Arduino UNO Q - Rotary Encoder
A rotary encoder detects rotational motion and direction. Unlike a potentiometer, it can rotate continuously without a limit. In this tutorial, you will learn how to connect a rotary encoder to Arduino UNO Q, count rotation steps, detect direction, and check the counter remotely via Telegram.
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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Additionally, some of these links are for products from our own brand, DIYables .
Overview of Rotary Encoder
Pinout
A rotary encoder module typically has 5 pins:
- CLK (Output A): Pulses once per detent click (LOW→HIGH→LOW)
- DT (Output B): Same pulse as CLK but delayed 90°; used to detect direction
- SW: Built-in pushbutton (LOW when pressed, HIGH when released via pull-up)
- VCC (+): 3.3V or 5V
- GND: Ground
Rotary Encoder vs Potentiometer
- A rotary encoder spins continuously in both directions; a potentiometer is limited to ~270°
- A rotary encoder outputs pulses (digital); a potentiometer outputs voltage (analog)
- Use an encoder when you need to track how much something turned; use a potentiometer when you need to know absolute position
How It Works
When the knob turns, CLK and DT pulse alternately. The 90° phase difference between them tells the direction:
- CLK rises from LOW to HIGH:
- DT is LOW → Clockwise rotation → increment counter
- DT is HIGH → Counter-clockwise rotation → decrement counter
- Detect when CLK transitions from LOW to HIGH
- Read DT to determine direction
- Update a counter: +1 for clockwise, -1 for counter-clockwise
How To Program
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
MCU Code — Rotary Encoder (Polling)
The Arduino UNO Q has two processors: the STM32 MCU (handles real-time hardware control) and the Qualcomm MPU (runs Debian Linux). In this section, only the STM32 MCU is programmed — the Linux side stays idle. A later section will show how both processors work together.
This version uses polling to detect CLK transitions. It is simple but may miss counts if loop() runs slowly:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-rotary-encoder
*/
#include <ezButton.h>
#define CLK_PIN 2 // pin connected to CLK of encoder
#define DT_PIN 3 // pin connected to DT of encoder
#define SW_PIN 4 // pin connected to SW of encoder
#define DIRECTION_CW 0
#define DIRECTION_CCW 1
int counter = 0;
int direction = DIRECTION_CW;
int CLK_state;
int prev_CLK_state;
ezButton button(SW_PIN); // create ezButton object for SW pin
void setup() {
pinMode(CLK_PIN, INPUT);
pinMode(DT_PIN, INPUT);
button.setDebounceTime(50);
prev_CLK_state = digitalRead(CLK_PIN);
}
void loop() {
button.loop();
CLK_state = digitalRead(CLK_PIN);
if (CLK_state != prev_CLK_state && CLK_state == HIGH) {
if (digitalRead(DT_PIN) == HIGH) {
counter--;
direction = DIRECTION_CCW;
} else {
counter++;
direction = DIRECTION_CW;
}
// TO DO: use counter and direction here
}
prev_CLK_state = CLK_state;
if (button.isPressed()) {
// TO DO: button pressed action here
}
}
Detailed Instructions
- First time with Arduino UNO Q? Follow the Getting Started with Arduino UNO Q tutorial to get your development environment ready before proceeding.
- Wire the encoder: Connect CLK to pin 2, DT to pin 3, SW to pin 4, VCC to 3.3V, GND to GND.
- Connect: Plug the Arduino UNO Q into your computer with a USB-C cable.
- Open Arduino App Lab: Launch Arduino App Lab and wait until it detects your Arduino UNO Q.
- Create a new App: Click the Create New App button.
- Give the App a name, for example: DIYables_RotaryEncoder
- Click Create to confirm.
- You will see a set of folders and files generated inside your new App.
- Find the sketch/sketch.ino file — this is where you will paste the MCU sketch.
Paste the sketch: Copy the MCU code above and paste it into the sketch file. Keep other files as default.
- Install the library: Click the Add sketch library button (the open book icon with a + sign) in the left sidebar.
- Search for ezButton created by ArduinoGetStarted.com and click the Install button.
Bricks
No bricks added...
Sketch Libraries
No sketch libra...
Files
python
sketch
.gitignore
README.md
app.yaml
sketch.ino
- Search for Arduino_RouterBridge created by Arduino and click the Install button.
Bricks
No bricks added...
Sketch Libraries
No sketch libra...
Files
python
sketch
.gitignore
README.md
app.yaml
sketch.ino
- Upload: Click the Run button in Arduino App Lab to compile and upload to the STM32.
- Rotate the knob clockwise and counter-clockwise. Counter changes are logged via Bridge Monitor in the next section.
- Press the knob button — a button press event fires.
