In order to meet the requirements of industrial control system,an external A/D driver based on SPI bus in Linux system was designed in this paper.In order to load and unload device driverdynamicly,the SPI bus was used to transfer data be-tween A/D and ARM.The application program was used to collect and send data through data processing process and data sending and receiving process.Both achieved synchronization through message queue.It had dynamic loading of equipment and portability. In this way,the control accuracy was not only improved,but also the transmission rate of the buswas improved.The test shows that the design is feasible.%为了满足工业控制系统的测控要求，设计了一种Linux系统下基于SP I总线的外部A/D驱动程序。通过总线设备模型的方法编写驱动程序能动态地加载和卸除设备驱动， A/D和ARM之间通过SP I总线进行数据交互，应用程序通过数据处理进程和数据收发进程进行数据采集计算和传输，两者通过消息队列实现同步。具有设备动态加载、可移植性强等特点，不仅提高了系统转换精度，还提高了总线的传输速率，经测试表明该驱动的设计可行。
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