提供I2C总线初始化、工作时的启始位、结束位、提供I2C总线的时钟信号，并返回在时钟电平为高期间 SDA信号线上状态。本函数可用于数据发送，也可用于数据接收-provide I2C bus initialization, the Start-end, provide the I2C bus clock signal, the clock and return to the high-level signal line during the SDA state. This function can be used to transmit data, can also be used for data reception