How to send SMS by GSM modem in PDU mode?

Question

I want to send SMSs in PDU mode. I have checked the spec for my modem, and it supports PDU mode.

I have developed a PDU encoder and decoder, but now I do not know how to send data to my modem. I tried these AT commands:

AT

AT+CMGF=0

after sending these commands I sent the PDU data like this:

AT+CMGW="16079189390500410011000C918939050000000000AA02E834" 

I have checked the correctness of this PDU using this online tool :

http://www.twit88.com/home/utility/sms-pdu-encode-decode

but after sending it via the AT command, the modem hangs.

Is this the right way to send SMS PDUs? I searched on Google and can not find useful information.

Answer 1

First of all, to send sms when modem is in pdu mode, you must send these commands: AT+CMGS=<length> <CR>, where length is (length of PDU binary string - 2) / 2. When '>' symbol appears you must send your pdu and ctrl+z character (char.ConvertFromUtf32(26)).

Here are some resources that may be useful: http://www.developershome.com/sms/ SMS Tutorial http://www.diafaan.com/sms-tutorials/gsm-modem-tutorial/online-sms-deliver-pdu-decoder/ another online pdu decoder (but your link is better in my opinion) http://www.fccps.cz/img.asp?attid=24590 AT commands guide (for wavecom, but there is no difference)

Last advice - use any telnet client to connect and test your modem and see how it responds

Answer 2

length of PDU string = ( PDUlength - 2 - ServiceCentreNumber length ) / 2

ServiceCentreNumber length is first byte of PDU string. (2 Hex char = 8 bit)

Command for send sms in PDU mode:

send:AT+CMGF=0                 //recieved "\r\nOK\r\n"
send:AT+CMGS=<length>          //recieved "\r\n> "
send:<pdu string><char(26)>    //recieved "\r\n+CMGS: 59\r\n\r\nOK\r\n"

Another variant is to use instead +CMGS command +CMGW to write msg to memory (code same above) and then use +CMSS to send the message from memory.