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CONFIGURING SIEMENS GSM MODEMS Application Note 19For Use With Davis Weather Stations

INTRODUCTION

This application note describes some of the considerations and configurations options necessary to connect aSiemens M1- or M20-based GSM modem with a Davis weather station.

The Davis weather stations communicate with PCs using the Davis WeatherLink data logger.

CHARACTERISTICS OF WEATHERLINK COMMUNICATION

The WeatherLink was designed to talk directly to a PC serial port.

In order for any other connection medium to be used (such as telephone modem, radio, or GSMmodem), it must provide a transparent connection to the PC.

The WeatherLink sends a short fixed "modem init. string" upon powerup.

The WeatherLink transmits to the GSM modem at a fixed baud rate (2400 baud) which is set by dipswitch prior to powerup.

The WeatherLink is command-driven.

This means that it will receive commands from the PC and send back a response code possiblyfollowed by data. It never sends commands to, nor receives replies from, the GSM modem.

The WeatherLink can only receive calls. It never originates calls.

There are no provisions for flow control between the WeatherLink and the modem.

Do not use a GSM service that is slower than the WeatherLink baud rate.

If the WeatherLink loses power, it loses all stored data.

When it is powered back up, it will re-send the "modem init.string." If the GSM modem sends anycharacters to the WeatherLink when the GSM modem is re-powered, it could leave the WeatherLinkin an undefined state.

SETTING UP YOUR GSM SERVICE

1. Ask your provider to activate your GSM Network Data Channel at 2400 baud, instead of the usual9600.

The best results are obtained when all parts of the data path are at the same baud rate (2400).

2. Request a Subscriber Identity Module (SIM) with the Personal Identification Number (PIN) disabled.

If this is not possible, then you will have to enter and disable the PIN with either a computer or anattached handset.

3. Do not get Call Waiting, the WeatherLink can only talk to one PC at a time.

If your service has this feature automatically, use the command given below to disable Call Waiting

(M20 modems only).


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CONFIGURING YOUR GSM MODEM

Note: If you have an M1 modem and the PIN is already disabled, skip this section.

1. Connect the GSM modem to a PC running a terminal emulation program such as ProComm orHyperTerminal.

2. If required, enter your PIN using the command: AT+CPIN="","".

Make sure you include the quotation marks, and substitute your actual PIN for .

3. If you have an M20 modem, enter the command settings from the table below.

First try configuring your modem without the optional commands and add them later if you experience

problems.

4. At this point, the GSM modem is configured and does not require a PIN for operation.

CONFIGURING YOUR SOFTWARE

1. Open the Davis WeatherLink software.

2. Create a new station by choosing "New Station" in the File menu.

If you do not have any stations on your computer, this will be selected automatically when thesoftware is started.

3. In the Serial Settings Dialog, indicate that you are using a modem connection and enter the GSMmodem's phone number in the Phone Number: entry box.

4. Enter "22" in the box labeled "After Connect Wait: ___ sec".This causes the software to wait 22 seconds after the connection is made before sending anycommands to the WeatherLink.

5. Make sure the serial port selected in the Serial Settings dialog is the one for a modem attached to thecomputer.

The weather station will not be attached directly to the PC.

6. Select OK.

ASSEMBLING YOUR SYSTEM

It is a good idea to test your system "at home" before installing it in the field.

1. Connect your weather station to the sensors you will install in the field.

This step is optional, but will verify that the sensors are working.

2. Apply power to the GSM modem.

3. Connect the WeatherLink to the weather station.

4. Connect the WeatherLink to your GSM modem using a WeatherLink RADIO/SRModem Adapter(Part # 7944).

5. Apply power to the station.

You will hear three beeps if all goes well on powerup.

6. The WeatherLink's modem init. string sets the auto-answer setting to 4 rings.

See the table below for the complete list of the commands contained in the modem init. string.


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TESTING YOUR SYSTEM

1. Open the Davis WeatherLink software.

2. Either open or create a new station as described above.

If you are using the GroWeather software, use the "Connection Test" button to test the connectionbetween the PC through the phone system to the GSM modem and the weather station. If you areusing the WeatherLink software, use the "Set Time" command, or the "Bulletin" command.

3. Verify that the modem attached to the PC dials correctly, the GSM modem rings and answers, andthat the station is responding correctly.

4. Use the Bulletin or Summary command to verify that the sensors are working.5. To test that long downloads operate correctly, set the archive interval on the station to 1 minute wait

for one or two hours, and download.

6. Examine the communication error log file with the "View Log" command.

Momentary communication lapses and errors during automatic downloads will appear here. Contact yourdealer if you experience serious difficulties.

INSTALLING YOUR SYSTEM

To install the GSM module in the field, determine the optimum field location for your station and assembleyour system as described both above and in the station and modem manuals.

Siemens GSM Module M20 Initialization Commands

Function M20 Command* Comments

Load factory defaults AT&F Start from a known configuration

Set fixed GSM station baud AT+IPR=2400 Set fixed local rate to 2400 baud

AT+CBST=4 Select a 2400 baud bearer service (optional)

Enable auto-answer ATS0=4 Auto answer after 4 ring (can be set between 1 and 5)

Disable flow control AT+IFC=0,0 Disable all flow control

Disable data compression AT+DS=0 Disable data compression (optional)

Set disconnect delay ATS10=30 Allow 3 seconds, default is 1.5 seconds (optional)

Disable call waiting AT+CCWA=0,0 (optional)

Turn off command echo ATE0

Do not display result codes ATQ1

Save settings AT&W Save in user profile

* Each "0" in the command column is a zero, not the letter "O".

WeatherLink Modem Initialization String

The following commands are sent by the WeatherLink on the third beep when it is powered up:

Function Command* Comments

Enable auto-answer ATS0=4 Auto answer after 4 rings

Turn off command echo ATE0 Set fixed local rate to 2400 baud

Do not display result codes ATQ1

Select user profile 0 AT&Y0

Save settings AT&W Save in user profile 0

* Each "0" in the command column is a zero, not the letter "O".

Note: The modem initialization string sends all of these commands in one line:ATS0=4 E0 Q &Y0 &W


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configuring siemens gsm modems480

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