SPI RTC MAX6902实时时钟的驱动和应用笔记，及其驱动代码，网上很少关于SPI 的，大家参考一下，一定要8个字节一起写。-SPI RTC MAX6902 RTC driver and application notes, and the driver code, on-line small on the SPI, we refer to, we must write 8 bytes together.