4-Level FSK. If operating at speeds up to and including 1200bps and compatibility with other equipment is not required, the use of the Bell 202 tone-set is recommended, as this will give the best link performance.

5.9.2 Synchronous/Asynchronous Modem Operation

The radio modem can be programmed for asynchronous or synchronous operation at baud rates up to 1200. At baud rates of 2400 or more, modem operation may only be synchronous. This relates to the over-air signal and has no bearing on the format of the data presented at the serial interface port

In synchronous mode inverted NRZI encoding is used where a one is represented by a transition in the binary data, every transmitted bit fits into a time slot defined by the baud rate, this allows a phase locked loop to lock on to the data stream to give better performance in noisy conditions, the inverted NRZI encoding allows this to continue even when the signal is idling sending stop bits. The inverted NRZI encoding gives a further advantage with GMSK signalling since the polarity of the signal is unimportant.

In asynchronous mode NRZ encoding is used where a “one” tone represents a binary one, and

a “zero” tone a binary zero, whilst each character consists of bits of equal duration defined by

the baud rate, the time between the end of a stop bit and a following start bit may be arbitrary. This prevents the implementation of a phase locked loop to improve signal to noise performance but does allow use within older systems that do not implement synchronous transmission or NRZI encoding.

If compatibility with other radios is not required, the use of the synchronous mode is recommended, as this will give best link performance.

5.10 RADIO DATA FORMATS

The data rate over the air can be set up independently of the rate set for the serial interface, but the over-air rate should be set either at the same speed or a lower speed than the serial interface rate. The radio baud rate should be set at the minimum possible to maintain the required throughput, lower speeds will give better results in poor signal conditions

The radio signal can be set up to operate using 7 or 8 bit data, 1 or 2 stop bits, and odd, even or no parity. This setting is also independent of the serial port set up. This flexibility allows compatibility with other radios.

If the Forward Error Corrector is enabled (option only available at 9,600bps), the selected radio signal format is over-ridden as detailed below.

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5.11 FORWARD ERROR CORRECTOR

At 9600bps there is also a programmable option to switch in a forward error corrector. When switched on, the over-air data format changes to a fixed format using 14 bit words. These comprise 8 data bits, 5 CRC (Cyclic Redundancy Check) bits and a flag bit which is used to differentiate control and data functions in messages. An additional 14 bit synchronisation word is also sent after every 8 data words. The effect of this redundancy on a typical 9600bps link configuration is to reduce the effective data transfer rate to around 6300bps. The error corrector is aimed at improving performance in weak signal conditions, rather than recovering data in deep fades or burst-error conditions. An error rate of 1x10-4 with the FEC switched off will typically improve by a factor of 2000 to around 5 in 10-7 when it is switched on, but an initial error rate of 1x10-3 with it off will only improve by a factor of around 250 to something like 4x10-5 when it is switched on. In terms of receiver sensitivity, the 1x10-6 thresholds improve by around 0.4uV (or 6.4dB) when the FEC is switched on.

5.12 SQUELCH TAIL (DRIBBLE BITS) ELIMINATION

The WSN has an optional packetisation mode, which can be enabled using the configuration program. This adds framing characters at the start and end of the user’s message prior to transmission. The additional information is stripped off the messages at the receiver prior to passing the data to the interface connector. Packetisation can be useful in getting rid of any spurious characters which may otherwise be generated at the end of messages by squelch noise as the receiver mutes or by interference and which can affect old or non-tolerant protocols. It is important to note that packetisation must be set the same on all radios operating together. All radios must have it selected or all radios must have it de-selected.

5.13 SERIAL INTERFACE & HANDSHAKING

5.13.1 Handshaking on RS232/RS422/RS485 version

In this version of the WSN, transmission is automatic when transmit data is applied. When configured for RS232 mode, the RTS line is looped back to CTS and the DSR line is looped back to DSR. The radio should in most circumstances operate correctly in applications requiring RTS/CTS handshake although the it is unable to use CTS to prevent buffer overflow. Overflow situations can easily be avoided by making the serial port baud rate the same as the radio signal baud rate, or by ensuring that message sizes do not exceed the buffer size of 1024 bytes.

5.13.2 Handshaking on RS232-Only (Full Handshaking) and TTL versions

The RS232 Only (Full Handshaking) and TTL versions can be programmed either to use RTS/CTS handshaking to initiate transmission, or to transmit automatically whenever data is present at the serial input. In the latter mode CTS is still operated to implement flow control but can be ignored unless message sizes exceed 1k byte and the serial port baud rate is higher than the radio signal baud rate. These handshaking modes are compatible with modes A, C and D of the CMD400 manufactured by Pacscom Ltd.. Mode B (byte stuffing mode) is not supported.

Transmission Using RTS/CTS Handshaking (RS232-Only and TTL Versions):-

If handshaking is enabled, operating RTS starts transmission. CTS can then be monitored for flow control purposes. In the idle state CTS is inactive, but when RTS is operated CTS will become active immediately and data may be input to the serial port. When all data has been loaded to the serial port RTS should be dropped. Transmission will continue until all data in the serial input buffer has been sent, then CTS will become inactive and transmission will cease. During transmission the amount of data in the serial buffer is checked by the radio, if the buffer becomes ¾ full CTS is dropped to request the host to stop loading data, CTS is activated again when the buffer is reduced to ¼ full. To prevent timing problems data will still be accepted into the buffer when CTS is de-activated due to buffer filling during transmit, however any data received once CTS has dropped at the end of a transmission will be discarded, this prevents such data from being prefixed to the beginning of the next message.

