【導(dǎo)讀】款家用的可燃?xì)怏w報(bào)警系統(tǒng)。此系統(tǒng)主要由單片機(jī)最小系統(tǒng)；天然氣檢測(cè)電路；數(shù)碼管顯示電路；遠(yuǎn)程報(bào)警和聲光。此系統(tǒng)能有效檢測(cè)環(huán)境中可燃?xì)怏w的濃度，一旦其濃度超出報(bào)警限定值，就能發(fā)出聲光報(bào)警信號(hào)，開。啟換氣裝置，并且能隨著濃度的增加報(bào)警音量逐漸增大，同時(shí)實(shí)現(xiàn)遠(yuǎn)程報(bào)警，能及時(shí)起到安全防范的作用。

　　

【正文】 Mobile Communications[J].2020:64. [14]Gee,Aggelou Jan. An integrated platform for ad hoc GSM cellular munications[J].2020:189. 陜西理工學(xué)院畢業(yè)論文（設(shè)計(jì)） 第 26 頁 共 43 頁 附錄 A The Design and Implementation of A Wireless Data Transceiver Abstract—We designed a wireless data transceiver which is based on ATMEGA128 controller and SIM900A. By using the SIM900A chip, it can send data wirelessly through GSM/ GPRS, and by using the ATMEGA128 controller, it can process the data, order and control SIM900A, and then we can transfer data to the remote terminal wirelessly. According to a large number of experiments, we know that: this system is stable, at low cost, easy to take the secondary development, and it will be applied widely in the further. Keywords—SIM900A。 ATMEGA128。 data transceiver。 GSM/GPRS INTRODUCTION Currently, most of the data transceiver is used by cable or slot widely, by the limited of insufficient number of slots, inconvenient installation, the transmission distance and some other factors, with the development of wireless munication, the wireless data transceiver emerged slowly because it is simple to use and flexible distributing. This has bee an important new development direction of data transceiver. And the success of the SIM900A chips in numerous project implementation provides a new idea for wireless data transceiver. Therefore, in order to meet the new requirements of more and more users, we designed the wireless data transceiver based on SIM900A and ATMEGA128 single chip which is at low power consumption. This system supports to transmit data to the specified terminal through GSM or GPRS, and there is almost no limited to the geographical constraints. This system supports to set threshold and search information by mobile phone users。 it also can send alarm message according to the threshold of environmental parameters which is set by the users. Besides, it also supports balance reminded, when the balance of SIM cards in system are insufficient, it will remind users to recharge by the way of sending short message, this measure can prevent the system from economic loss caused by the price problem. THE OVERALL DESIGN OF THE WIRELESS DATA TRANSCEIVER This system is posed of the main control module, the wireless munication module, the power supply module, the serial port module and so on. The main control module uses ATMEGA128 as its main control chip, we select it mainly to parse the external terminal mand and control SIM900A to implement the corresponding mand through the AT mand。 The wireless munication module mainly uses the SIM900A chip made by SIMCOM pany as its core chip, and we use this module mainly to send the data to the specified terminal wirelessly and receives the terminal SMS mands。 The power supply module mainly uses LM2576 and MIC29302 regulator chip, they provide stable 5V and power supply for the system respectively。 The serial port circuit is used to realize the munication between MCU and puter. Through the JTAG interface and ISP interface, we can configure the fuse of MCU and program it. In addition, two of the ATMEGA128 IO ports are used to reset or restart the SIM900A. THE HARDWARE CIRCUIT DESIGN OF THE WIRELESS DATA TRANSCEIVER According to the overall structure of this system, the hardware circuit mainly contains following modules: the main control module, wireless transceiver module, and the power supply module. THE DESIGN OF THE MAIN CONTROL MODULE ELECTRIC CIRCUIT We selected ATmega128 MCU as the main control chip of the main control module. ATmega128 is an 8 陜西理工學(xué)院畢業(yè)論文（設(shè)計(jì)） 第 27 頁 共 43 頁 bit single chip microputer produced by ATMEL Company which is made by lowpower COMS based on AVR RISC. It has two ways of UART which can be programmed. AVR kernel sets the 32 working registers and a rich instruction together. The kernel performs an instruction and accesses two independent registers in an AT clock cycle. ATmega128 will analysis the receive mand and pack the data which will be sent. Through the second serial port, ATmeag128 will operate the wireless munication module to send packets out by using the AT mand. Through the first serial port, it will send the realtime information to the PC to display at the same time. THE WIRELESS TRANSCEIVER MODULE CIRCUIT DESIGN We selected SIM900A module made by SIMCOM Company to realize the wireless munication module circuit. SIM900A is a dual band GSM/GPRS module and it is specially designed for the Chinese mainland market. Its working frequency is EGSM900MHz and DCS1800MHz. The embedded TCP/IP protocol is very useful when we use it to send data . The GSM/GPRS munication made up of SIM900A chip, antenna, matching circuit for antenna impedance, SIM card circuit, ESD protection circuit and some other circuit. Among them, SIM900A municates with the ATMEGA128 through the serial port。 the ESD electrostatic protection circuit can protect the data of SIM card by using the SMF05C chip。 under the help of APPCAD simulation software, we designed the 50 transmission line for the impedance matching circuit to ensure the signal strength. In addition, we selected Molex 91228 SIM card seat as the SIM card seat, this measurement can prevent the system from data transmission failure which causes by the bad contact of SIM card with the card seat. THE DESIGN OF THE POWER MODULE CIRCUIT There are two modules which need power supply in this system: the main control module and SIM900A wireless module. And the main control module needs the DC5V power and wireless module needs power. At the same time, the power supply must provide sufficient current to the 2A to ensure that voltage will not drop when the wireless module sends data. We selected to provide 5V voltage for this system, and selected LM29302 to provide for this system. The regu