FM1702SL射频芯片对外接口为SPI总线方式，对FM1702的操作实际上就是通过SPI总线

对FM1702SL内部的相关寄存器进行读写操作，从而实现射频读/写卡功能。本驱动程序基于

FM2306A编写(兼容PIC指令集的其他MCU也同样试用)，通过IO口软件模拟SPI总线时序。-The external interface of the RF chip　FM1702SL SPI bus way the FM1702 operation is actually through the SPI bus　of FM1702SL internal register read and write operations, enabling RF read/write card function. The driver is based on writing (compatible PIC instruction set MCU also the same trial)　FM2306A, through IO port software simulation SPI bus timing.