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Transmission Without Hardware Handshaking (RS232-Only and TTL Versions):-

If RTS/CTS handshaking is disabled the radio will start transmission as soon as data is received at the serial port, transmission ceases as soon as the serial buffer has been emptied and a period equivalent to two characters at the radio signal baud rate has elapsed. It is important to note that since transmission ceases as soon as a two-character delay in the incoming data stream is seen, data characters in a message must be presented in a continuous back-to-back stream.

In this mode CTS is still used to indicate the serial buffer fill level in the same way as described in the section on transmission using handshake, the difference is that in the idle state CTS is always active indicating readiness to accept data. In most applications CTS can be ignored as messages are likely to be smaller than the serial input buffer (1k byte), bear in mind also that if the radio baud rate and data format is the same as that configured for the serial port the buffer is being emptied as fast as it is being filled and so buffer overrun is unlikely.

5.13.3 Data Reception

Any data received by the radio is simply output to the serial port, and in RS232 configurations the DCD line can be programmed to operate in three different modes to assist the host. Firstly by indicating that a carrier is detected on the radio channel, this is useful if a busy lockout function is required (although this can be dangerous if the channel is susceptible to interference as well as wanted signals), secondly DCD can indicate presence of a carrier and a valid data signal, data will normally be output under this circumstance, the third mode behaves in the same way as the second except that DCD remains active until all data has been output to the serial port after the signal has gone, this allows DCD to be used as a wake up signal. In RS422 and RS485 2-wire configurations, the radio will output data on to the 2 wire circuit whenever it is received, which could lead to a bus conflict in conditions of high interference, preventing any connected terminal from transmitting data when it wants to. To avoid this condition it is recommended that the message packeting option is turned on at both ends of the radio link in this mode.

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5.14 TRAFFIC PROTOCOL & ROUTING MODES

5.14.1 Transparent Mode

In this mode, the radio has no knowledge of the data it is transmitting, data is simply transmitted and received under hardware control with the option of RTS control or initiation of transmit after receiving serial data, with CTS providing an optional flow control. This configuration is useful when expanding older systems where the radios must be compatible with other manufacturers equipment.

5.14.2 Protocol Specific Mode

5.14.3 Routing Mode

The radios recognise a protocol specific frame and the address to which the frame is to be sent. Routing information must be stored in each radio for each destination address that requires the use of repeaters or store & forward nodes. Any radio in the system can operate as a repeater/store & forward node. The radio does not perform any acknowledgement or retries. Any protocol using a fixed address field such as MODBUS or RFT ROUTING can be supported.

5.14.4 STORE & FORWARD OPERATION

The WSN can support “Store & Forward” repeater operation to cope with situations where the

direct communication between sites is not possible due to range or terrain. The WSN series supports up to six repeaters within one link, although the more repeaters used, the greater the signal strength has to be at each receiver, as there will be some accumulative degradation over the whole link. The forwarding is carried out based on the Protocol Routing Mode and is based on the address fields within the data to be transmitted. At a repeater site, the incoming message is stored and then re-transmitted if it is for a protocol address further down that chain of radios.

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5.15 TRANSMIT & RECEIVE TIMING

The WSN only operates in a simplex or semi-duplex mode. In simplex mode the receive and transmit frequencies are the same, whereas in the semi-duplex mode they are different. In either mode data is only sent in one direction at a time as the radios do not have separate synthesisers for transmit and receive. If full duplex mode is required (transmit & receive at the same time) the ART product should be considered.

In simplex/semi-duplex mode, the radio synthesiser must be reloaded each time Receive or Transmit is selected. Although relatively short, the synthesiser loading time must be taken into account when looking at data transfer times.

In order to reduce adjacent channel interference in line with ETS300-113, the power output from the transmitter has finite rise and fall times, a distant receiving radio will therefore see an incoming signal later than a nearby one. The receiving radio also requires time for the carrier detect circuit to operate and for the modem to lock on to the incoming audio signal.

When using the WSN, there are a few timing considerations to be taken into account. The main

one is the programmable “lead in delay”, which is required for the modem to lock on to the

incoming data stream and is dependant on the radio signal baud rate. Minimum timings are given below:

Baud Rate Lead in Delay (Minimum) 150 80ms 300 60ms 600 40ms 1200 40ms 2400 40ms 4800 20ms 9600 30ms

For simplex/semi-duplex operation, time is required for the transmit and receiver synthesiser to be loaded and locked prior to transmission/reception. This timing constraint is important when deciding how soon after receiving a message a reply may be sent. For simplex/semi-duplex operation the WSN is ready to receive data approximately 25ms after transmission ceases. It is therefore necessary to either wait this length of time after receiving a message before sending a reply or to extend the lead in delay by the same amount to hold off transmission of the data.

