APPENDIX 3 INSTALLING AND USING THE RS 485/422 SERIAL PORT MODULE. Vaisala DMP248

A PPENDIX 3 ________________________________________________________________________

APPENDIX 3

INSTALLING AND USING THE RS 485/422 SERIAL PORT MODULE

APPENDIX 3 ..................................................................................................................................................... 105

I NSTALLATION ................................................................................................................................................. 106

O PERATION ...................................................................................................................................................... 106

N ETWORK CONFIGURATION ............................................................................................................................. 108

Single loop operation ................................................................................................................................. 108

Dual loop operation.................................................................................................................................... 110

C HECKING THE SERIAL PORT NETWORK OPERATION ........................................................................................ 112

STOP mode................................................................................................................................................ 112

POLL mode................................................................................................................................................ 113

RS 485 network settings............................................................................................................................. 114

S PECIFICATIONS ............................................................................................................................................... 114

V AISALA ________________________________________________________________________ 105

A PPENDIX 3_________________________________________________________________________

Installation

Switch the transmitter off.

Resistors R2, R3 and R4 between connectors X4 and X5 in the component board in the cover of the transmitter are removed with side-cutting pliers. The module is plugged in connectors X4 and X5 on the main board of the DMP248 transmitter; connector X1 on the module board to connector X4 and connector X2 to connector X5.

RX GND TX

Jumper ( ) selections for the

RS 485/422 serial bus module

Single pair

X1 X2

X2

RS 485/422 serial bus module

X5

TX

X1

R2

R3

RX

R4 X4

+ +

Ch1 Ch2

-

X6

T X HI

TX LO

RX H I

RX LO

24V

+ -

Dual pair

X1 X2

Cut off the resistors R2, R3 and R4 on the main board.

New signal names for X6 screw terminal are on the module.

Follow the instructions on the module:

X1 to X4 and

X2 to X5 on the mother board

NOTE! If the transmitter is NOT at the end of the bus OR the line has a dynamic line termination, the resistors R3 and R6 have to be removed!

R6

R3

Connect the data wires to screw terminal X6 on the main board.

Switch the power on.

Operation

The DMP248 transmitters can either be given an address or operated without an address. Both single and dual loop wiring with half duplex

106____________________________________________________________________M210492 EN A

A PPENDIX 3 ________________________________________________________________________ connection can be used. No address is needed when only one DMP248 transmitter is used; when several transmitters are connected to the same line, each transmitter must be given an address in the initial configuration.

A single transmitter can get its operating voltage from the master or it can have its own (floating) power supply or it has the power supply module in use.

The serial line structure is a parallel interfaced chain (daisy chain). At the ends of the serial line there must be a DMP248 transmitter, dynamic line adapter (120 ohm resistor in series with a 33 nF capacitor) or line master. If a branch line is made with a junction box, the branch should be shorter than 3 meters.

When connecting the device, follow the instructions given in the figure in Chapter 1.

SINGLE LOOP WIRING

TWISTED PAIR WIRING

HOST COMPUTER

TX HI

TX LO

RX HI

RX LO

RX HI

RX LO

TX HI

TX LO

DMP248 transmitters

1 to n pieces

-

RX HI

RX LO

TX HI

TX LO

NOTE: DYNAMIC LINE TERMINATION

REQUIRED IF NO DEVICE

AT THE END OF THE BUS.

120R

33 nF

DUAL LOOP WIRING

TWISTED PAIR WIRING

HOST COMPUTER

TX HI

TX LO

RX HI

RX LO

RX HI

RX LO

TX HI

TX LO

DMP248 transmitters

1 to n pieces

RX HI

RX LO

TX HI

TX LO

NOTE: DYNAMIC LINE TERMINATION

REQUIRED IF NO DEVICE

AT THE END OF THE BUS.

