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Lesson 17: Rotary Encoder Module

In this lesson, you’ll learn how to use the Raspberry Pi Pico W to control a rotary encoder. The rotary encoder is an advanced sensor that translates knob rotation into an output signal, indicating both the amount and direction of rotation. This project offers hands-on experience with digital input devices, enhancing your ability to work with more complex sensors. You’ll configure the rotary encoder using specific GPIO pins, read its output to determine rotation direction and amount, and master using a button to trigger events.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
Raspberry Pi Pico W	BUY
Rotary Encoder Module	-
Breadboard	BUY

Wiring

Code

Note

Open the 17_rotary_encoder_module.py file under the path of universal-maker-sensor-kit-main/pico/Lesson_17_Rotary_Encoder_Module or copy this code into Thonny, then click “Run Current Script” or simply press F5 to run it. For detailed tutorials, please refer to Open and Run Code Directly.
Here you need to use the rotary_irq_rp2.py, please check if it has been uploaded to Pico W, for a detailed tutorial refer to Upload the Libraries to Pico.
Don’t forget to click on the “MicroPython (Raspberry Pi Pico)” interpreter in the bottom right corner.

from rotary_irq_rp2 import RotaryIRQ
import time
from machine import Pin

# Set GPIO 20 as an input pin for reading the button(sw)'s state
button_pin = Pin(20, Pin.IN, Pin.PULL_UP)

# Initialize the rotary encoder with specific GPIO pins and settings
rotary_encoder = RotaryIRQ(
    pin_num_clk=18,
    pin_num_dt=19,
    min_val=0,
    max_val=14,
    reverse=False,
    range_mode=RotaryIRQ.RANGE_WRAP,
)

# Store the initial value of the rotary encoder and button state
last_rotary_value = rotary_encoder.value()
last_button_state = button_pin.value()

# Main loop
while True:
    # Read the current value of the rotary encoder and button state
    current_rotary_value = rotary_encoder.value()
    current_button_state = button_pin.value()

    # Check if the rotary encoder's value has changed
    if last_rotary_value != current_rotary_value:
        last_rotary_value = current_rotary_value
        print("result =", current_rotary_value)

    # Check if the button's state changed from not pressed to pressed
    if last_button_state and not current_button_state:
        print("Button pressed!")

    # Update the previous state of the button for the next loop iteration
    last_button_state = current_button_state

    # Short delay to prevent debouncing issues
    time.sleep_ms(50)

Code Analysis

Importing Libraries

First, the necessary libraries are imported. rotary_irq_rp2 is for the rotary encoder, time for delays, and machine for hardware control.

For more information about the rotary_irq_rp2 library, please visit MikeTeachman/micropython-rotary.
```
from rotary_irq_rp2 import RotaryIRQ
import time
from machine import Pin
```
Setting up the Button Pin

The GPIO pin connected to the SW pin is configured as an input with a pull-up resistor. This ensures a stable HIGH signal when the button is not pressed.
```
button_pin = Pin(20, Pin.IN, Pin.PULL_UP)
```
Initializing the Rotary Encoder

The encoder is set up with specified GPIO pins for CLK and DT. min_val and max_val define the range of values, and range_mode sets how the value behaves at limits (wraps around in this case).
```
rotary_encoder = RotaryIRQ(
    pin_num_clk=18,
    pin_num_dt=19,
    min_val=0,
    max_val=14,
    reverse=False,
    range_mode=RotaryIRQ.RANGE_WRAP,
)
```
Storing Initial Values

The initial values of the rotary encoder and the button are stored to detect changes in their states later.
```
last_rotary_value = rotary_encoder.value()
last_button_state = button_pin.value()
```

Main Loop

The loop continuously checks for changes in the rotary encoder value and button state. If the rotary value changes, it prints the new value. If the button state changes from unpressed to pressed, it prints “Button pressed!”.

while True:
    current_rotary_value = rotary_encoder.value()
    current_button_state = button_pin.value()

    if last_rotary_value != current_rotary_value:
        last_rotary_value = current_rotary_value
        print("result =", current_rotary_value)

    if last_button_state and not current_button_state:
        print("Button pressed!")

    last_button_state = current_button_state
    time.sleep_ms(50)

The time.sleep_ms(50) at the end of the loop is to prevent debouncing issues, which can cause erratic readings.