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Firmware & API Reference
SG Modules
Machine
ADC

ADC

class ADC – Analog to Digital Conversion

Quick Usage Example

import machine

adc = machine.ADC()             # create an ADC object
apin = adc.channel(pin='P16')   # create an analog pin on P16
val = apin()                    # read an analog value

Constructors

class machine.ADC([id=0] )

Create an ADC object; associate a channel with a pin. For more info check the hardware section.

Methods

adc.init([bits=12])

Enable the ADC block. This method is automatically called on object creation.

  • bits can take values between 9 and 12 and selects the number of bits of resolution of the ADC block.

adc.deinit()

Disable the ADC block.

adc.channel(pin, attn=ADC.ATTN_0DB)

Create an analog pin.

  • pin is a keyword-only string argument. Valid pins are P13 to P20.
  • attn is the attenuation level. The supported values are: ADC.ATTN_0DB, ADC.ATTN_2_5DB, ADC.ATTN_6DB, ADC.ATTN_11DB

Returns an instance of ADCChannel.

adc.vref(vref)

If called without any arguments, this function returns the current calibrated voltage (in millivolts) of the 1.1v reference. Otherwise it will update the calibrated value (in millivolts) of the internal 1.1v reference.

adc.vref_to_pin(pin)

Connects the internal 1.1v to external GPIO. It can only be connected to P22, P21 or P6. It is recommended to only use P6 on the WiPy, on other modules this pin is connected to the radio.

Constants

  • ADC channel attenuation values: (value references are approximations)
    • ADC.ATTN_0DB: 0dB attenuation. 1V will be registered as 1V
    • ADC.ATTN_2_5DB: 2.5dB attenuation. 1V will be registered as 0.75V
    • ADC.ATTN_6DB: 6dB attenuation. 1V will be registered as 0.5V
    • ADC.ATTN_11DB: 11dB attenuation. 1V will be registered as 0.3V

Note: The voltages will automatically be corrected by adcchannel.voltage()

Class ADCChannel – created upon initialisation of an ADC Channel

The following methods can be applied on the adcchannel() instance. ADC channels are created using the ADC.channel(...) method.

adcchannel()

Fast method to read the channel value.

adcchannel.value()

Read the channel value.

adcchannel.init()

(Re)init and enable the ADC channel. This method is automatically called on object creation.

adcchannel.deinit()

Disable the ADC channel.

adcchannel.voltage()

Reads the channels value and converts it into a voltage (in millivolts)

adcchannel.value_to_voltage(value)

Converts the provided value into a voltage (in millivolts) in the same way voltage does.

ADC pin input range is 0-1.1V. This maximum value can be increased up to 3.3V using the highest attenuation of 11dB. Do not exceed the maximum of 3.3V, to avoid damaging the device.