120R

120R

33 nF

33 nF

V AISALA ________________________________________________________________________ 107

A PPENDIX 3_________________________________________________________________________

The RS 485/422 module has separate lines for transmitting and receiving, but they can be connected together with jumpers. Dual loop connection is the factory setting; when a single loop connection is used, the positions of jumpers in connector X4 on the module must be changed.

The HI of the receiving line is approx. 0.6 V and its LO is approx. 0 V in order to reduce noise on the lines when no data is transferred

(idling). Both lines are terminated with a 120 ohm resistor in series with a 33 nF capacitor. When operating the transmitter through a single pair, naturally only one line terminal impedance is in use. The line must not be terminated with a resistor alone, as then the power consumption increases too much.

The data lines can withstand short circuit to ground and to each other.

They do not survive connection of supply voltage to the data lines.

The module must be mounted on the main board in the right direction.

It can be mounted in the wrong direction or to the wrong pins without breaking the module; it simply does not work then.

Network configuration

Single loop operation

Bi-directional data on one pair is one of the great advantages of the

RS 485 line. Set jumpers in connector X4 on the module board as shown in the figure below.

X1 X2

X4

X4

This jumper setting connects RX HI to TX HI and RX LO to TX LO and selects only one common line termination. The HI and LO terminals of the RX pair can now be used for operation.

Supplying power from the same end to the whole network prevents common mode voltages from rising too high (over 7 V).

108____________________________________________________________________M210492 EN A

A PPENDIX 3 ________________________________________________________________________

•

•

Connect wires to the transmitter's serial connector.

Check the wiring.

The following procedure must be repeated with all transmitters.

• Open the transmitter cover.

• mounted.

Pull out the RS 485/422 serial port module, if it is already

• Set the serial port of the terminal to 4800 baud, even parity, seven data bits and one stop bit, full duplex (4800 E 7 1 FDX).

RX GND TX

X17

NOTE

• The serial settings of the transmitter must also be 4800 E 7

1 FDX and the transmitter must be in STOP mode. If these factory settings have been changed, they must be changed back. Connect the

RS 232C port of the terminal to connector X17 on the top of the main board and switch the power on.

• Set the address of the transmitter; it can be any number between 1 and 99. In this example the address is 22:

>addr 22

Address : 22

• Set the serial bus settings according to your network specifications. This setting will become valid after next RESET or power off:

•

>seri 2400 e 7 1 h

2400 E 7 1 HDX

Set the transmitter in POLL mode:

>smode poll

Serial mode : POLL

The SMODE command must be given last.

V AISALA ________________________________________________________________________ 109

A PPENDIX 3_________________________________________________________________________

NOTE The transmitter outputs no prompt (>) after the SMODE POLL command and it only reacts to commands which include its address.

•

•

• places.

Check that the transmitter responds to its address:

>send 22

Td= -47.4 'C T= 29.1 'C

Disconnect the terminal.

Check that the jumpers in connector X4 are in the right

X1 X2

X4

X4

•

•

Remount the RS 485/422 serial module.

Close the cover.

• When all transmitters on the network have been configured, switch them off.

Dual loop operation

The following procedure must be repeated with all transmitters.

• Open the transmitter cover.

• mounted.

Pull out the RS 485/422 serial port module, if it is already

• Set the serial port of the terminal to 4800 baud, even parity, seven data bits and one stop bit, full duplex (4800 E 7 1 FDX).

• The serial settings of the transmitter must also be 4800 E 7

1 FDX and the transmitter must be in STOP mode. If these factory settings have been changed, they must be changed back. Connect the

110____________________________________________________________________M210492 EN A

A PPENDIX 3 ________________________________________________________________________

RS 232C port of the terminal to connector X17 on the top of the main board and switch the power on.

When dual loop is used, the jumpers in connector X4 on the module board must be as shown below.

X1 X2

X4

X4

• Set the address of the transmitter, it can be any number between 1 and 99. In this example the address is 22:

>addr 22

Address : 22

• Set the serial bus settings according to your system. This setting will become valid after next RESET or power off:

>seri 2400 e 7 1 f

2400 E 7 1 FDX

• Switch echo on:

>echo on

ECHO : ON

>

• Change the serial output mode into POLL:

>smode poll

Serial mode : POLL

The SMODE command must be given last.

