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How to analyze the alternative interpretation of the sampling principle, I believe that many inexperienced people do not know what to do about it. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

We know that single-chip microcomputer is a digital chip, which only knows the logical sequence composed of 0 and 1, but in reality, there are many analog physical quantities, such as temperature, how to deal with these analog quantities by the single-chip microcomputer system, this will use AD conversion, AD conversion of English is Analog to Digital, converted from analog to digital; and DA, is Digital to Analog, digital is converted into analog. So how does the single-chip microcomputer realize the transformation?

The data manual on the AD converter chip will tell you a message: this chip is 8-bit, this chip is 10-bit, there are 12-bit, 16-bit. This represents the maximum value that single-chip microcomputer AD can get after sampling. How to AD sampling when the corresponding value of 8 bits is 0-255, the corresponding value of 10 bits is 0-1023, the corresponding value of 12 bits is 0-4095. For a 12-bit AD conversion chip, if the input voltage is 0, then the single-chip microcomputer read is 0, if the input voltage is VCC, then the single-chip microcomputer read is 4095, already know these two points (0 score 0), (VCC,4095), according to two points can determine a formula, at this time you can find out any voltage value corresponding to the number of how much.

There is also an important concept is the reference voltage, generally speaking, the reference voltage can not exceed the supply voltage of the single-chip microcomputer. Why can't the reference voltage directly take the power supply voltage of the single-chip microcomputer? if you use the external meter to measure the power supply voltage of the single-chip microcomputer, you will find that it is not always 5V or 3.3V, but it may be 4.95V 5.01V or 3.29V 3.312V. When the accuracy of AD sampling results is not high, VCC can be used as the reference voltage. But for high-precision instruments, a reference with a very stable voltage value is needed, such as the reference voltage chip LM4040-3.3V (output 2.5V).

Some multi-pin chips, such as STM32's MCU with more than 100 pins, have separate reference voltage pins. And the single-chip microcomputer with few pins, such as LPC11C14 only has 48 pins, the reference voltage pin is not alone, you can connect the reference voltage directly to the VCC, or you can use a separate reference voltage as the reference voltage, but the voltage difference between the reference voltage and VCC can not exceed 0.3V, otherwise the single-chip microcomputer will not work.

After reading the above, have you mastered the alternative interpretation method of how to analyze the sampling principle? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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