问题2:开启输入缓冲buffer后,发现ADS1256无法测取到满量程(满量程5V,只能测到3.5V左右),关闭缓冲后问题就得到解决。
手册中在模拟输入缓冲小节有提到这部分内容With the buffer enabled, the voltage on the analog inputs with respect to ground (listed in the Electrical Characteristics as Absolute Input Voltage) must remain between AGND and AVDD − 2.0V. Exceeding this range reduces performance, in particular the linearity of the ADS1255/6.
也就是说当开启输入缓冲时,模拟输入端的电压在AGND - AVDD-2才能准确测量,超过这个范围测量值就会不对。
问题2应该时和这个原因有关。