VC + + Serial programming of SMS application development

Several previous series we explained the hardware principle of serial communication, the DOS platform control and the serial port programming based on WIN32 API, control and third party. As the last serial of this series, this chapter will give a typical application example: Siemens SMS Service Module TC35 serial control.

1. SMS Control Terminal

As SMS (Short message service,sms) a clan, presumably you have this experience: use mobile phone to edit short messages is very inconvenient, error prone, and modify time, if you can use the computer to send and receive text messages is more convenient. Note that this text of the use of the computer to send and receive text messages is not said through the "NetEase SMS King" and other ways to send and receive text messages on the Internet, but directly with the computer to control the operation of the GSM communication system of the message terminal to send and receive, so the principle of sending and receiving text

In fact, a lot of junk text messages are also used by this message terminal sent out!

Let's introduce a GSM module, it is the TC35 of Siemens, which consists of GSM baseband processor, power supply ASIC, RF circuit and flash memory, which is responsible for processing the audio, data and signal in GSM cellular equipment, and the embedded software part performs the function of application interface and all GSM stack. TC35 supports Chinese short message, works in EGSM900 and GSM1800 dual band, power range is 3.3~5.5v, can transmit voice and data signal, consumes power in EGSM900 (class 4) and GSM1800 (1 classes) respectively 2W and 1W, The SIM card reader and the antenna are connected by an interface connector and an antenna connector respectively. TC35 Data Interface (CMOS level) through the AT command can be two-way transmission of instructions and data, the optional baud rate of 300bit/s~115kbit/s, automatic baud rate of 1.2k~115kbit/s. It supports both text and PDU formats, and can be restarted and failback through the AT command or turn-off signal.

We need to use the TC35 modular hardware to form a TC35 terminal equipment, and the computer through the RS-232C serial connection, and its own production on the PC running SMS transceiver software, you can form a short message transceiver system. The TC35 terminal circuit is shown in the following illustration:

TC35 control mainly includes the following types of instructions:

(1) Initialization instructions

Set the short message send format At+cmgf=1<cr>, set 1 to represent the PDU mode,<cr> is the carriage return symbol, namely 0x0d, the instruction is correct the module returns <CRLF>OK<CRLF>,<CRLF > is the carriage return line symbol.

(2) Set/Read Short Message Center

The short Message center number is provided by the mobile operator.

The directive format for setting up a short message center is:

At+csca=″+8613800531500″ (Short Message Center) <CR>

Set the correct module to return to <CRLF>OK<CRLF>.

Reading a short Message Service center uses the command:

At+csca=?<cr>

The TC35 module should return:

<CRLF>+CSCA:″8613800531500″<CRLF>.