PDU mode is a lot more interesting than text mode. There are all kinds of things that can be done with SMS messages, all leveraging special formatting that is only available if you use PDU mode:
The formatting of these PDU’s is a little more complicated and requires some bit manipulations that are hard to do by hand.
The GSM modem is put into PDU mode with the command ‘AT+CMGF=0’. Once in PDU mode a PDU can be sent using the ‘AT+CMGS’ command:
As explained in a prevous post in this series, a GSM modem can let you send SMS messages from a PC. There are two basic ways to do this: text mode and PDU mode.
You can play around with your GSM modem using a terminal program like HyperTerminal (which came with Windows XP, but is no longer there in Windows Vista). The commands I mention can just be entered in the terminal window when connected to the modem. You can try the following basic commands, any modem should support these:
||Returns general modem identification
||Dials the phone number you supplied (don’t enter the <> brackets)
||Hang-up the phone (useful after the previous command).
The following commands are specific for GSM modems. If you get an error response (e.g. ‘+ERR’), your modem probably isn’t a GSM modem or it doesn’t support the extensions specific for GSM modems. Read More…
Sending an SMS from a PC to a GSM phone can be done in many ways.
The first method I discuss requires a GSM phone attached to your PC.
The GSM phone (or GMS card) can be connected to your PC in different ways; using BlueTooth, infrared (IrDA) or a serial cable. The way the phone is connected is irrelevant, what counts is that the GSM is available as a modem. On windows PCs this means that it will be available as a TAPI modem.
Programs make modems do things by sending them so called AT commands. E.g.
ATD5551234 makes the modem dial a connection to the number 5551234.
ATA makes the modem answer an incoming call. All your modem’s features are available using commands like these.