For applications where power save is in use the lead in delay should be extended to allow the receiving device to wake up. The time required can be calculated by adding the save on time to the save off time and adding 10 percent, e.g. for a save on time setting of 800ms and a save off time of 200ms the lead in delay should be 1100ms. Care must be taken when replying to a previously transmitting WSN when RTS/CTS handshake is not being used, in this mode the transmitting device will wait for two character times before turning off its carrier and may therefore miss the beginning of a reply if it comes too soon, this may be overcome either by imposing an additional two character delay in the controlling device or by extending the lead in delay by that amount.

The WSN also has a facility for imposing a lead out delay, which is the time that the carrier remains on after transmission of the message is complete. This delay can normally be left at zero as it is only of use where a controller makes use of the DCD signal to suppress data processing but suffers some delay in processing received data, or where there is a need to delay any spurious squelch tail characters generated sufficiently that connected equipment does not confuse them with part of the message.

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5.15.1 Receive To Transmit Switching Time

Symbol

Description

Semiduplex

Simplex ttxon

Time from external action to commencing transmission

9ms

tlid

Duration of synchronisation transmission (lead in delay)

Table B

trbyte

Duration of 1 byte at radio signal baud rate

Table C

tmdel

Modem decode latency

Table D

Baud

150

300

600

1200

2400

4800

9600

Min tlid

80ms

60ms

40ms

20ms

30ms

Baud

150

300

600

1200

2400

4800

9600

trbyte

66.7ms

33.3ms

16.7ms

8.3ms

4.17ms

2.08ms

1.04ms

Baud

150

300

600

1200

2400

4800

9600

tmdel

6.9ms

3.5ms

1.7ms

1.3ms

1ms

When using the internal modem the action that initiates transmission can be either receipt of a character at the serial port or the operation of RTS. These examples use the first mode. The radio does nothing until the stop bit of the first character for transmission has been received, the transmitter is then started:

The time delay between receipt of the stop bit for the first character to be transmitted at the transmitting radio and output of the start bit of that character at the receiving radio is the sum of the values ttxon, tlid, trbyte, and tmdel shown in the diagram above. Values for these parameters are indicated below:

TABLE A: Timing values for duplex and simplex modes are as follows:

TABLE B: The lead in delay is a programmable parameter but minimum values dependant on baud rate must be adhered to. However, in a scanning system with the base station on continuous transmit the base station lead in delay can be set for Zero (thereby saving valuable time) as the internal outstation modems will always be synchronised.

TABLE C: The duration of a byte at the radio baud rate is dependant upon the data format employed, the table below assumes a format of one start bit, 8 data bits, no parity and 1 stop bit, i.e. a total of 10 bits per character. If another format is used the appropriate correction must be made.

TABLE D: The modem decodes latency takes into account delays introduced by hardware and software filters. The total delay is baud rate dependant:

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5.15.2 Message Duration

symbol

Description

value

thold

Period for which carrier is held up after sending last data byte

2.5ms + LOD

trxrdy

Time to reload transmit synthesiser in simplex mode

6ms

The time taken to transmit a message can be simply derived by multiplying the number of characters in a message by the values given in table C making any appropriate corrections for data format. The exception is 9600 baud where extra synchronisation sent during the message must be taken into account, 8 synchronisation bits lasting a total of 0.833ms are sent after every eighth message character.

5.15.3 Transmit To Receive Switching Time

In full or semi-duplex operation transmit to receive switching time does not need to be considered as the receive path is maintained during a transmission, in simplex operation some time must be allowed to reload the transmitter synthesiser to stop it from interfering with the receiver. The diagram below indicates the minimum time in which the radio is able to receive a signal after completing a transmission.

During the time thold the radio transmits some padding bits to allow for propagation delays in the receiving device before shutting off the carrier, this prevents possible chopping of the message tail. The time thold is composed of a fixed 2.5ms period plus the programmable value LOD (lead out delay). LOD is normally set to zero. After the time trxrdy has expired the radio is ready to receive a new signal.

N.B. If RTS/CTS handshaking is not used the transmitter is turned on whenever data is received at the serial port, the transmitter is left on until all buffered data has been transmitted and no data has been input for a time equivalent to the length of two characters at the radio baud rate (refer to table C). In general data transmitted by the radio is delayed with respect to its receipt at the serial port by the receive to transmit switching time, if the radio baud rate and serial port baud rate and both data formats are the same this delay remains constant throughout the transmission. At the higher baud rates this delay is generally greater than the length of two characters and so the procedure to stop transmission is started as soon as the last character has been sent, at the lower baud rates however it is possible that the time thold is extended while the radio waits for the two character timeout to expire, this can also happen if data characters are not loaded back to back into the serial port.

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5.16 POWER CONSUMPTION

TX Power

500mW

200mW

100mW

50mW

Max. Current

2.1A

1.8A

1.6A

1.3A

950mA

675mA

500mA

390mA

300mA

The WSN is a very low power product and is ideal for operation from batteries with solar power backup. The information below is intended to help the user decide on the best battery and solar cell size for operation at non-powered sites.

