nodemcu-firmware/docs/modules/adc.md

ADC Module

Since	Origin / Contributor	Maintainer	Source
2017-04-22	zelll	zelll	adc.c

The ADC module provides access to the in-built ADC1.

On the ESP32 there are two ADC. ADC1 has 8 channels, while ADC2 has 10 channels. Currently, only ADC1 is supported.

adc.setwidth()

The configuration is in effect for all channels of ADC1

Syntax

adc.setwidth(adc_number, bits)

Parameters

• adc_number Only adc.ADC1 now
• bits One of 9/10/11/12.

Returns

nil

adc.setup()

Configuration ADC1 capture attenuation of channels

Syntax

adc.setup(adc_number, channel, atten)

Parameters

• adc_number Only adc.ADC1 now
• channel When using adc.ADC1: 0 to 7. 0: GPIO36, 1: GPIO37, 2: GPIO38, 3: GPIO39, 4: GPIO32, 5: GPIO33, 6: GPIO34, 7: GPIO35
• atten One of following constants
  • adc.ATTEN_0db The input voltage of ADC will be reduced to about 1/1 (1.1V when VDD_A=3.3V)
  • adc.ATTEN_2_5db The input voltage of ADC will be reduced to about 1/1.34 (1.5V when VDD_A=3.3V)
  • adc.ATTEN_6db The input voltage of ADC will be reduced to about 1/2 (2.2V when VDD_A=3.3V)
  • adc.ATTEN_11db The input voltage of ADC will be reduced to about 1/3.6 (3.9V when VDD_A=3.3V, maximum voltage is limited by VDD_A)

Returns

nil

adc.read()

Samples the ADC. You should to call setwidth() before read().

Syntax

adc.read(adc_number, channel)

Parameters

• adc_number Only adc.ADC1 now
• channel 0 to 7 for adc.ADC1

Returns

the sampled value (number)

Example

val = adc.read(adc.ADC1, 0)