MCU Code — Rotary Encoder (Interrupt-based)
Using a hardware interrupt on the CLK pin ensures no rotation counts are missed, even when loop() is busy:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-rotary-encoder
*/
#include <ezButton.h>
#define CLK_PIN 2 // pin connected to CLK of encoder
#define DT_PIN 3 // pin connected to DT of encoder
#define SW_PIN 4 // pin connected to SW of encoder
#define DIRECTION_CW 0
#define DIRECTION_CCW 1
volatile int counter = 0;
volatile int direction = DIRECTION_CW;
volatile unsigned long last_time = 0;
int prev_counter;
ezButton button(SW_PIN);
void ISR_encoderChange() {
if ((millis() - last_time) < 50)
return;
if (digitalRead(DT_PIN) == HIGH) {
counter--;
direction = DIRECTION_CCW;
} else {
counter++;
direction = DIRECTION_CW;
}
last_time = millis();
}
void setup() {
pinMode(CLK_PIN, INPUT);
pinMode(DT_PIN, INPUT);
button.setDebounceTime(50);
attachInterrupt(digitalPinToInterrupt(CLK_PIN), ISR_encoderChange, RISING);
}
void loop() {
button.loop();
if (prev_counter != counter) {
// TO DO: use counter and direction here
prev_counter = counter;
}
if (button.isPressed()) {
// TO DO: button pressed action here
}
}
Detailed Instructions
- Use the same wiring and App from the previous example.
- Replace the sketch with the interrupt version and click Run.
- Rotate the knob and press the button — results logged via Bridge Monitor.
Linux + MCU Bridge Programming
The Arduino UNO Q has two processors that work together: the MPU (Qualcomm, runs Debian Linux) and the MCU (STM32, runs Zephyr OS with your Arduino sketch). They communicate using RPC via the Arduino_RouterBridge library — never via raw serial ports.
- The rotary encoder is connected to the MCU (STM32) — wired to digital pins with interrupt support. The MCU tracks the counter and direction in real time.
- The MPU cannot read the encoder directly — it must request the counter value from the MCU via Bridge.call(). The MCU responds immediately.
- The MPU has Wi-Fi — because the MPU runs full Debian Linux with Wi-Fi, it can report the encoder counter via Telegram on demand.
- Communication: Bridge.call() on the Linux side invokes Bridge.provide() functions on the MCU side
- ⚠️ Reserved: /dev/ttyHS1 (Linux) and Serial1 (MCU) are used by the Arduino Router — never open them directly
In short: MPU requests counter → MCU reads current count and direction → MCU reports values → MPU logs or forwards it.
MCU sketch — rotary encoder with Bridge and Monitor output:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-rotary-encoder
*/
#include "Arduino_RouterBridge.h"
#include <ezButton.h>
#define CLK_PIN 2
#define DT_PIN 3
#define SW_PIN 4
#define DIRECTION_CW 0
#define DIRECTION_CCW 1
volatile int counter = 0;
volatile int direction = DIRECTION_CW;
volatile unsigned long last_time = 0;
int prev_counter;
ezButton button(SW_PIN);
void get_counter() {
Monitor.print("Counter: ");
Monitor.print(counter);
Monitor.print(", Direction: ");
Monitor.println(direction == DIRECTION_CW ? "Clockwise" : "Counter-clockwise");
}
void reset_counter() {
counter = 0;
Monitor.println("Counter reset to 0");
}
void ISR_encoderChange() {
if ((millis() - last_time) < 50)
return;
if (digitalRead(DT_PIN) == HIGH) {
counter--;
direction = DIRECTION_CCW;
} else {
counter++;
direction = DIRECTION_CW;
}
last_time = millis();
}
void setup() {
pinMode(CLK_PIN, INPUT);
pinMode(DT_PIN, INPUT);
button.setDebounceTime(50);
attachInterrupt(digitalPinToInterrupt(CLK_PIN), ISR_encoderChange, RISING);
Bridge.begin();
Monitor.begin();
Bridge.provide("get_counter", get_counter);
Bridge.provide("reset_counter", reset_counter);
Monitor.println("Rotary Encoder Bridge ready");
}
void loop() {
button.loop();
if (prev_counter != counter) {
Monitor.print("DIRECTION: ");
Monitor.print(direction == DIRECTION_CW ? "Clockwise" : "Counter-clockwise");
Monitor.print(" | COUNTER: ");
Monitor.println(counter);
prev_counter = counter;
}
if (button.isPressed()) {
Monitor.println("Button pressed");
}
}
Python script (Arduino App Lab) — poll encoder counter from Linux:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-rotary-encoder
*/
from arduino.app_utils import *
import time
def loop():
while True:
Bridge.call("get_counter")
time.sleep(2)
App.run(user_loop=loop)
- Note: Make sure Bridge.begin() is called in the MCU sketch and the sketch is uploaded before running the Python script on the Linux side.