NOTE

NOTE The transmitter outputs no prompt (>) after the SMODE POLL command and it only reacts to commands which include its address.

• Check that the transmitter responds to its address:

V AISALA ________________________________________________________________________ 111

A PPENDIX 3_________________________________________________________________________

>send 22

RH= 24.4 %RH T= 29.1 'C

•

•

Disconnect the terminal.

Check that the jumpers in connector X4 are in the right places.

X1 X2

X4

X4

•

•

•

•

Remount the RS 485/422 serial module.

Close the cover.

Repeat this setting procedure with each transmitter.

When all transmitters on the network have been configured, switch them off.

Checking the serial port network operation

Normally measurement readings are asked when the transmitter is in

POLL mode; then the command must include the address of the transmitter. If the settings of the transmitter need to be changed, the transmitter is switched to STOP mode with command OPEN; commands can then be given without address. When the line to the transmitter is closed, it returns to POLL mode.

STOP mode

Open the line to the transmitter: open 22<cr>

DMP 22 line opened for operator commands

Transmitter no. 22 is now temporarily set to STOP mode; it accepts commands sent without address until CLOSE command is given.

Individual settings can now be easily modified. Do not open more than one line at a time.

112____________________________________________________________________M210492 EN A

A PPENDIX 3 ________________________________________________________________________

Use command ? to find out the settings of the active transmitter:

? <cr>

DMP248 / 1.01

CPU serial nr : 0

Keyboard type : 0

Address : 7

Output units : metric

Baud P D S

Serial mode

: 4800 E 7 1 FDX

: STOP

Output intrv. : 0 min

Mtim : 32

Pressure : 1013.25

Analog outputs

Ch1 0.00 ... 10.00 V

Ch2 0.00 ... 10.00 V

Ch1 ( RH )

Ch1 ( RH ) lo hi

0.000 %RH

100.000 %RH

Ch2 ( T )

Ch2 ( T ) lo -20.000 'C hi 180.000 'C

Transducer :

PRB serial nr : 0

Calibr. date : 0

When the necessary settings have been given, close the line to transmitters (the command closes all open lines):

>close line closed

CLOSE command is always given without address. If no lines are open, there will be no response to the CLOSE command.

POLL mode

If a transmitter has been set to POLL mode, it will respond only to commands which include its address: send 22

Td= -47.4 'C T= 29.1 'C

Addresses from 1 to 99 can be used. According to the RS 485/422 standard a maximum of 32 devices can be connected on same bus, but the number can be increased if the line length and/or baud rate is reduced.

The line terminations must be dynamic; e.g. an RC circuit is used instead of a simple resistor termination. Each RS 485 module has a dynamic line termination so it can be used at the end of a line.

V AISALA ________________________________________________________________________ 113

A PPENDIX 3_________________________________________________________________________

RS 485 network settings

DMP248 settings

Full duplex/half duplex

Echo on/off

Terminal settings

Line feed after carriage return

HDX/FDX single pair dual pair

HDX

OFF

FDX

ON single pair dual pair yes

FDX no

FDX

When terminal is set to general <lf> (line feed) after <cr> (carriage return), the listings will have two line feeds when also the DMP248 transmitters send line feed.

Specifications

Connections on the main board

Assembly

Board dimensions

Operating mode

Berg sockets screw terminals 0.5 mm² wires, stranded wires recommended plug-in module

40 x 28 mm

(single or dual pair wiring)

Network: network type cable type line length max.

number of devices data speed half duplex daisy chain twisted pair

1000 m (3000 ft)

32 devices on line

9600 baud max. for DMP248 transmitters operating mode polling mode common mode voltage range ±7 V

Operating temperature

Storage temperature

-40...+60 °C

-40...+70 °C

114____________________________________________________________________M210492 EN A