Pushbutton Reference

Momentary tactile pushbutton (SPST-NO). The circuit is open when released and closed when pressed.

Pin names

The button has four pins arranged in two pairs. Pins on the same side (1.l/2.l or 1.r/2.r) are always connected to each other internally. Pressing the button bridges the left pair to the right pair.

Pin ID	Label	Description
`1.l`	1 Left	Terminal 1 — left side
`2.l`	2 Left	Terminal 2 — left side (internally connected to `1.l`)
`1.r`	1 Right	Terminal 1 — right side
`2.r`	2 Right	Terminal 2 — right side (internally connected to `1.r`)

For most circuits you only need one pin from each side — use 1.l and 2.l (as in all CNAP templates), or 1.r and 2.r.

Attributes

Name	Description	Default
color	Button cap colour: `"green"`, `"red"`, `"blue"`, `"yellow"`, `"white"`, `"black"`	`"green"`

Wiring

With INPUT_PULLUP (recommended — no external resistor needed)

Connect one pin to an Arduino GPIO, the other to GND. Enable INPUT_PULLUP in setup(). The pin reads HIGH when released, LOW when pressed.

Arduino Pin 2 ── 1.l ┐
                      │ (button)
GND           ── 2.l ┘

const int BTN = 2;

void setup() {
  pinMode(BTN, INPUT_PULLUP);
  Serial.begin(9600);
}

void loop() {
  if (digitalRead(BTN) == LOW) {   // LOW = pressed
    Serial.println("Pressed!");
    delay(200);                     // simple debounce
  }
}

With external pull-down resistor

Connect one pin to 5V, the other to both an Arduino GPIO and a 10 kΩ resistor to GND. The pin reads LOW when released, HIGH when pressed.

5V  ── 1.l ┐
            │ (button)
Pin 2 ── 2.l ── 10kΩ ── GND

Toggle pattern

Press to toggle an LED on/off — detects the falling edge so one press = one toggle:

const int BTN = 2;
const int LED = 13;
bool ledState = false;
bool lastBtn = HIGH;

void setup() {
  pinMode(BTN, INPUT_PULLUP);
  pinMode(LED, OUTPUT);
}

void loop() {
  bool btn = digitalRead(BTN);
  if (btn == LOW && lastBtn == HIGH) {  // falling edge = press
    ledState = !ledState;
    digitalWrite(LED, ledState);
    delay(20);                           // debounce
  }
  lastBtn = btn;
}

Examples

Description	Attrs
Default green cap	`{}`
Red cap	`{ "color": "red" }`
Blue cap	`{ "color": "blue" }`