- ⚠️ Warning: Never directly open /dev/ttyHS1 (on Linux) or use Serial1 (on MCU) in your code — these are reserved by the Arduino Router and accessing them will break the Bridge.
Detailed Instructions
- Upload the MCU sketch: Open Arduino App Lab, create a new App, paste the Bridge MCU sketch above into sketch/sketch.ino, install the ezButton and Arduino_RouterBridge libraries, and click Run.
- Add the Python script: Paste the Python code above into the Python tab of the same App.
- Run the App: Click Run — the Python side polls the encoder counter every 2 seconds.
- Rotate the encoder knob in both directions.
- Check the console: Open the Console tab → MCU Monitor subtab to see counter changes logged in real time.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
Rotary Encoder Bridge ready
DIRECTION: Clockwise | COUNTER: 1
DIRECTION: Clockwise | COUNTER: 2
DIRECTION: Clockwise | COUNTER: 3
DIRECTION: Counter-clockwise | COUNTER: 2
DIRECTION: Counter-clockwise | COUNTER: 1
Button pressed
Telegram Integration
Check the encoder counter remotely from anywhere via Telegram.
If you do not have a Telegram bot yet, see How to Create a Telegram Bot to get your bot token before continuing.
MCU sketch: Keep the same MCU sketch from the previous Bridge section — no changes needed. Make sure it is already uploaded and running on the STM32 before proceeding.
Python script (Arduino App Lab) — Telegram bot for encoder counter:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-rotary-encoder
*/
from arduino.app_utils import *
import requests
import time
BOT_TOKEN = "YOUR_BOT_TOKEN"
API_URL = f"https://api.telegram.org/bot{BOT_TOKEN}"
last_update_id = 0
def send_message(chat_id, text):
requests.post(f"{API_URL}/sendMessage", json={"chat_id": chat_id, "text": text})
def get_updates():
global last_update_id
resp = requests.get(f"{API_URL}/getUpdates", params={"offset": last_update_id + 1, "timeout": 5})
return resp.json().get("result", [])
def loop():
global last_update_id
updates = get_updates()
for update in updates:
last_update_id = update["update_id"]
msg = update.get("message", {})
chat_id = msg.get("chat", {}).get("id")
text = msg.get("text", "").strip()
if text == "/count":
counter = Bridge.call("get_counter")
send_message(chat_id, counter)
elif text == "/reset":
Bridge.call("reset_counter")
send_message(chat_id, "Encoder counter has been reset to 0.")
else:
send_message(chat_id, "Commands:\n/count — read encoder counter value\n/reset — reset counter to 0")
time.sleep(1)
App.run(user_loop=loop)
- Note: Replace YOUR_BOT_TOKEN with the token obtained from @BotFather on Telegram.
- Send /count to check the current encoder counter value.
- Send /reset to reset the counter back to 0.
Detailed Instructions
- Upload the MCU sketch: Use the Bridge MCU sketch from the previous section (upload it first if not already done).
- Paste the Telegram script: Copy the Python code above into the Python tab of your App in Arduino App Lab.
- Set your token: Replace YOUR_BOT_TOKEN in the script with your actual bot token.
- Run the App: Click Run — the bot starts listening for Telegram messages.
- Test it: Rotate the encoder, send /count — the bot replies with the counter value and direction.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 12:00:01] Telegram: /count
[2026-04-29 12:00:01] Counter: 5, Direction: Clockwise
[2026-04-29 12:03:20] Telegram: /reset
[2026-04-29 12:03:20] Encoder counter has been reset to 0.
Telegram
12:45
Welcome to Telegram!
ArduinoBot
10:19
Chatting with Arduino...
BotFather
Yesterday
Your bot has been created.
ArduinoBot
bot
OpenClaw Integration
OpenClaw integration for Arduino UNO Q rotary encoder is coming soon.
- Coming Soon: OpenClaw support for rotary encoder reading on Arduino UNO Q will be covered in a future update.
Application/Project Ideas
- Remote volume control: Map encoder rotation to audio volume levels — check current level via Telegram
- Step counter: Count encoder pulses to measure movement in a mechanical system — report via Telegram
- Menu navigator: Use encoder rotation to cycle through options in a remote menu driven from the MPU
- Position tracker: Track absolute position by counting steps from a known home position
- Speed dial: Rotate encoder to set a target speed for a motor — confirm setting via Telegram
Challenge Yourself
- Easy: Add a buzzer that beeps once each time the encoder button is pressed
- Medium: Expose separate callbacks for get_counter(), get_direction(), and get_button_count()
- Advanced: Build a Telegram bot that automatically sends an alert when the counter exceeds a configurable threshold — store the threshold in a Python variable settable via Telegram