Sending a flash SMS message
So far I’ve show how to send a text message in PDU mode. There is nothing special about this.
There are a number of things you can do in PDU mode, that you can’t do in text mode.
A first example is a flash SMS message.
A flash SMS message is an SMS message that, instead of being stored in the SIM or memory of
the receiving phone, pops-up on the receiving phone’s screen, without the user taking any action.
When dismissed the message is usually gone.
Here is an example AT command to send a flash SMS message in PDU mode:
AT+CMGS=28<crlf>
> 0001010B915121551532F40010104190991D9EA341EDF27C1E3E9743<Ctrl-Z>
Here is what the individual octets represent:
Size
Value
Description
1 octet
00
We don’t supply a SMSC number.
1 octet
01
PDU type and options. This is a plain SUBMIT-PDU.
1 octet
01
Our message reference.
1 octet
0B
Size of destination telephone number (in digits)
1 octet
91
International numbering plan.
6 octets
5121551532f4
This represents the destination and it translates to 1 512 555 1234
1 octet
00
Protocol identifier.
1 octet
10
Data Coding Scheme.This is the value that cause the message to be a
flash message as opposed to a standard SMS.
1 octet
10
User Data Length or payload size (in characters).
16
septets
4190991D9E
A341EDF27C
1E3E9743
The payload, also known as User Data. In this case it is just GSM
encoded text.
This particular string represents “A flash message!””
A more elaborate explanation of the GSM encoding and other fields is giving in a previous post
in this series.
