PDU and Text mode


Hi friends
I want to interface q2686 module to the host processor. The main purpose is for the sms! . The modem support text and PDU format.
Text - 7bit coding
PDU - 8 bit octet coding scheme … right ?

So i can send message on text and PDU format right? Suppose i am sending message in PDU format to one mobile phone wch is having only a text format support !!! What will happen ?

What is the common message format nowadays ? PDU or text ? advantages?

I’m new new to this field… please help…

Thanks in advance



“PDU” or “Text” mode just controls the way in which you present the data to the modem - over the air, it is always PDU.

When you select “Text” mode, the modem automatically builds the appropriate PDU for you.


Thanks dude … :slight_smile:

So if we select the text mode ; the module automatically builds the appropriate PDU …
and at the same time the PDU that we are getting from the network will automatically convert to “TEXT format” as in the mobiles right??



Only if it’s a valid text-mode PDU!

The behaviour on receiving a non-text PDU when the modem is in text mode varies - IIRC, Siemens automatically displays it in PDU mode, but Wavecom displays garbage…


valid text-PDU ?

If im sending a text message, say “hello” from a mobile to the wavecom module,
what will be received on the module side ?Is it in PDU format or the modem will automatically decode it to text or should i use any decoding scheme ?

thank you


There is an excellent discussion - with worked examples - of the SMS PDU format here: dreamfabric.com/sms/

And Try playing with the decoders mentioned here: viewtopic.php?f=81&t=4069&p=16215#p16215


I am currently writing program on Q2686. The version of firmware which is loaded on the device is 7.45 .
In the implementation of “SMS Application” I encountered the following problems:
1-First of all when I add the “SMS-PDU Plug-In” to my project and then compile it in “elf mode”,
after programming, the rest of the application doesn’t execute and basically the program doesn’t
even enter the “Main Task”. While the program work properly right before adding the “SMS-PDU Plug-In”.
2-Secondly, as you know, in all the GSM standard characters, for hose symbols which contain two characters,
such as “}” , the first character is 0x27. For instance 0x2741 represents the symbol “}”. However, the GSM module
brings the code 0x2041 instead. Therfore, this causes me problem to find out the content of exact sent SMS.
Such problem exists in “PDU Mode” as well. While in another GSM module which I used for test,
such problem doesn’t occur and the code “0x2041” is exactly generated to represent }.
Please let me be informed if any new version of firmware is available which doesn’t have these two problems.
If not, please give me a solution for my problems.
I am looking forward to hearing from you soon.