Rotary Encoder

What it is

A knob with no end stops. Inside it, two contacts close and open a quarter of a cycle apart as the shaft turns; each pulls its line, CLOCK or DATA, LOW while it is closed, and a 10 kΩ pull-up holds it HIGH while it is open. The direction is in which of the two falls first, and the distance is how many times they do. Push the knob in and a third switch pulls BTN HIGH.

Unlike a potentiometer, it reports change, not position, so it suits a menu, a volume that should not jump when the program starts, or any value with more range than one turn. The catch is in the reading. A sketch that polls the pins from a loop() with a delay() in it counts perfectly when turned gently and loses count, or counts backwards, when someone flicks it. The handbook below shows why and fixes it with an interrupt.

Each rotation line also has a 100 nF capacitor to GND, which with the pull-up makes a 1 ms filter against contact bounce. It helps; it does not make bounce impossible.

VCC is the level of all three signals

Never 5V beside a 3.3 V board. With VCC unconnected, CLOCK and DATA float and the count wanders on its own.

Which pin is which

Knob side up, header at the bottom, reading left to right:

The back prints TK06 ROTARY ENCODER and ROTATES TO PICK SETTINGS instead of pin names. Turned over, the square pad is on the right, and it is still GND.

Wiring, in five lines

1. GND to your board's GND.
2. VCC to 5V on an Uno, 3V3 on an ESP32, ESP32-S3 or Pico.
3. CLOCK to D2 on an Uno, GPIO 25 on an ESP32, GPIO 4 on an ESP32-S3, GP13 on a Pico.
4. DATA to D3 on an Uno, GPIO 26 on an ESP32, GPIO 5 on an ESP32-S3, GP14 on a Pico.
5. BTN to D4 on an Uno, GPIO 27 on an ESP32, GPIO 6 on an ESP32-S3, GP15 on a Pico.

Leave NC unconnected. Set all three pins to INPUT: the pull-ups and the pull-down are already on the board.

Example

// CLOCK, DATA and BTN, as GPIO numbers.
// Uno: 2, 3, 4. ESP32: 25, 26, 27. ESP32-S3: 4, 5, 6. Pico: 13, 14, 15.
const int CLOCK_PIN = 4;
const int DATA_PIN = 5;

long count = 0;
int lastClock = HIGH;

void setup() {
  Serial.begin(115200);
  pinMode(CLOCK_PIN, INPUT);    // the block has its own pull-ups
  pinMode(DATA_PIN, INPUT);
}

void loop() {
  int clockLevel = digitalRead(CLOCK_PIN);
  if (clockLevel != lastClock) {
    if (clockLevel == LOW) {    // CLOCK has just fallen
      if (digitalRead(DATA_PIN) == HIGH) count++;   // CLOCK first
      else count--;                                 // DATA first
      Serial.println(count);
    }
    lastClock = clockLevel;
  }
}

from machine import Pin

# CLOCK and DATA. ESP32: 25, 26. ESP32-S3: 4, 5. Pico: 13, 14.
clock = Pin(4, Pin.IN)        # no pull: the block has its own
data = Pin(5, Pin.IN)
count = 0
last_clock = 1

while True:
    level = clock.value()
    if level != last_clock:
        if level == 0:        # CLOCK has just fallen
            count += 1 if data.value() == 1 else -1
            print(count)
        last_clock = level

If it counts down when you turn clockwise, swap count++ and count--.

Where to start

The handbook below is ten short articles, each with a working figure. The first count is the whole build in five wires and a few lines.

If the count goes wrong when you turn the knob quickly, read why polling misses steps and then counting with an interrupt.

And before plugging it into an ESP32, VCC sets all three levels is the one page that protects the board.