Class ADC – Analog-to-digital conversion

Create object

class ADC.ADC(Pin)

Create an ADC object associated with a set pin. So you can read the analog value on that pin。

• Pin - ADC is available on dedicated pins, ESP32 available pins are：IO39、IO36、IO35、IO33、IO34、IO32. The ADC pins of the control board are P0、P1、P2、P3、P4、P10。

Detailed pin definitions ESP32 pins function list. and :ref:` mPython Board pins definition<mpython_pinout>` chapter。

Example:

from machine import ADC, Pin

adc = ADC(Pin(33))      # create an ADC object

Method

ADC.read()

Read ADC and return read result.

ADC.atten(db)

This method allows setting the amount of attenuation of the ADC input. This allows a wider range of possible input voltages, but at the expense of accuracy (the same number of bits now means a wider range). When atten() is not set, the default is 0DB attenuation. Possible attenuation options include：

• db

ADC.width(bit)

Set the data width (resolution). The resolution of the ADC refers to the precision that can convert the collected analog signal into a digital signal. Usually, we use the “bit” to express, for example, 8 bit means that the ADC can correspond to the voltage signal within the specified range, respectively corresponding to - 2^8-1, that is, 256 digits of 0-255. The higher the resolution digits, the more accurate it can be expressed, and the less information is lost.

• bit - Width options are:

  Macro Definition	Value	Full Range
  ADC.WIDTH_9BIT	0	0x1ff(511)
  ADC.WIDTH_10BIT	1	0x3ff(1023)
  ADC.WIDTH_11BIT	2	0x7ff(2047)
  ADC.WIDTH_12BIT	3	00xfff(4095)

Example:

from machine import ADC, Pin

adc = ADC(Pin(34))      # create an ADC object
adc.atten(adc.ATTN_11DB)   # set 3.3V Range
x = adc.read()
print(x)

Constant

Attenuation ratio

ADC.ATTN_0DB

ADC.ATTN_2_5DB

ADC.ATTN_6DB

ADC.ATTN_11DB

Data width

ADC.WIDTH_9BIT

ADC.WIDTH_10BIT

ADC.WIDTH_11BIT

ADC.WIDTH_12BIT