linux下S3C2440控制PCF8591，读取4通道数据并计算平均值。关键点是，每次读取必须抛掉第一个数据，有效数据从第二个算起-S3C2440 linux under control PCF8591, 4-channel data read and calculate the average. The key point is that each read data to discard the first valid data from the second counting! ! !