ESP32 - LED - Fade

This tutorial instructs you how to use ESP32 to fade a LED. We also learn how to fade-in/fade-out LED without using delay() function

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×Micro USB Cable
1×LED
1×220 ohm resistor
1×Breadboard
2×Jumper Wires
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Introduction to LED

LED Pinout

LED includes two pins:

  • Cathode(-) pin: connect this pin to GND (0V)
  • Anode(+) pin: is used to control LED's state
  • LED Pinout

How LED Works

After connecting the cathode(-) to GND:

  • If We connect GND to the anode(+), LED is OFF.
  • If We connect VCC to the anode(+), LED is ON.
  • If We generate a PWM signal to the anode(+) pin, the LED's brightness is in proportion to PWM duty cycle. PWM duty cycle varies from 0 to 255. The bigger the PWM duty cycle is, the brighter the LED is.
    • If PWM value is 0, it is equivalent to GND ⇒ LED is OFF
    • If PWM value is 255, it is equivalent to VCC ⇒ LED is ON at the highest brightness.
    • wiring diagram between how led works

※ NOTE THAT:

Usually, it requires a resistor to protect LED from burning. The resistance's value depends on the LED's specification.

ESP32 - fade LED

The ESP32's digital output pins can be programmed to generate PWM signal. By connecting LED's anode(+) pin to an ESP32's pin, LED's cathode(-) to GND, and then programming ESP32 to change the duty cytle of PWM, we We can fade LED.

Wiring Diagram between LED and ESP32

wiring diagram between esp32 led

This image is created using Fritzing. Click to enlarge image

How To Program

  • Configure an ESP32's pin as a digital output pin by using pinMode() function. For example, pin GIOP18:
pinMode(18, OUTPUT);
  • Set brightness of LED by generating PWM signal with corresponding duty cycle by using analogWrite() function:
analogWrite(18, brightness);

Where brightness is a value from 0 to 255.

ESP32 Code - Simple Fade Example

Quick Instructions

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
  • Do the wiring as above image.
  • Connect the ESP32 board to your PC via a micro USB cable
  • Open Arduino IDE on your PC.
  • Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
  • Copy the below code and paste it to Arduino IDE.
/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-led-fade */ #define LED_PIN 18 // ESP32 pin GIOP18 connected to LED int brightness = 0; // how bright the LED is int fadeAmount = 5; // how many points to fade the LED by // the setup routine runs once when you press reset: void setup() { // declare pin GIOP18 to be an output: pinMode(LED_PIN, OUTPUT); } // the loop routine runs over and over again forever: void loop() { // set the brightness of pin GIOP18: analogWrite(LED_PIN, brightness); // change the brightness for next time through the loop: brightness = brightness + fadeAmount; // reverse the direction of the fading at the ends of the fade: if (brightness <= 0 || brightness >= 255) { fadeAmount = -fadeAmount; } // wait for 30 milliseconds to see the dimming effect delay(30); }
  • Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
  • Arduino IDE Upload Code
  • See the brightness of LED

Line-by-line Code Explanation

The above ESP32 code contains line-by-line explanation. Please read the comments in the code!

※ NOTE THAT:

The above example uses the delay() function to fade-in and fade-out. The delay() function makes the LED fade unsmoothly and blocks other code. In the next parts, we will learn how to fade-in and fade-out smoothly without blocking other code by using millis() function

How to fade-in LED in a period without using delay()

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-led-fade */ #define LED_PIN 18 // ESP32 pin GIOP18 connected to LED #define FADE_PEDIOD 3000 // fade time is 3 seconds unsigned long fadeStartTime; // the setup routine runs once when you press reset void setup() { pinMode(LED_PIN, OUTPUT); // declare pin GIOP18 to be an output fadeStartTime = millis(); } // fade-in in loop, and restart after finishing void loop() { unsigned long progress = millis() - fadeStartTime; if (progress <= FADE_PEDIOD) { long brightness = map(progress, 0, FADE_PEDIOD, 0, 255); analogWrite(LED_PIN, brightness); } else { fadeStartTime = millis(); // restart fade again } }

How to fade-out LED in a period without using delay()

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-led-fade */ #define LED_PIN 18 // ESP32 pin GIOP18 connected to LED #define FADE_PEDIOD 3000 // fade time is 3 seconds unsigned long fadeStartTime; // the setup routine runs once when you press reset void setup() { pinMode(LED_PIN, OUTPUT); // declare pin GIOP18 to be an output fadeStartTime = millis(); } // fade-out in loop, and restart after finishing void loop() { unsigned long progress = millis() - fadeStartTime; if (progress <= FADE_PEDIOD) { long brightness = 255 - map(progress, 0, FADE_PEDIOD, 0, 255); analogWrite(LED_PIN, brightness); } else { fadeStartTime = millis(); // restart fade again } }

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