5.16.1 Transmitter RF power verses current

5.17 POWER SAVE MODE

The WSN is equipped with an internal and external power save mode. These are outlined below:

5.17.1 Internal Power Save

In this mode the microprocessor switches the transceiver off and after a pre-programmed time (Save on time) switches the unit back on (Save off time). If a carrier is not detected then the transceiver again switches off. If during the time the transceiver is awake a carrier is received, the unit will stay on. After the carrier drops out the receiver will stay on until the programmed resume time elapses. Once the resume time has elapsed the unit will return to its power save mode. The Save On/Off and Resume time are all programmable via the PC program. Obviously the amount of power saved increases with the programmed save on/off ratio, however with power save enabled long lead times must be programmed to wake up the unit before communication can take place. Therefore it may not be possible to run all applications under the power save mode due to the turn around times required by the host system. In some circumstances it is possible to achieve power save and fast polling: If polling of all outstations is carried out in cycles with a reasonable gap between each cycle, a long initial poll can be used to wake up all stations, the resume timer will then restart each time an outstation is polled allowing fast access, when the cycle is complete all stations will return to power save after the resume time has expired.

5.17.2 External Power Save

Under this mode the on/off ratio is controlled externally via the DTR line (DTR shut down must first be enabled using the set up program). In this mode more of the modem's circuits are shutdown (including the microprocessor), this saves more power but care must be taken to ensure that the modem is enabled when a transmission is to take place. Note that there is a hardware link option to allow the serial port to shut off when DTR is not active; this allows the radio current to be reduced to its bare minimum. In applications where DTR is not connected this link option must of course be disabled.

5.18 “RSSI” RECEIVE SIGNAL STRENGTH INDICATION

The WSN produces an internal DC signal, which is proportional to the received signal strength. The DC signal is passed to the internal MPU where it accurately measures its value by an internal A-D converter. The radios are individually calibrated during production so that signal strength can then be read in dB microvolts on a PC connected to the serial port.

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5.19 STATUS LEDS

The WSN has a number of LEDs to enable the operator to see at a glance the status of the product and the serial port:-

RX RF Carrier Detect/Busy TX Transmit SYS System RXD Receive Data TXD Transmit Data

5.19.1 System LED

With the Exception of the System LED the remainder are self-explanatory. The System LED lights when the radio is being programmed and is also used as a quick check as to the status of the unit. If any alarms are detected it will flash out an Error number.

5.19.2 Error Number

The modem reports errors in two ways, firstly the BUSY led will come on and the SYS led will flash a number of times, the BUSY led will then go out again and if the fault persists the procedure will be repeated. An error number can be determined by counting the number of times the SYS led flashes while the BUSY led is on.

ERROR No FAULT 1 Position of the channel switches has changed. 2 A channel has been loaded that has no RX frequency programmed. 3 Transmission has been attempted on a channel that has no TX frequency

programmed.

4 The receiver synthesiser phase locked loop has failed to lock due to bad

channel data or programming of an out range frequency.

5 The transmitter synthesiser phase locked loop has failed to lock due to

bad channel data or programming of an out range frequency.

6 The contents of the microprocessor's EEPROM are corrupted (failed

checksum) in the general program area. 7 Internal comms with a high power amplifier have failed. 8 The contents of the microprocessor's EEPROM are corrupted (failed

checksum) in the calibration area. 9 The contents of the microprocessor's EEPROM are corrupted (failed

checksum) in the factory program area. 10 No POCSAG message stored for repeat test. 11 Rotary channel switch position overridden by software. 12 Tx power setting out of range. 13 Packet Mode cycle pointer invalid. 14 Bad routing table area EEPROM checksum. 15 I2C Bus initialisation error.

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6 STORE & FORWARD

6.1 STORE & FORWARD BASED ON CLIENT PROTOCOL.

To conserve valuable air time and avoid the possibility of collisions due to coverage overlaps with other repeaters transmitting at the same time, only messages that require forwarding by specific repeaters are re-transmitted when the WSN is used in “Store & Forward” mode. Stripping out the addresses of incoming serial messages, comparing the address with the list of outstation addresses stored in the unit and routing the messages accordingly achieve this. This requires knowledge of the client’s message structure and, specifically, where the address can be found in the message. There is normally local communication at the store and forward site, via the RS232 port. We have written various store & forward drivers to cope with a number of client specific message formats and are always happy to write new drivers as and when required. Further information is available from the sales office.

6.2 MODBUS

6.2.1 Setting Up MODBUS Operation

The WSN can be programmed to transport “MODBUS ASCII” or “MODBUS RTU” format

messages in single master systems. These options are selected as the “INTERFACE

PROTOCOL” in the “EDIT MODE/INTERFACE” menu. It is not necessary for all radios to run the same Modbus interface, “MODBUS ASCII” and “MODBUS RTU” modes can be mixed within

a system.

When Modbus modes are enabled the “NETWORK ID” and “RADIO ADDRESS” fields must be

filled out such that every radio in a system has the same network ID, but a different radio address. Notes should be kept detailing the installation of radios and their addresses.

When transporting Modbus messages the master station radio must be programmed with a

routing table. This is accessed in the “EDIT MODEM/INTERFACE” menu by setting “ROUTING

TABLE” to “ON” and selecting “EDIT ROUTING TABLE”. This selection leads to several pages

of Modbus addresses and the route by which every Modbus address is reached must then be entered, for example if the Modbus device with address 37 is physically connected to the radio with radio address 23, and radio 23 is accessed from the base station via relay radios 4 and 19,

then the field entitled “MBUS 37” should be loaded with the route “4,19,23”. If the Modbus

devices with Modbus addresses 65 and 93 are physically connected to radio 45 and no relays are required then the fields entitled “MBUS 65” and “MBUS 93” should both be loaded with “45”.

