Archive for the “Comunic. GSM/GPRS” Category

Today we are going to touch on and dig out some old, published articles here on from several months ago, nearly two years ago. Do you remember this article from the end of 2009?

In this article, I talked about the imminent appearance of the new EU3 Cinterion module highlighting that one of its greatest strengths was that it supported the new 900MHz UMTS band that was approaching. The following is worth remembering from this article:

“From a technical point of view it’s better because it offers a greater coverage and penetration than the current UMTS2100, which is ideal for rural coverage and even coverage in cities where the greater the ability to penetrate, the better the coverage in buildings.

It’s obvious from an economic point of view.  One reason is that in order to have a greater scope to cover a specific area, you need to install less base stations with UMTS900 than UMTS2100. Another reason is that the current GSM stations are still valid and they only require small, inexpensive adaptations unlike the UMT2100.

I only have one more tip for those of you who are going to start a new project today with GSM/GPRS modules and who are looking into the future and who are evaluating modules from different manufacturers. The tip is that you read the announcement in the news about the new EU3 module published on Cinterion’s website. Pay special attention to this title, “Cinterion Announces First UMTS Module to Support Seamless 3G Transition for Existing GPRS/EDGE Designs”.


A little later in the article from May 2010:

We talked about everything more deeply on a technical level with the 3G 900MHz (it is recommended reading). One thing to note from this article, as many people asked and will ask this question, is that both in the text as well as in reader’s comments is the clarification that current GSM/GPRS technology (at 900MHz) will coexist with the new 900MHz UMTS.

Finally 10 months ago I posted an article on the EU3 module’s TCP/IP stack:

Note the last paragraph where it says:

“Finally here is a detail worth noting. The same B2B connector and (nearly) the same pinout as in the TC63i have been used with the EU3 Cinterion module. Therefore, whoever is designing a board to use with the TC63i, I recommend you to take a look at an application note called EU3_e-migration (which is part of the EU3 documentation) as it shows small differences to consider when moving from the TC63i to the EU3. Or rather, this document allows us to design a board in a way that we can use the TC63i or EU3 interchangeably, with obvious advantages that we can use in the future. If some of you are undecided whether to use a MC55i or a TC63i with a new design (I see this happen often), you should consider the compatibility with the EU3. At least it helped me to decide.”

Those who betted on the new EU3 Cinterion module or made a design with a TC63i and considered the application notes to make a compatible circuit like we talked about here, they can start to reap the benefits from the 9th of September (because it’s an implementation process that will last a couple of years). :)

Here you have more information of the implementation of the new 900MHz UMTS:

Well, I hope that this article has been interesting for some of you and satisfying for others who have made the right choice. I will now continue working on the new version of the MTXTunnel v6.0 manual which will be out soon. :)



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If you make applications with GPRS modems, a lot of the time you will encounter the problem that IP addresses, which are assigned by the network operator, are dynamic.

What’s a dynamic IP? It means that every time one of your modems connects to the GPRS network, the operator will give it a different IP address.

For a lot of applications it won’t matter. For example if I have a modem that collects data from a datalogger and the modem sends the data to a central server via GPRS at the end of the day, it doesn’t matter if the modem’s IP address is dynamic. So in this case it’s the modem that makes the connection to the central server (which must have a fixed IP address or a DNS at least).



The problem arrives when we want to work with GPRS modems in server mode i.e. with modems that are permanently connected to GPRS and are listening to a specific TCP port waiting for incoming connections (typical remote maintenance). In this situation you need to know the modem’s IP address. There are various solutions to resolve this problem. I will talk about one of them today – DynDns service.

With DynDns you can assign a specific IP address to a DNS for free. To do this, you just have to open an account

Let’s look at a concrete example.

I’m not going to give you an example with Java instead we are going to look at it with AT commands. Doing it with Java (from the following) is practically that same as using the ATCommand class.

Imagine that we have created our own account in with the following data:

DNS server:
Login: mylogin
Password: myPassword
Current IP: 80,100,101,102 (the IP assigned by the operator)

What I want to achieve with the modem is that the address points to the IP address (which was assigned by my operator at a given time). This means that if do a ping from my PC to it will have the same response if I do a ping to

Which AT commands are required to make point to the IP 

Well to configure the GPRS connection profile (with Movistar) use the following:


To configure the http service profile use the following (note that for DynDns you need to use basic authentication protocol with login and password, therefore we turn on hcAuth):


Finally we keep the socket open to initiate the HTTP connection:

^SIS: 0, 0, 2201, “HTTP/1.1 401 Unauthorized”
^SIS: 0, 0, 2200, “HTTP Redirect
^SIS: 0, 0, 2201, “HTTP/1.1 200 OK”
^SISR: 0, 1
Este último evento ^SISR: 0,1 indica que han llegado datos al socket “0″ y tenemos que leerlos con AT^SISR:
^SISR: 0, 17


By only doing this, we have associated the DNS to the IP for free and without having to pay a monthly fee to the operator. If I remember correctly they charge around 12 Euros + VAT for each fixed IP address. This is something that we will later incorporate into MTXTunnel, although possibly we may only do it in the advanced version.

Well, I hope that this post has been interesting for you and useful for your Siemens / Cinterion GPRS modem applications, as you can see you can do everything with them they are marvellous. ;)

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Today I am going to talk about a little Multiplex feature in Siemens modems. As you know, some of the current modems like the MTX65+G  (GPRS+GPS modem) and the imminent MTX-HC25+PLUS (UMTS+GPS) have a single communication serial port.

There may be some applications where we’d like to have more than one serial port.

Why would I want more than one serial port?

Well for example it could be to maintain a GPRS communication through a serial port, to monitor the coverage level through another serial port and to obtain GPS coordinates through the other serial port. So yes it is possible but we use Multiplex mode for this.

The Multiplex protocol (GSM 07.10 y 3G TS 27.010) enables an asynchronous serial interface to be split into three virtual channels. It’s basically a communications protocol that encapsulates communications between the host (e.g. PC/ microprocessor) and a corresponding device (modem) with three virtual serial ports.

How do you use it?

Siemens provides some drivers for Windows (XP/2000) to be able to use this feature. If you don’t want to use a PC with Windows and you want to use a microprocessor for example, you can install the Multiplex protocol. It’s quite complex but it can be done.

To use driver in Windows, all you have to do is install the Siemens WinMux application. When you run it a window like this will appear:

Driver Multiplex All you have to do is have the modem physically connected to the PC’s COM port so that the driver will find it by clicking on the “Start Scan” button. Once the modem is connected it will suggest some port numbers as to where you should install the 3 virtual serial ports. As you can see in the figure above, I have installed it in COM24, COM25 and COM26.

After installing the driver, go to Start-> Control Panel-> System-> Hardware-> Device Manager:

Driver Multiplex  You will se that the “Serial Multiplex Driver” has been assigned to a COM, in my case COM1. If you right click on the installed driver’s properties you will be able to change the assigned COM, the speed and the virtual COM numbers.

One last thing, there’s a catch with the number assigned to each of the COM ports (it’s probably Windows’ fault) and the catch is that it doesn’t let you install it on any COM number. For example there are programs which don’t accept high COM numbers (COM24/COM25/COM26). If you want to change it, I have already registered to Windows you already know:

Start -> Run -> Manage

I searched for a VirtPort1 string and I changed the assigned COM for another one that interested me. It worked without any problems although I had to restart the computer after making a change before using it.


If we no try to open up to 3 HyperTerminal windows, each one associated with a virtual COM port, and we send AT commands you will see that it works without any problems.

I hope you found this interesting, see you next time. ;)  

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