`machine.ADC` – Functions to control the nRF ADC

The machine.ADC class contains all of the functions to control the nRF52 ADC. Import it using

from machine import ADC

To see what’s contained inside the class you can use the help() command

help(ADC)

Constructor

class machine.ADC(channel, pPin, res=14[bit], samp=32, pRes=PULL_DISABLED, nRes=PULL_DISABLED, gain=GAIN_DIV6, ref=REF_INTERNAL, acq=10[us], mode=MODE_SINGLE)

The S1 module breaks out two nRF GPIO pins. PIN_A1 and PIN_A2. Both of these pins can be used as ADC inputs, either as two single ended inputs, or a differential pair

To initialize an ADC input pin, call the ADC constructor

  myPin = ADC(0, ADC.PIN_A1) # Channel 0, and pin A1

The channel can be from 0 - 6. Different channels can be set using the same pin for different configurations. To fully understand the ADC features and limitations, have a look at the SAADC section of the nRF52811 datasheet

To view the current configuration, you can simply print the object

  myPin
  # Prints out the configuration for myPin
  ADC(ch=0, pPin=PIN_A1, res=14[bit], samp=32, pRes=PULL_DISABLED, nRes=PULL_DISABLED, gain=GAIN_DIV6, ref=REF_INTERNAL, acq=10[us], mode=MODE_SINGLE)

Various options can be provided when setting up the ADC pin

res
`14`	Uses a 14 bit ADC resolution. Default
`12`	Uses a 12 bit ADC resolution
`10`	Uses a 10 bit ADC resolution
`8`	Uses an 8 bit ADC resolution

samp
`1`	No oversampling
`2`	Use 2x oversampling
`4`	Use 4x oversampling
`8`	Use 8x oversampling
`16`	Use 16x oversampling
`32`	Use 32x oversampling. Default
`64`	Use 64x oversampling
`128`	Use 128x oversampling
`256`	Use 256x oversampling

pRes/nRes	Note: nRes is only applicable in differential mode
`PULL_DISABLED`	Internal pull resistor is disabled. Default
`PULL_UP`	Pin will be pulled up
`PUUL_DOWN`	Pin will be pulled down
`PULL_HALF`	Pin will be pulled to half the VDD of the nRF (1.8V/2)

gain
`GAIN_DIV6`	Set the ADC gain to 1/6. Default
`GAIN_DIV5`	Set the ADC gain to 1/5
`GAIN_DIV4`	Set the ADC gain to 1/4
`GAIN_DIV3`	Set the ADC gain to 1/3
`GAIN_DIV2`	Set the ADC gain to 1/2
`GAIN_UNITY`	Set the ADC gain to 1
`GAIN_MUL2`	Set the ADC gain to 2
`GAIN_MUL4`	Set the ADC gain to 3

ref
`REF_INTERNAL`	Use the internal 0.6V reference. Default
`REF_QUARTER_VDD`	Use a 1/4 VDD reference ~1.8V/4

acq
`3`	Use an acquisition time of 3us
`5`	Use an acquisition time of 5us
`10`	Use an acquisition time of 10us. Default
`15`	Use an acquisition time of 15us
`20`	Use an acquisition time of 20us
`40`	Use an acquisition time of 40us

mode
`MODE_SINGLE`	Use the pin as a single ended input. Default
`MODE_DIFF`	Enable differential input. The other pin will be automatically selected as the negative input

Functions

ADC()

Gets the raw integer register value of the ADC channel
```
  myPin()
  # Returns the raw value
  399
```

ADC.voltage()

Gets the ADC value and returns the voltage as a float based on the channel settings
```
  myPin.voltage()
  # Returns the voltage as a float
  0.1010742
```

ADC.calibrate()

Internally calibrates the ADC for more accurate readings. Can be called after power on, or periodically if the module will be subject to large temperature changes

machine.ADC – Functions to control the nRF ADC

Constructor

Functions

`machine.ADC` – Functions to control the nRF ADC