6.2.2 MODBUS Operation

Operation in Modbus modes relies on the master/slave poll/reply nature of Modbus. The set up of the radios does not differentiate between a master and slave; the only difference in practice would be that the master station radio will be loaded with a routing table. There is no restriction on the number of masters in a system, but they should all be loaded with routing tables.

When a poll is initiated at a master station radio the destination Modbus address in the Modbus message is looked up in the routing table to determine the addresses of the radio(s) required to complete the link, the message is then sent and all the radios expect to send a reply back the same way. Once this reply has been sent the radios are all ready to start another poll/reply sequence.

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If a radio is specified as a relay in a link, any locally connected Modbus devices will not be aware of communications that take place as no activity occurs on the serial port in this state. This may cause problems however if more than one master exists in a system as a radio that is being used as a link in a relay is not available to transmit messages.

6.2.3 Power-Save Operation With MODBUS

When Modbus modes are enabled in the configuration programme two further fields appear

entitled “MIN PWR SAVE ADDRESS” and “MAX PWR SAVE ADDRESS”. If power save

operation is not required set both these fields to zero.

If power save operation is required it is enabled by setting the “RADIO ADDRESS” to a value greater or equal to “MIN PWR SAVE ADDRESS” and less than or equal to “MAX PWR SAVE ADDRESS”. The radio will then enter low power standby mode for the time programmed in the

“PSAVE ON TIME” field in the main edit menu, it will then wake up and check for an incoming

signal, if none is present it will return to sleep and repeat the cycle. If a signal is detected the radio will stay awake until a reply to the outward-bound message has been returned.

When the master station or relay radios send an outward bound message, the address of the radio to which the message is being sent is checked against the min and max power save addresses, if a power saved radio is indicated a cyclic wake up message is sent for the period indicated by the programmed power save on time before the actual data message is sent, if a power saved radio is not indicated the data message is sent immediately. These parameters along with some others are also used to calculate a timeout time in the event that no reply is received. It is therefore essential that all radios in a system are programmed with the same parameters even if not power saved, otherwise communications will fail.

Note that if “DTR SHUTDOWN” is enabled a radio remains completely shut down while DTR is

inactive, it will not wake up according to the power save timer to see if any incoming messages are present. This mode should therefore only be used in conjunction with real time message scheduling.

6.2.4 Serial Port Handshaking With MODBUS

When Modbus modes are enabled the DTR and DSR signalling lines can be used to assist in

power saving the host Modbus device. The RTS and CTS lines are not used and the “RTS/CTS HANDSHAKE” option in the “EDIT MODEM/INTERFACE” menu of the WinA4P programme

should be set to “OFF” in RS232 versions. When the Modbus slave is ready to accept data it

should assert DTR, DSR will be asserted in response and the received message will be output

to the Modbus device. The “HOST INACTIVITY TIME” field in the set up programme defines a

time limit for the Modbus device to assert DTR in response an incoming message and if this time limit is exceeded the radio sends back a reply indicating the destination device failed to respond and the link is cancelled. After sending a response, the Modbus slave may then release DTR and return to power save mode. Note that as long as DTR is asserted the radio will not return to its power save mode (if enabled in the setup programme). DSR will remain asserted in this case.

The master station can also control the power saving of its radio using DTR, the radio will operate in power save mode as long as DTR is not active, asserting DTR wakes the radio, DSR is asserted in return to indicate that the radio is awake and ready to accept data.

If use of the handshake lines is not required DTR should be connected to a voltage of +3.5 to +15V such that sleep mode is never allowed.

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6.2.5 Timeouts in MODBUS Modes

When a transmission from a master station radio is made in Modbus mode the radio will calculate a timeout for a reply, this calculation is based on many configuration parameters including the radio baud rate, lead in delay, host inactivity time, maximum message length, power save timing etc. If power saving is enabled and the baud rate is low this time can be large (the calculation limits the result to a maximum of 4.25 minutes. To reduce the possibility of “hung” radios the destination radio will send a link-closing message if the destination Modbus slave does not reply. This link-closing message is only used by the radios to close the link, it is not passed to the Modbus master.

If the Modbus master itself times out before the radio link does, it can send another poll, and radios along the link will cancel the previous route and set up the new one. The exception to this is the previous destination radio if it is still trying to wake up its Modbus slave, it will ignore the new message and try to download its original message when the slave awakes, a conflict will then arise if a reply is sent. To avoid this situation the Modbus master timeout time should allow

the maximum “HOST INACTIVITY TIME” to expire plus the time required to get a message and

its reply through the link.

6.3 RFT ROUTING PROTOCOL

6.3.1 Setting Up RFT Routing Operation

The WSN can be programmed to route non-specific protocol messages in single master

systems using “RFT ROUTING” mode. This mode supports relay messaging. This option is

selected as the “INTERFACE PROTOCOL” in the “EDIT MODEM/INTERFACE” menu.

In describing operation the address contained in the host system message will be referred to as

the “protocol address” and address programmed in the radio under the “RADIO ADDRESS”

field in the setup program will be referred to as the “radio address”.

