Introduction
Does not need to establish the digit dialing connection based on the GSM short news’s service, only need add on the due-out news the destination address transmission to the short message center, retransmits again from the short message center to the ultimate objective. The GSM short news service is simple by its connection, the expense is inexpensive, the coverage area broad, realized merits and so on convenience to obtain the widespread application. Realizes the long-distance observation reliability using the GSM short news to be high, the signal propagation distance to be far, the cover area is broad, and may save the fishing net initial period the huge investment.
This article to with realized based on the GSM short news receiving and dispatching system’s design has made the concrete description, has given system’s software and hardware design proposal, to the main hardware, namely GSM module Q2403A and 8051 monolithic integrated circuits has made the key introduction. Has given system’s software design, including PC and monolithic integrated circuit correspondence part and short news receiving and dispatching part. Finally realizes the system monitoring function.
The system hardware realizes
Overall system structure
This system hardware mainly by 8051 monolithic integrated circuit expander, the Q2403A handset module, RS-232 parts and so on bus interface electric circuit, power source switch is composed. Figure 1 is the system structure diagram.
Figure 1 system structure diagram
And, the power source switch voltage transforms PC port’s 12V 3.6V and the 5V constant voltage, causes in system’s chip to be at the normal work condition. RS-232 bus interface electric circuit including level switch and serial port expander. after 8051 monolithic integrated circuits realize the memory expands, passes the RS-232 bus interface electric circuit and P
C carries on the data communication; The interrupt mode carries on processing after the data, controls the Q2403A handset module to enter mean action news receiving and dispatching, realizes system’s monitoring function.
Monolithic integrated circuit expander design
Although the MCS-51 monolithic integrated circuit’s interior integrated many resources, these resources are compromise the disposition, the internal program memory, data-carrier storage’s capacity is not big, parallel I/O port’s quantity is not many. In addition, in some applications, the internal timer, the interrupt, the serial port and so on also appears the insufficiency. Therefore, according to the need, this system selects 8051 monolithic integrated circuits and carries on the expansion to it.
The read-write memory expands
This article selects the SRAM chip 6264. The capacity is 8K×8bit. Its address wire has 13, namely A12~A0. 8 data line D7~D0. In addition other pins, altogether some 28 pins, including 2 labelling are the Nc spatial pins. The Nc pin respectively as the address wire A13~A14 use, is the capacity for 16k×8bit and 32k×8bit SRAM memory chip.
The connection plan uses the address to decode completely the design. Uses 74138 decoders for the memory assignment address space which expands. For 6264 data-carrier storage assignment only address space is: 0000H~1FFFH.
The non-erasable storage expands
This article selects AT24C02 to carry on the data storage. It uses two holding wires to carry on the data transmission, one is serial data line (SDA), another is serial clock line (SCL).
RS-232 interface circuit design
MAX202 is the single power source, the double RS-232 transmission/receiver, is suitable in each kind of EIA-232E and the V.28/V.24 correspondence connection. The MAX202 chip has a voltage switch, may transform ±10V the voltage which the input 5V power source the RS-232C output needs, therefore, with this chip connection serial communication system, so long as sole 5V then.
This article selects general asynchronous receive/transmitter MAX3100 to carry on the expansion to the monolithic integrated circuit serial port, is connected the monolithic integrated circuit and the RS-232 main line.
The MAX3100 electric power supply scope width, the power loss low, only absorb 0.5mA in the 2.7V~ 5.5V power source the electric current, has zero power loss engine off pattern, and can awaken by the received signal, uses the SPI/Microwire connection and the main micro controller carries on the correspondence. MAX3100 not only suits in the speed reaches as high as 230kbps RS-232 and the RS-485 data link, moreover the support speed is the 2.4kbps~115.2kbps infrared data association (IrDA)SIR form, in has the good application prospect based on the micro controller’s small system design. Figure 2 is the serial port expansion circuit diagram.
