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Lesson 17: Rotary Encoder Module

In this lesson, you will learn how to connect and program a rotary encoder with a Raspberry Pi. We will provide step-by-step instructions on writing a Python script that monitors the encoder’s position and button state, with outputs displayed in the console.

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 5	BUY
Rotary Encoder Module	-
Breadboard	BUY

Wiring

Code

from gpiozero import RotaryEncoder, Button
from time import sleep

# Initialize the rotary encoder on GPIO pins 17(CLK) and 27(DT) with wrap-around at max_steps of 16
encoder = RotaryEncoder(a=17, b=27, wrap=True, max_steps=16)
# Initialize the rotary encoder's SW pin on GPIO pin 22
button = Button(22)

last_rotary_value = 0  # Variable to store the last value of rotary encoder

try:
    while True:  # Infinite loop to continuously monitor the encoder
        current_rotary_value = encoder.steps  # Read current step count from rotary encoder

        # Check if the rotary encoder value has changed
        if last_rotary_value != current_rotary_value:
            print("Result =", current_rotary_value)  # Print the current value
            last_rotary_value = current_rotary_value  # Update the last value

        # Check if the rotary encoder is pressed
        if button.is_pressed:
            print("Button pressed!")  # Print message on button press
            button.wait_for_release()  # Wait until button is released

        sleep(0.1)  # Short delay to prevent excessive CPU usage

except KeyboardInterrupt:
    print("Program terminated")  # Print message when program is terminated via keyboard interrupt

Code Analysis

Importing Libraries

The script starts with importing the RotaryEncoder and Button classes from gpiozero for interfacing with the rotary encode, respectively, and the sleep function from the time module for adding delays.
```
from gpiozero import RotaryEncoder, Button
from time import sleep
```
Initializing the Rotary Encoder and Button
- This line initializes a RotaryEncoder object from the gpiozero library. The encoder is connected to GPIO pins 17 and 27.
- The wrap=True parameter means the encoder’s value will reset after reaching max_steps (16 in this case), mimicking a circular dial behavior.
- Here, a Button object is created, connected to GPIO pin 22. This object will be used to detect when the rotary encoder is pressed.
```
encoder = RotaryEncoder(a=17, b=27, wrap=True, max_steps=16)
button = Button(22)
```

Implementing the Monitoring Loop

An infinite loop (while True:) is used to continuously monitor the rotary encoder.
The current value of the rotary encoder is read and compared with its last recorded value. If there’s a change, the new value is printed.
The script checks if the rotary encoder is pressed. On detection of a press, it prints a message and waits until the rotary encoder is released.
A sleep(0.1) is included to add a brief delay, preventing excessive CPU usage.

last_rotary_value = 0

try:
    while True:
        current_rotary_value = encoder.steps
        if last_rotary_value != current_rotary_value:
            print("Result =", current_rotary_value)
            last_rotary_value = current_rotary_value

        if button.is_pressed:
            print("Button pressed!")
            button.wait_for_release()

        sleep(0.1)

except KeyboardInterrupt:
    print("Program terminated")