Archive for October, 2008

I have wanted to write a post about this for quite a while in case somebody would find it useful. It’s about providing Bluetooth connectivity to our Siemens TC65 or MTX65 modems. To do this, by way of example I will describe how to make a Bluetooth-GPRS gateway. At first glance, this type of gateway may not seem useful but as I say by way of example I will give you some ideas. Maybe it makes sense in other applications. For example let’s imagine a project where we want to have Bluetooth connectivity with a machine controlled by an MTX65 that has an embedded Java program. For example with Bluetooth a person who has a PDA can maintain it without having to connect any cables or open any machine.

I’m going to go through it very quickly, let me know if you have any questions as I’m just going to describe how to make the application without going into too many details.

To do this I am going to use an MTX65 modem with the MTXTunnel application embedded inside and a Bluegiga WT11 Bluetooth module that I will use with its development board (the MTX65, the MTXTunnel firmware and the WT11 are all distributed by Matrix in Spain). The reason for using the WT11’s development board is because it has an RS232 port and it’s very easy to connect it to an MTX65 simply with a serial cable. Remember that the WT11 Bluetooth module is in class 1 and therefore theoretically we will have a range of about 100m. If we want a smaller range we can choose the WT12 which is a class 2 Bluetooth module that theoretically has a range of about 20m.

gateway bluetooth gprs

On the other hand I will use my amazing Fujitsu-Siemens T830 mobile with Windows Mobile :) I installed the mobile version of this onto my mobile from the well known puTTY terminal (a small program similar to a HyperTerminal).

The SPP (Serial Port Profile) must be enabled in the Bluetooth module’s configuration. All you have to do to check this is find out the SET command response which is sent to the WT11 from a PC with a HyperTerminal connected. This command shows the current settings.

If you have already enabled the SPP in the WT11 Bluetooth module and you have already configured the MTXTunnel configuration parameters (the client mode, the IP and the port the server will connect to), we can connect the WT11 Bluetooth module to MTXTunnel (through the RS232 connector in the development kit) and supply power to both. By doing this MTXTunnel will automatically connect to the IP address and the specified ports via GPRS. The WT11 will keep waiting to receive an incoming Bluetooth connection.

Now touch the phone. First, install puTTY. Once this is installed we have to pair the phone up with the WT11 via Bluetooth. With the telephone’s Bluetooth connection manager, you can find out the WT11’s Bluetooth services in which you should see the SPP (Serial Port Profile). After this is done, we will link this serial port to one of the phone’s virtual COMs.

Terminal pocketPutty

Now launch the puTTY application and open the COM that is associated to the SPP profile that we linked up earlier. When you are opening the COM with the puTTY, what you are really doing is connecting to the WT12 via Bluetooth. Once the COM is open (i.e. the Bluetooth connection is established), everything that is sent through the terminal (puTTY) from the phone to the WT12 is via Bluetooth. The WT12 then sends it through the (development board’s) serial port to the MTX65 (remember that both are linked by a serial cable). Then the MTX65 sends it to the IP address and the previously specified port via GPRS i.e. we have a Bluetooth-GPRS gateway.

I hope that this has been interesting for some of you, as you can see incorporating Bluetooth connectivity into Bluegiga modules or Siemens/Cinterion modems is really simple. See you next time. ;)  

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