Figure 2 serial port expansion circuit diagram
Power unit
Because the PC port provides the voltage is 12V, in system’s chip has 3.6V and the 5V two kinds. Therefore, the power unit uses American Country Semiconductor Company output voltage adjustable three end integration constant voltage chip LM1085-ADJ.
LM1085 is a model of single chip integration voltage switch. Provides 3 A electric current output, has the overflow protection, the excessively warm protection, has the reliable operating performance, the high working efficiency, can provide stable 3.6V, the 5V voltage for the chip, was the chip work has provided the powerful guarantee. Figure 3 is the power circuit schematic diagram.
Figure 3 power circuit schematic diagram
Handset module part
Q2403A GSM/GPRS module support dual-frequency EGSM/GPRS the 900MHz/1800MHz pattern, supports at instruction, the short news function is complete. The Q2403A module has 60 pin general connections, very easy to integrate in the application product; Has the SIM card confirmation, the power supply, the clock, the replacement and I/O 3V the SIM card connection, including SIMVCC, SIMRST, SIMDATA, SIMCLK and SIMPRES and so on. Moreover, the module provides one to conform to the V24 agreement 6 serial communication connection, including TX, RX, RTS, CTS, DTR, DSR; Simultaneously provides DCD and the RI signal connection, on electrical signal PowerON/OFF and reset signal RST. The module normal work request provides two groups power sources, VBATT provides to the RF part, the voltage range is 3.3V~4.5V, the maximum work rate is 2 W; VDD provides to the baseband part, the voltage range is 3.1V~4.5V, the maximum work rate is 0.5W. Figure 4 is the handset module and the SIM card peripheral circuit design.
Figure 4 handset module and SIM card periphery circuit diagram
System software design
Master routine flow
Master routine primary cognizance system’s initialization, including monolithic integrated circuit clock establishment, port working establishment, serial port establishment (baudrate, interrupt permission and so on), default system data restoration (for example time establishment, flag bit reset and so on), GPRS module initialization, interrupt initialization and so on. Then inquires the SIM card network registration situation repeatedly, until registers successfully. Finally enters the low power loss pattern, the waiting interrupt. Flow as shown in Figure 5.
Figure 5 system master routine flow
PC and monolithic integrated circuit correspondence part
This part including unit operational data’s gathering and the reverse control order’s transmission, completes by serial port RXD/TXD.
PC controller through RS-232 bus transfer many data, data content including unit running status, complete temperature data and input/output state information, as well as breakdown information and so on. In the short news controller’s monolithic integrated circuit judges the data which in the serial port RXD/TXD receive interrupt procedure and processes receives.
Short news receiving and dispatching
This part must realize the function includes: The receive control side sends in the short news and withdraws the effective order word, the assembly control frame; When gathers the urgent breakdown information, perhaps needs to feed back when carries out the result, to the control side transmits the short news. Uses the interrupt mode receive from the Q2403A module information. Figure 6 is the serial port RX/TX receive and the transmission interrupt flow.
Figure 6 serial port RX/TX receive/transmission interrupt flow
The Q2403A support’s function is quite complete, this system has mainly used the short news function. The monolithic integrated circuit and the Q2403A module mainly carries on the correspondence through serial port RX/TX, realizes the receive and the transmission function by at order. With at order mainly has: Inquiry registration condition AT CREG; The short news tabulates AT CMGL; The short news transmits AT CMGS; The short news deletes AT CMGD.
Conclusion
This article in proposed that in overall project design’s foundation, has completed system’s hardware and the software design, the application procedure compilation and the debugging, after the actual movement confirmation, has made the satisfactory progress. Speaking of the present test result, the union long-distance monitoring’s superiority, has the strong usability. Makes the suitable expansion revision after the software and hardware, but may also apply in the environmental monitoring, the petroleum extraction equipment’s monitor and the control, the crops growth condition monitor, the traffic control system and the peaceful against system and so on many domains.
Reference:
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