ESP32 Pulse-Width Modulation (PWM)

MOHAMMAD SAIFIQUL AIMAN B MOHAMMAD ALI

192011145

R2427-MICROELECTRONIC ENGINEERING

In this part, you'll learn how to dim an LED with the Arduino IDE and the ESP32's LED PWM controller. The ESP32 LED PWM controller has 16 separate channels that may be programmed to do a variety of things. PWM signals with various qualities may be generated. The following are the methods to dim an LED with PWM using the Arduino IDE:

1) First, you need to choose a PWM channel. There are 16 channels from 0 to 15. 

2) Then, you need to set the PWM signal frequency. For an LED, a frequency of 5000 Hz is fine to use.

 3) You also need to set the signal’s duty cycle resolution: you have resolutions from 1 to 16 bits. We’ll use 8-bit resolution, which means you can control the LED brightness using a value from 0 to 255. 

4) Next, you need to specify to which GPIO or GPIOs the signal will appear upon. function accepts two arguments. The first is the GPIO that will output the signal, and second is the channel that will generate the signal.

5) Finally, to control the LED brightness need to use PWM.

Here’s a list of parts you need to assemble the circuit

 ESP32 DOIT DEVKIT V1 Board

 5mm LED 

330 Ohm resistor 

Breadboard 

Jumper wires

ledcAttachPin(GPIO, channel) 

This function accepts two arguments. The first is the GPIO that will output the signal, and the second is the channel that will generate the signal.

ledcWrite(channel, dutycycle)

This function accepts as arguments the channel that is generating the PWM signal, and the duty cycle.

Assemble the circuit shown below

Copy the source code below 

Source code :

// the number of the LED pin

const int ledPin = 16; // 16 corresponds to GPIO16

// setting PWM properties

const int freq = 5000;

const int ledChannel = 0;

const int resolution = 8;

void setup(){

// configure LED PWM functionalitites

ledcSetup(ledChannel, freq, resolution);

// attach the channel to the GPIO to be controlled

ledcAttachPin(ledPin, ledChannel);

}

void loop(){

// increase the LED brightness

for(int dutyCycle = 0; dutyCycle <= 255; dutyCycle++){ 

 // changing the LED brightness with PWM

 ledcWrite(ledChannel, dutyCycle);

 delay(15);

}

// decrease the LED brightness

for(int dutyCycle = 255; dutyCycle >= 0; dutyCycle--){

 // changing the LED brightness with PWM

 ledcWrite(ledChannel, dutyCycle); 

 delay(15);

}

}

Uploading the Sketch :

Before clicking the upload button, go to Tools  Board, and select the board you’re using. In my case. It’s the DOIT ESP32 DEVKIT V1 board. Also don’t forget to select your ESP32’s COM port.

Now, press the upload button.

Then, wait for the “Done uploading.” message: 

Testing your project :

LED will blink dimmer as time goes by.

Getting the Same Signal on Different GPIOs

Different GPIOs can provide the same signal from the same channel. To do this, simply connect those GPIOs to the same setup channel ().

Let's extend the previous example by dimming three LEDs with the same PWM signal coming from the same channel.

Assemble the circuit shown below

Copy the source code below 

Source code :

// the number of the LED pin

const int ledPin = 16; // 16 corresponds to GPIO16

const int ledPin2 = 17; // 17 corresponds to GPIO17

const int ledPin3 = 5; // 5 corresponds to GPIO5

// setting PWM properties

const int freq = 5000;

const int ledChannel = 0;

const int resolution = 8;

void setup(){

// configure LED PWM functionalitites

ledcSetup(ledChannel, freq, resolution);

// attach the channel to the GPIO to be controlled

ledcAttachPin(ledPin, ledChannel);

ledcAttachPin(ledPin2, ledChannel);

ledcAttachPin(ledPin3, ledChannel);

}

void loop(){

// increase the LED brightness

for(int dutyCycle = 0; dutyCycle <= 255; dutyCycle++){ 

 // changing the LED brightness with PWM

 ledcWrite(ledChannel, dutyCycle);

 delay(15);

}

// decrease the LED brightness

for(int dutyCycle = 255; dutyCycle >= 0; dutyCycle--){

 // changing the LED brightness with PWM

 ledcWrite(ledChannel, dutyCycle); 

 delay(15);

}

}

Uploading the Sketch :

Before clicking the upload button, go to Tools  Board, and select the board you’re using. In my case. It’s the DOIT ESP32 DEVKIT V1 board. Also don’t forget to select your ESP32’s COM port.

Now, press the upload button.

Then, wait for the “Done uploading.” message: 

Testing your project :

Three LEDs will blink dimmer as time goes by.