RFT Routing mode is controlled at the master station by picking out an 8 bit protocol address field in the message to be sent, this address is then looked up in the routing table stored in the master station radio. The routing table can contain the radio address (as programmed in the RADIO ADDRESS field in the setup program) of a single radio connected to the required destination device or a list of relay radio addresses plus the destination radio address. The message is then transmitted from the base station radio as a packet with the routing information prefixed to it. The message is then relayed through any relay radios specified until it reaches the destination radio where it is output from the serial port in its original form with the packet information removed. During this process each radio considers itself to be part of an established link. A reply is then expected, however the outstation radios are not programmed with routing tables, a reply issued is assumed to be destined to the master station. The address in the protocol message is therefore not checked and the reply is simply sent back down the established link to the master station radio where it is output from the serial port. As the reply is passed back the link members no longer consider themselves to be part of an established link and return to idle.

Note that there is no differentiation in operating mode between a relay radio and an outstation radio, if an outstation radio is specified as a relay in a link any device connected to the local serial port will be unaware of relay communications taking place.

The packet used to transfer protocol messages specifies the route to be taken and also the

current stage in the route, it is therefore of no concern if radios further down a relay link “hear”

the message before they are expected to repeat it, they will ignore the message until specifically requested to repeat it.

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The position of the address in the protocol field is specified using the “ADDRESS OFFSET”

parameter in the setup programme. A setting of 0 specifies zero offset, i.e. the address is the first byte in the message, an offset of 6 specifies the 7th message byte and so on. 16 bit addressing or more is not supported as a maximum of only 256 destinations can be supported by the routing table. If the protocol message format does use 16 bit addressing specify the offset for the least significant byte and try to ensure that no two devices use the same l.s.b. in their address.

In order to determine the position of the address in a protocol message the radio has to know where the message starts and ends, this can be done in one of two ways: If the RTS/CTS HANDSHAKE option is turned on (option only available in RS232 Full Handshaking and 5V TTL radio versions), RTS should be activated before commencing a message, CTS will be activated in response and the message may be loaded. The first character received after CTS becomes active is considered to be the start of the message. Transmission will start as soon as enough characters have been loaded for the protocol address to be extracted and the route determined from the routing table. Transmission continues until RTS is de-activated, CTS will drop when transmission is complete. CTS may also drop if the serial input buffer becomes more than ¾ full to implement flow control, if this happens RTS should be kept active until CTS is re-activated, more characters may then be loaded or RTS may be dropped.

If the RTS/CTS HANDSHAKE option is turned off or is not an available option, the radio relies on gaps in the serial data to determine the start and end of messages. A gap equivalent to two character periods at the serial port baud rate is treated as a message end. The first character received after such a gap is treated as the first character of the next message.

When RFT ROUTING mode is enabled the “NETWORK ID” and “RADIO ADDRESS” fields

must be filled out such that every radio in a system has the same network id, but a different radio address. Notes should be kept detailing the installation of radios and their addresses.

The master station radio must be programmed with a routing table; this is accessed in the “EDIT

MODEM/INTERFACE” menu by setting “ROUTING TABLE” to “ON” and selecting “EDIT ROUTING TABLE”. This selection leads to several pages of protocol addresses, the route by

which every protocol address is reached must then be entered, for example if the device with protocol address 37 is physically connected to the radio with radio address 23, and radio 23 is

accessed from the base station via relay radios 4 and 19, then the field entitled “ADDR 37”

should be loaded with the route “4,19,23”. If the devices with protocol addresses 65 and 93 are

physically connected to radio 45 and no relays are required then the fields entitled “ADDR 65”

and “ADDR 93” should both be loaded with “45”.

6.3.2 Power-Save Operation With RFT Routing

When RFT ROUTING mode is enabled in the configuration programme two further fields appear

entitled “MIN PWR SAVE ADDRESS” and “MAX PWR SAVE ADDRESS”, if power save

operation is not required set both these fields to zero. If power save operation is required it is enabled by setting the “RADIO ADDRESS” to a value

greater or equal to “MIN PWR SAVE ADDRESS” and less than or equal to “MAX PWR SAVE ADDRESS”. The radio will then enter low power standby mode for the time programmed in the “PSAVE ON TIME” field in the main edit menu, it will then wake up and check for an incoming

signal, if none is present it will return to sleep and repeat the cycle. If a signal is detected the radio will stay awake until a reply to the outward-bound message has been returned.

Note that if “DTR SHUTDOWN” is enabled a radio remains completely shut down while DTR is inactive, it will not wake up according to the power save timer to see if any incoming messages are present. This mode should therefore only be used in conjunction with real time message scheduling.

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6.3.3 Serial Port Handshaking With RFT Routing

When RFT ROUTING mode is enabled the RS232 port lines DTR and DSR, can be used to

assist in power saving. The RTS and CTS lines are optionally used according to the “RTS/CTS

HANDSHAKE” option in the “EDIT MODEM/INTERFACE” menu for flow control. When the

slave is ready to accept data it should assert DTR, DSR will be asserted in response and the

received message will be output to the device. The “HOST INACTIVITY TIME” field in the set up

programme defines a time limit for the device to assert DTR. If this time limit is exceeded the radio sends back a reply indicating the destination device failed to respond and the link is cancelled (this message is not output to the device connected to the master station serial port). After sending a response, the slave may then release DTR and return to power save mode. Note that as long as DTR is asserted the radio will not return to its power save mode (if enabled in the setup programme). DSR will remain asserted in this case.

