Last week i bought a Siemens M20T. The Siemens M20 Terminal is a GSM900 Phase II voice, data, group 3 fax and SMS terminal device. This device has been on my wish list for a long time. Although i had the ability to send SMS by using Voipbuster, using a dedicated device like the Siemens M20 has always been my favorite. Last week the Siemens M20T arrived and yesterday i took some time to do some tests. After making a straight 1:1 RS232 cable and inserting the new arrived SIM, i connected the M20T to my PC and switched on the power adapter. The LED kept on blinking, where it should burn continuously. Of course, i had to enter the PIN code, so i started Hyperterminal and sent the appropriate command. So far so good.
Now it was time to test sending a SMS to my mobile phone. That wasn’t to hard, the command for sending a SMS is quite easy and human readable:
AT+CMGS="06987654321" > TESTING 123<Ctrl+z> > +CMGS: 4
It worked. One problem though; the mobile phone displayed an error message saying the message could not be displayed? 🙁 After some searching i found out that the text mode SMS i sent with the command above, is not supported by all mobile phones. However there’s another mode to send a SMS, called PDU mode. It involves a bit more work in encoding the SMS before it can be sent to the M20T, but i found enough documentation to send my first PDU-mode SMS after 2 hours. This worked well! 🙂
The command for sending a PDU mode SMS looks like this:
The text sent is no longer human readable, the phone number is hard to recognize, but who cares if it’s working, as long as the M20T and my mobile phone understand it, it’s fine by me..
This evening i’ve started to write an interface to my Home Automation software so that i can send SMS messages whenever interesting things happen in and around my house.