Design Of A CPU-card-based Prepaid Gas Meter

Most gas meters use logic encryption card at present.Logic encryption card has password protection and can provide a certain security,.but the type is various.The card don’t have uniform standard and compatibility is poor.When people rewrite the logic encryption card,they have to check the password.The password appears in plain text,.It’s easy to be intercepted by outside.So the whole system is easy to leak the password and produce pseudo card.Moreover,the password algorithm is controlled by the gas meter manufacturer,.The gas sales company cannot grasp the core security alone.To solve the above problem, this paper research a prepaid gas meter based on CPU card.The main contents of the research are as follows:In the hardware, the whole system use 16-bit ultra-low power microcontroller MSP430F4152 as the central processor,with the addition of a series of low-power peripheral circuits.The hardware include CPU card module, CPU card interface module,LCD module, ESAM module, power supply voltage monitoring module, valve control module and flow detection module.If the whole external circuit can achieve their functions,then optimize the external circuit.The I/O ports should put in a reasonable allocation in order to reduce the power of the hardware circuit. The anti-interference ability of the hardware platform will be enhanced.In the software, the gas meter of smart CPU card use IAR Embedded compiler environment as the software development environment. In this compilation environment,all the program use C language to write. The whole system use modular program design method in order to make different subroutines to perform different functions. Software part include main program design, CPU card operation process design, internal certification program design, external certification program design,supply voltage monitoring module programming design, flow detection module programming design and valve control module program design.In the PC software, developing the the PC software of external certification system, internal certification system,issuing gas system and purchase gas system.The PC software fully consider prepaid industry problems.The function is complete.The whole system will provide a good trading platform to users.The whole system accomplish the debugging of the software and hardware and conduct reliable test, achieving the function of internal authentication, external authentication, the information exchange between smart gas meter and CPU card, the drive of LCD circuit and valve circuit, flow detection and prepayment.