Gsm module circuit diagram

With the development of communication technology, the service function based on mobile communication network is expanding in the field of industrial control and remote control. In order to meet this demand, Siemens introduced a new generation of wireless communication GSM module TC35i. Based on the short message function of this module, the function of user information processing can be realized quickly, safely and reliably, especially when the control center is far away from terminal equipment or it is inconvenient to use wired communication media. The system consists of a control center and several display screens. The control center sends the latest information to each display screen in real time, forming a communication link between the control center and the display screen.

Hardware Interface Circuit between 2 TC35i and Single Chip Microcomputer

TC35i can realize data, voice transmission, short message service and fax quickly, safely and reliably in the system scheme. The working voltage of the module is 3.3 V~5.5 V, and it can work at 900 MHz ~ 1800 MHz. The module has AT command set interface and supports short messages in text and PDU mode. In addition, the module also has the functions of phone book, multi-party call, roaming detection and so on. Common working modes are power saving mode, I-DLE and talking. Through the 40-pin ZIF connector, the bidirectional transmission of power connection, instructions, data, voice signals and control signals can be realized. The SIM card holder and antenna can be connected by ZIF connector and 50Ω antenna connector respectively.

In the control system, AT89C5 1 single chip microcomputer is used to expand RAM6264, and at the same time, 128 B data corresponding to the display screen and information read from GSM module are stored. In order to increase the data storage capacity, this design adopts AM29F040 Flash Memory (512kb), which has the advantages of large storage capacity, high integration, low cost, flexible reading and writing, and good data non-volatility. It has 15 address lines, in which the low 8-bit address is latched by 74HC373 and provided by P0 port, and the high 1 1 bit address is connected with P 1.4, P 1.5 and P1.6 by P2 port. 8-bit data is directly provided by PO port.

Adopting dynamic scanning mode, scanning 16 line by line with 74HCl54 and 74HC595, and using the persistence effect of human vision, I/O resources are saved and calorific value is reduced.

3 working principle

As shown in Figure L, at the receiving end, MCU reads the data carried by TC35i module in the form of short message, and displays it on the LED display screen after processing. Because the Chinese characters in the short message only have 1 code, the single chip microcomputer application system must configure the Chinese character font and convert the code into Chinese character dot matrix data. Therefore, when designing the single chip microcomputer application system, the control center edits the PDU data packet and adopts the user-defined data mode. Among them, the data representing Chinese characters directly use the built-in codes of Chinese characters, and the font configured by the system is GB-23 12 coded Chinese font, that is, the position code Chinese font. The following introduces the data format of SMSPDU by analyzing the information to be sent stored in the mobile phone. First, write a message on your mobile phone. Send the mobile phone number as 1360569603 1 and the message content is "HelloWorld!" . This message can be read by executing AT+CMGL=2. The operation process is as follows (italicized characters are response information, {} is comments): The software interface between the microcontroller and the mobile phone is actually the technology that the microcontroller controls the mobile phone through at instructions related to GSM short messages, such as reading the content of the mobile phone short messages, deleting the content of the short messages, and listing unread short messages in the mobile phone. The execution of the l instruction is not as simple as some information introduced. In fact, the execution of instructions needs to be completed through the interaction between single chip microcomputer and mobile phone, and the number of bytes sent or received at a time is strictly regulated. They must exchange data according to these regulations, otherwise, communication will fail. Table l lists the execution process of AT instruction. All instruction symbols, constants and PDU data packets of AT instruction are transmitted in ASC II encoding form, for example, ASC II encoding of "A" is 4 1H, ASC II encoding of "T" is 54H, and ASC II encoding of number "0" is 30H. In order to control the work of the mobile phone, the single chip microcomputer must set the short message working mode of the mobile phone to PDU format, that is, it is completed by the instruction AT+CMGF=0. After sending each L command to the mobile phone, the microcontroller must end the command with enter, and the ASC code of enter is ODH. For example, the microcontroller sends an instruction "AT+CMGF=0" to the mobile phone, and its ASC codes are listed as "4 1H, 54H, 2BH, 42H, 4DH, 47H, 46H, 3DH, 30H, 06h. When the mobile phone receives a complete AT command, the mobile phone does not execute the command immediately, but sends all ASC Ⅱ coding sequences (including ODH) of the just received AT command in reverse, then sends ASC Ⅱ codes of 1 carriage return and line break, namely 0DH and OAH, and finally executes the command. When a mobile phone sends a short message to a single chip microcomputer, the content of its PDU packet is data expressed in the radix of 16, but instead of directly transmitting the radix of 16 to the single chip microcomputer, every bit of the radix of 16 is still sent as ASC II code, so that the radix of 16 of 2 bytes becomes ASC II code of 4 bytes. However, the data byte length in PDU packet is still the actual byte length, not the byte length that becomes ASC code, so special attention should be paid when programming, otherwise the received data will be incomplete. After receiving the PDU packet, MCU must restore it to 16 base data. The algorithm is as follows: Let A be the received ASC code and B be the converted 16 radix. Then, if one