PCF8591是8bit的A/D和D/A芯片，采用i2c接口，它有四路模拟输入口和一个模拟输出口，采样速率取决于i2c的速率。数据传输是高位在前低位在后（不论是主机写入数据，还是主机读取的数据）。-PCF8591 is the 8bit A/D and D/A chip, using i2c interface, which has four analog inputs and one analog output sampling rate depends on the rate of i2c. Data transmission is high after the previous low (either host-write data, or data read by the master).