通道0就是配置的14位
你可以这样理解 21-7=14
相当于将21位右移7位，就变成14位了
看一下下面的图你就明白了



你看一下sm338硬件配置中的scaling功能你就明白了。

把scaling参数的帮助给你发一下，你看一下应该就明白了

Standardization aligns the sensor value to the right; irrelevant positions are removed.

Positions [0 to 12]

This is the number of irrelevant bit positions by which the sensor value is to be shifted to the right.

Steps / revolution

This is the number of steps per revolution of the sensor.
The number of steps per revolution and the sensor type (for example, 13-bit) enable you to automatically calculate the number of irrelevant bit positions by which the sensor value is to be shifted to the right in order to align it.