说明：  本篇文章详细介绍了RS-485/422原理与区别，元件选择，参考电路，通讯规约，程序设计等方面的应用要点，以及在产品实践中总结出的一些经验和窍门
(This article details the difference between theory and RS-485/422, component selection, reference circuits, communications Statute, program design, such as the application of the main points, as well as practice in the product sum up some experiences and tips)