AD7745是一种响应快速兼超低功耗的高精度电容数字转换器,其采用的通信总线I2C是一种简单双向的两线制同步串行总线,它只需要一根数据线和一根时钟线即可实现连接器件之间的数据传送,但目前广泛应用的51系列单片机均不具有这种接口；文章详细研究了AD7745芯片内部的测量原理及寄存器配置方式,设计了其与单片机的硬件连接电路,使用STC89C52RC单片机的两条普通I/O线,通过软件编程模拟I2C总线所要求的操作时序,实现了对AD7745的控制与数据读取；同时,给出了其中关键程序,调试结果证明了该系统的有效性与稳定性.%AD7745 is the high-precision capacitance-digital converter which is fast response and low power consumption. It uses the communication bus I2 C which is simple two-way and two-wire synchronous serial bus. It uses only a data line and a clock line to make the data transfer between connected devices. But now the 51 series SCM which was widely used didn' t have this kind of interface. This paper studies in detail the measuring principle and register allocation of AD7745 chip, the hardware connection circuit was designed between it and SCM, two general I/ O lines of STC89C52RC SCM were used, use software programming to simulate the operation timing of I2C‘ s re-quest, It is implemented to control AD7745 and read its data. At the same time, the key program was provided. Debugging results demonstrated the effectiveness and stability of the system.
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