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analogReadResolution()

[Zero, Due & MKR Family]

Description

analogReadResolution() is an extension of the Analog API for the Zero, Due, MKR family, Nano 33 (BLE and IoT) and Portenta.

Sets the size (in bits) of the value returned by analogRead(). It defaults to 10 bits (returns values between 0-1023) for backward compatibility with AVR based boards.

The Zero, Due, MKR family and Nano 33 (BLE and IoT) boards have 12-bit ADC capabilities that can be accessed by changing the resolution to 12. This will return values from analogRead() between 0 and 4095.
The Portenta H7 has a 16 bit ADC, which will allow values between 0 and 65535.

Syntax

analogReadResolution(bits)

Parameters

bits: determines the resolution (in bits) of the value returned by the analogRead() function. You can set this between 1 and 32. You can set resolutions higher than the supported 12 or 16 bits, but values returned by analogRead() will suffer approximation. See the note below for details.

Returns

Nothing

Example Code

The code shows how to use ADC with different resolutions.

void setup() {
  // open a serial connection
  Serial.begin(9600);
}

void loop() {
  // read the input on A0 at default resolution (10 bits)
  // and send it out the serial connection
  analogReadResolution(10);
  Serial.print("ADC 10-bit (default) : ");
  Serial.print(analogRead(A0));

  // change the resolution to 12 bits and read A0
  analogReadResolution(12);
  Serial.print(", 12-bit : ");
  Serial.print(analogRead(A0));

  // change the resolution to 16 bits and read A0
  analogReadResolution(16);
  Serial.print(", 16-bit : ");
  Serial.print(analogRead(A0));

  // change the resolution to 8 bits and read A0
  analogReadResolution(8);
  Serial.print(", 8-bit : ");
  Serial.println(analogRead(A0));

  // a little delay to not hog Serial Monitor
  delay(100);
}

Notes and Warnings

If you set the analogReadResolution() value to a value higher than your board’s capabilities, the Arduino will only report back at its highest resolution, padding the extra bits with zeros.

For example: using the Due with analogReadResolution(16) will give you an approximated 16-bit number with the first 12 bits containing the real ADC reading and the last 4 bits padded with zeros.

If you set the analogReadResolution() value to a value lower than your board’s capabilities, the extra least significant bits read from the ADC will be discarded.

Using a 16 bit resolution (or any resolution higher than actual hardware capabilities) allows you to write sketches that automatically handle devices with a higher resolution ADC when these become available on future boards without changing a line of code.