If use of the handshake lines is not required DTR should be connected either to a voltage of +3.5 to +15V such that sleep mode is never allowed.

6.3.4 Timeouts in RFT Routing Mode

When a transmission from a master station radio is made in RFT ROUTING mode the radio will calculate a timeout for a reply, this calculation is based on many configuration parameters including the radio baud rate, lead in delay, host inactivity time, maximum message length, power save timing etc. If power saving is enabled and the baud rate is low this time can be large (the calculation limits the result to a maximum of 4.25 minutes. To reduce the possibility of “hung” radios the destination radio will send a link-closing message if the destination slave does not reply. This link-closing message is only used by the radios to close the link, it is not passed to the device connected to the master station radio.

If the device connected to the master station radio itself times out before the radio link does, it can send another poll, radios along the link will cancel the previous route and set up the new one. The exception to this is the previous destination radio if it is still trying to wake up its slave, it will ignore the new message and try to download its original message when the slave awakes, a conflict will then arise if a reply is sent. To avoid this situation the master timeout time should

allow the maximum “HOST INACTIVITY TIME” to expire plus the time required to get a

message and its reply through the link.

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7 INSTALLATION

7.1 INTRODUCTION

Correct installation of the WSN radios should ensure reliable data communications for many years. The most important installation points to remember are:-

Suitable antenna system mounted at the correct height & polarisation to achieve the required

distance.

Reliable power supply capable of supplying the correct voltage and current. Correct installation for the environment. Correct interface and set-up.

Assuming the unit has been correctly installed and tested at the correct data speed, other factors that may affect the performance include the RF power (normally specified by the regulating authority), the local topography and the weather.

7.2 POWER SUPPLIES

The WSN can be powered from any power source provided that the voltage is between 9.6VDC & 16VDC with a –ve GND. If a +ve GND system is in use, an isolated converter will be required.

The WSN requires a supply capable of providing between 300mA and 2.5A depending on the maximum transmit power required.

Under no circumstances should the output of the supply rise above 16VDC. For 240/110VAC, 50VDC or 24VDC, a range of uninterruptible power supply units are available

with a in-built charger and power fail indication. A range of suitable Gel type batteries is available should a back-up supply be required during power failures.

7.3 EFFECTIVE RADIATED POWER (ERP)

The Radio Frequency (RF) Power allowed can be specified in two ways:

The “Terminated power into 50 ohms”, which in the case of the WSN would be a

maximum of 5W.

The “ERP”, which is the actual radiated power, taking into account the gain/loss of

the antenna and loss in the feeder. Hence, if we use an aerial with a gain of 3dB (x2) and assume no loss in the cable, the ERP with an input of 5W would be 10W.

The gain of an antenna is very useful as it enables lower power transmitters to be used in many cases in place of high power transmitters, with the advantage of a much lower current consumption. For example if the ERP allowed for a link is 5W, then a WSN operating at 5W into a unity gain antenna, would require a supply current of 2.1Amps to provide an ERP of 5W. If however, we use an 8 element directional Yagi with a Gain of 10dB, we would only need 500mW of RF Power for the same performance. With a WSN operating at 500mW, the current consumption would only be 600mA. If the site is battery or solar powered then the saving is very significant. Care must be taken when setting the power within a MPT1329/1411 system, as permitted RF power is specified as a maximum ERP.

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7.4 ANTENNAS, COAX FEEDERS & PERIPHERALS

Antenna Types

Typical

Gain

Polarisation

Use

Vertical Whip

0dB

Vertical

In-house testing and local use Helical

- 3dB

Vertical

End Fed Dipole

0dB

Vertical

Local Scanner or Multi-point system Folded Dipole

0dB

Vertical/Horizontal

6dB Co-linear

+6dB

Vertical

Wide area Scanner 3dB Co-linear

+3dB

Vertical

12 Element Yagi

+12dB

Vertical/Horizontal

Outstation or point to point link 4 Element Yagi

+8dB

Vertical/Horizontal

Corner Reflector

+10dB

Vertical/Horizontal

Outstations in areas of bad Interference or where radiation must be kept to a minimum

Patch Antenna

0dB

Vertical/Horizontal

Kiosk or Wall mounting

7.4.1 Antennas

Apart from the radio modem, the antenna is probably the most important part of the system. The

wrong choice or a bad installation will almost certainly impede the product’s performance.

Depending on the application either an omni-directional or directional antenna will be required.

7.4.2 Types of Antennas

We can offer a complete range of antennas to suit all applications; details of some of the more popular ones are outlined below:-

7.4.3 Directional Antennas

For point-to-point communications, a directional Yagi or corner reflector is probably the best type of antenna to use, as directional antennas provide relatively high gain in the forward direction within a limited beamwidth and very good rejection of unwanted signals at the rear. The number of elements and hence the size, will depend on the gain and beam width required. Yagi antennas can be used in the vertically polarised or horizontally polarised, but communicating products should be fitted with antennas of the same polarisation. If not a loss of signal strength will occur. Use of both vertical and horizontal propagation can be very useful on single or repeater sites where isolation is required between communication paths. Using differently polarised antennas for each path will increase the isolation, which will reduce possible interference between the paths.

