analogWrite()

Description

Writes an analog value (PWM wave) to a pin. Can be used to light a LED at varying brightness or drive a motor at various speeds. After a call to

analogWrite()

analogWrite()

digitalRead()

digitalWrite()

Check your board pinout to know which are the officially supported PWM pins. While some boards have additional pins capable of PWM, using them is recommended only for advanced users that can account for timer availability and potential conflicts with other uses of those pins.

In addition to PWM capabilities some boards have true analog output when using

analogWrite()

DAC

Only 4 different pins can be used at the same time. Enabling PWM on more than 4 pins will abort the running sketch and require resetting the board to upload a new sketch again.

You do not need to call

pinMode()

analogWrite()

analogWrite

analogRead

Syntax

Use the following function to generate a PWM signal on a given pin:

analogWrite(pin, value)

Parameters

The function admits the following parameters:

• pin

  : the Arduino pin to output the PWM signal. Allowed data types:

  int

• value

  : the duty cycle: between 0 (always off) and 255 (always on). Allowed data types:

  int

Returns

The function returns nothing.

Example Code

Sets the PWM duty cycle that controls the LED proportional to the value read from the potentiometer (connected to A3).

1int ledPin = 9;      // LED connected to digital pin 9
2int analogPin = A3;   // potentiometer connected to analog pin 3 (A3)
3int val = 0;         // variable to store the read value
4
5void setup() {
6  pinMode(ledPin, OUTPUT);  // sets the pin as output
7}
8
9void loop() {
10  val = analogRead(analogPin);  // read the input pin
11  analogWrite(ledPin, val / 4); // analogRead values go from 0 to 1023, analogWrite values from 0 to 255
12}

Notes and Warnings

The PWM outputs generated on pins 5 and 6 may have higher-than-expected duty cycles. This is because of interactions with the

millis()

delay()

See also

• analogWriteResolution()
• PWM
• Blink