GSM modem troubleshooting

Remote diagnostics

Modem connection

With a modem connected to a master module, it is possible to do troubleshooting and update an application remotely. You can connect either with IQANdesign or IQANrun, and have access to every function such as measure or update application, just as if the PC was connected locally over CAN or USB.

Choosing a modem in the machine

On all master modules that have an RS 232 port, e.g the IQAN-MD3, you can connect a GSM modem.
The master connects to a modem over RS 232 using standard AT commands, therefore it is possible to use GSM modems from different vendors. Unfortunately, different modems have slightly different implementation, with variations in e.g. start-up procedures. Also specific models are usually only available for a short period, and the replacement model may not be fully compatible.
To avoid these problems, the recommended modem to use is the IQAN-G1. Using the IQAN-G1 eliminates potential problems with IQAN master to modem communication, such as start-up times and configuration of the modem.

Subscription requirements

For GSM modems, a GSM subscription with GSM data capabilities is needed. This is named mobile terminated, or Circuit Switched Data.
Sometimes these services are sold with the product name telematics card, the SIM card may also be referred to as a M2M card (machine to machine). Please contact your local provider.
Some SIM cards have two or three numbers. In those cases, it is the data number that should be used.
Also note that in some parts of the world, GSM data is not available as a service.

Connect via modem

Please see the user manual for IQANrun / IQANdesign on how to connect via modem.

Troubleshooting guidelines

Troubleshooting RS232 connection

If the IQAN-G1 is not found by the master module, the RS 232 connection is a probable cause.
It is easier to diagnose the problem if the application contains the SIC ‘Modem status’.
If the modem status is unavailable:
  • Check RS 232 connection. See installation information in instruction book IQAN-G1
  • Also check the ground connection between the IQAN-G1 and the IQAN master module.

Troubleshooting when connecting from a landline to GSM-modem

A common mistake is that the call gets connected as voice instead of data. If the call gets connected, but communication fails, this is a probable cause.
This can be avoided by making sure that the number called is a number that only allows data calls (see subscription requirements above).
However, for machines located in some areas, this still may not work. In that case, it is worth using GSM also on the calling side.

Troubleshooting when connecting from GSM to GSM

GSM to GSM is usually the most reliable method when it has been set up, but it normally does require some initialization. Just use a cell phone connected to the PC to make the call to the machine. This is not possible on most modern smartphones. If it is possible, use USB to connect the cell phone to the PC instead connecting over Bluetooth.
A problem that can appear in some areas is that the local GSM station does not set up the correct communication by default. This can be a problem both for the IQAN-G1, and for the cell phone used as a modem by the PC.
To force the correct method:
  1. Go in to Control panel/Phone and Modem options on the PC.
  2. Select the PC modem.
  3. On the advanced properties, add the string "AT+CBST=71,0,1" (depending on phone, you may leave out the "AT", only using "+CBST=71,0,1"
if the cell phone does not connect, also add the following string:
  1. On the advanced properties, add the string "+CHSN=1,1,0,4”
The strings must be separated with a “;”. Example:

This will set up a data session as non-transparent from the beginning. A positive side effect is that it will also force a data call. Depending on your phone or area, the string "+CBST=71,0,1" may cause it to not work at all. In that case, it could either be left out, or be replaced by "+CBST=7,0,1".

G1 to G1 communication setup

It is possible to use the IQAN-G1 modem as a dialup modem so you can connect to a system with another G1 modem as the receiver. You will need to make a special RS232 connector to make the computer think it is talking to a standard modem. Connect the -BAT from the G1 modem to pin 5 and the DATA-IN to pin 3 and the DATA-OUT to pin 2. On the RS232 connector you will also need to connect the 1 and 4 pin together and the 8 and 7 pin together.
Now all you need to do is add a standard 9600 bps modem in windows and it should be ready for use in IQANrun. No extra AT commands were needed when this was tested.
With this setup you will get a 10 sec delay when disconnecting, this is due to IQANrun trying to do a hardware hang-up. After the 10 sec IQANrun will do a software hang-up instead. If you have IQAN 3.0 you will need to cut the power to the G1 modem to make it hang up.

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