---
title: "ADC"
aliases:
    - firmwareapi/pycom/machine/adc.html
    - firmwareapi/pycom/machine/adc.md
    - chapter/firmwareapi/pycom/machine/adc
---

## class ADC – Analog to Digital Conversion


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### Quick Usage Example
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```python
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] {{% development version="" style="inline" %}}hello  {{% /development %}})

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.