PDU for sending with AT commands in GSM modems.

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SMS & MMS Technical Forum » NowSMS Support - SMS Issues (Product Support Only) » Archive through March 09, 2004 » PDU for sending with AT commands in GSM modems. « Previous || Next »
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Shrirang Khare
New member
Username: Shrirang

Post Number: 1
Registered: 12-2003
Posted on Wednesday, February 25, 2004 - 04:18 pm:   

Hi ,

In some GSM modems we need to specify a 00 in beginning of the PDU to tell the modem, that pick the SMSC address from the phone. Now the question is should this 00 contribute to the TPDU length? for example :---

cmgs=16
0035010C9119892255100300000B02E834

Here 16 is the length of the TPDU excluding the preceding 00 now this length can be 17 or 16.
For some devices the length of preceding 00 is required and in others its not}

Why does this happen ?

Thanx in Advance
Shrirang.
Bryce Norwood - NowSMS Support
Board Administrator
Username: Bryce

Post Number: 2007
Registered: 10-2002
Posted on Tuesday, March 09, 2004 - 05:05 pm:   

ETSI GSM 07.05, in its definition of the +CMGS command in PDU mode, Section 4.3, states:


quote:

<length> must indicate the number of octets coded in the TP layer data unit to be given (i.e. SMSC address octets are excluded)




I have not encountered any modems that expected the length to include the SMSC address parameter, but that is not to say that there are not GSM modems out on the market that did not implement this feature correctly. (Hopefully there are firmware updates available for any modems that have this bug.)

-bn

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