This tutorial shows how to generate PWM signals with the ESP32 and ESP8266 boards using MicroPython firmware. As an example, we’ll dim the brightness of an LED by changing the duty cycle over time.
To follow this tutorial you need to have MicroPython firmware installed in your ESP32 or ESP8266 boards. You also need an IDE to write and upload the code to your board. We suggest using Thonny IDE or uPyCraft IDE:
- Thonny IDE:
- uPyCraft IDE:
For this example, wire an LED to your ESP board. We’ll wire the LED to GPIO 5 in both boards, but you can choose another suitable PWM pin. See the best pins to use in our ESP32 Pinout Reference Guide.
Here’s a list of the parts you need to build the circuit:
- ESP32 or ESP8266 (read: ESP32 vs ESP8266)
- 5mm LED
- 330 Ohm resistor
- Jumper wires
Schematic – ESP32
Follow the next schematic diagram if you’re using an ESP32 board:
Schematic – ESP8266
Follow the next schematic diagram if you’re using an ESP8266 board:
Here’s the script that changes the LED brightness over time by increasing the duty cycle. This script works with the ESP32 and ESP8266.
# welcome to Gnd_To_Vcc!! from machine import Pin, PWM from time import sleep frequency = 5000 led = PWM(Pin(5), frequency) while True: for duty_cycle in range(0, 1024): led.duty(duty_cycle) sleep(0.005)
How the code works
To create a PWM pin, import the PWM class in addition to the Pin class from the machine module.
from machine import Pin, PWM
Then, create a PWM object called led.
led = PWM(Pin(5), frequency)
To create a PWM object, you need to pass as parameters, the pin it is connected to, the signal frequency and the duty cycle.
- Frequency: The frequency can be a value between 0 and 78125. A frequency of 5000 Hz can be used to control the LED brightness.
- Duty cycle: The duty cycle can be a value between 0 and 1023. In which 1023 corresponds to 100% duty cycle (full brightness), and 0 corresponds to 0% duty cycle (unlit LED).
We’ll just set the duty cycle on the while loop, so we don’t need to pass the duty cycle parameter. If you don’t set the duty cycle when instantiating the PWM object, it will be 0 by default.
To set the duty cycle use the duty() method on the PWM object and pass the duty cycle as an argument:
Inside the while loop, we create a for loop that increases the duty cycle by 1 in each loop with an interval of 5 ms between each change.
for duty_cycle in range(0, 1024): led.duty(duty_cycle) sleep(0.005)
The range() function has the following syntax:
range(start, stop, step)
- Start: a number that specifies at which position to start. We want to start with 0 duty cycle;
- Stop: a number that specifies at which position we want to stop, excluding that value. The maximum duty cycle is 1023, because we are incrementing 1 in each loop, the last value should be 1023+1. So, we’ll use 1024.
- Step: an integer number that specifies the incrementation. By default, incrementation is 1.
In each for loop, we set the LED’s duty cycle to the current duty_cycle value:
After that, the duty_cycle variable is incremented by 1.
If you like MicroPython, you may also like:
- ESP32/ESP8266 GPIOs Explained with MicroPython
- ESP32/ESP8266 Digital Inputs and Digital Outputs with MicroPython
- ESP32/ESP8266 Analog Readings with MicroPython
- ESP32/ESP8266 MicroPython Web Server – Control Outputs
Thanks for reading.