7.4.4 Omni-Directional Antennas

With approximately 360-degree radiation pattern, this type of antenna is ideal for the central site of a scanning station or where communication to a group of widely dispersed outstations is required.

7.4.5 Patch or Plate Antennas

The patch or plate antennas are normally rectangular or round, with a back plate of aluminium or stainless steel. A polycarbonate or ABS cover is fitted to protect the antenna from the environment. This type of antenna can be produced in different sizes with various radiation patterns to suit the application. Depending on the construction and radiation pattern, the gain is usually between -3dB to + 3dB. Their use is very popular on roadside kiosks, buses, trains, aircraft, or where covert communication is required.

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7.4.6 Antenna Mounting

Cable Type

Attenuation per 100ft

Attenuation per 100m

RG58

13.0dB

37.0dB

RG213

6.0dB

17.5dB

LDF2-50 3/8inch Foam Heliax

2.44dB

8.0dB

LDF4-50 1/2inch Foam Heliax

1.60dB

5.26dB

LDF5-50 7/8inch Foam Heliax

0.883dB

2.9dB

LDF6-50 1-1/4inch Foam Heliax

0.654dB

2.15dB

LDF7-50 1-5/8inch Foam Heliax

0.547dB

1.79dB

Location: The antenna should be mounted in a clear area, as far away as possible from

obstructions such as metal constructions, buildings and foliage.

Height: The WSN operates in the UHF band, which requires near line of sight

communication. Hence, for extended ranges the height of the antenna is important.

7.4.7 Polarisation

A Yagi or corner reflector antenna can be mounted for vertical or horizontal polarisation. Scanning systems employing a vertically polarised antenna will necessitate the outstation antennas to be of the same orientation. In vertical polarisation the elements are perpendicular to the ground. By mixing polarisation within systems, unwanted signals can be reduced by as much as 18dB. However, such systems require detailed planning.

7.4.8 Alignment

If a directional antenna is to be used, it will need alignment with the scanner or communicating station. A map and compass can be used, but the final adjustment should be performed by measuring the receive signal strength (RSSI) from the scanner, as outlined in the operations section.

7.4.9 Antenna Coax Feeder:

As with the antenna, the use of the wrong coax feeder can seriously affect the performance of the system. Hence, the coax cable should be selected to give a low loss over the distance required. For outstations in the local vicinity of the scanner/ base station, the loss is not very important but for distant stations the loss is very important. As a rule of thumb, never operate a system with a loss of more than 3dB.

To illustrate the point, a 3dB loss in the feeder will result in a 50% loss in transmitted RF power and a 50% reduction in the received signal strength. Therefore, double the received signal strength will be required for the same bit error rate. Although increasing the RF power will compensate for the loss in transmitted power, there is no effective way to improve the received signal strength.

Coax cable should be installed in accordance with the manufacturers’ instructions, with cable

runs kept as short as possible. Sharp bends, kinks and cable strain must be avoided at all costs. If long term reliability is required, the cable must be securely mounted to avoid excessive movement and longitudinal strain, due to high winds, rain and snow.

7.4.10 Signal Loss v. Cable Length at 500MHz

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7.4.11 Coax & Connectors:

ANTENNA

BUSY

SYS

Prog/Channel

Switch

TXD

RXD

INPUT

-12V+

50 Ohm coax connectors of a good quality should be used, termination must be in accordance with the manufacturer's specification, any special tools required to terminate the connectors must be used. Connectors exposed to the environment should be sealed to prevent the ingress of moisture. If the cable is penetrated by water a high loss will occur and the cable will need to be replaced. Once assembled it is advisable to test the cable and connectors for open and short circuits.

7.4.12 VSWR Measurement:

Voltage standing wave ratio (VSWR) is the ratio of detected volts from the forward RF power, to the detected volts from the reflected (returned) RF power. This ratio is used to measure the combined coax cable and antenna match. A good match will ensure that most of the RF Power is radiated, whereas a bad match will result in the reflection of a large amount of the power, thereby reducing the transmitter's range. A perfect match will give a 1:1 ratio and bad match will give 2:1 or higher. For guidance, a good system will measure between 1.2:1 and 1.5:1.

7.4.13 Lightning Arresters

At high or exposed sites, the use of a lightning arrester is recommended. This in-line device fits between the antenna and the product with an earth strap connected to ground. Should a lightning strike occur, most of the energy should be diverted to ground leaving the equipment with little or no damage.

7.5 MOUNTING & INSTALLATION

The WSN is built into tough durable aluminium enclosure that can be mounted in any plane, but should not be exposed to rain etc. as the enclosure and connectors do not meet the relevant IP ratings. If IP65, 67 or 68 is required then an additional enclosure will be required. A number of suitable enclosures are available as options.

7.6 FIXING DETAILS

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Page 34

FF-Automation Oy

Eräkuja 2, 01600 Vantaa, FINLAND,

http://www.ff-automation.com,

email: [email protected]

Tel: +358 10 2190 500

WSN Manual Page 34 of 34 Rev. G – 4 March 2007