本程序代码是使用I2C通信的一个例子，主要实现I2C与在读写模式下的PCF8574通信。-I2C communication with a PCF8574 in read and write mode is

demonstrated. PCF8574 port P is configured with P0-P3 input, P4-P7. Read

P0-P3 input data is written back to Port P4-P7. This example uses the

RX ISR and generates an I2C restart condition while switching from

master receiver to master transmitter.LED toggles inside ISR.