🔘 Digital Input: Reading Buttons and Switches with ESP32

Digital input lets your ESP32 read button presses, switch states, and other on/off signals. This is how you'll add manual control to your IoT projects - like overriding automated irrigation or starting a pump manually.

🔧 How Digital Input Works

• HIGH (1): Pin reads 3.3V (button not pressed, switch OFF)
• LOW (0): Pin reads 0V (button pressed, switch ON)
• Use pinMode(pin, INPUT_PULLUP) to enable internal pull-up resistor
• Use digitalRead(pin) to read the current state

🔌 Button Wiring

Button Wiring (using internal pull-up):

    ESP32                     Button
    ════                      ══════
    GPIO0 ─────────────────── Button Pin 1
    GND   ─────────────────── Button Pin 2
    
    ⚠️ No external resistor needed - using INPUT_PULLUP!
    
    Button NOT pressed → GPIO reads HIGH (1)
    Button pressed     → GPIO reads LOW (0)
    
    Recommended GPIOs for buttons: GPIO0, GPIO4, GPIO5, GPIO12, GPIO13, GPIO14, GPIO15
    

📖 Basic Button Reading Code

#define BUTTON_PIN 0

void setup() {
    pinMode(BUTTON_PIN, INPUT_PULLUP);
    Serial.begin(115200);
    Serial.println("🔘 Button Reader Ready");
}

void loop() {
    int buttonState = digitalRead(BUTTON_PIN);
    
    if (buttonState == LOW) {
        Serial.println("🔘 Button PRESSED!");
        // Add your action here (e.g., water pump override)
        delay(300);  // Simple debounce
    }
    delay(50);
}
    

🛡️ Button Debouncing (Important!)

Mechanical buttons "bounce" for 5-20ms after press, creating multiple false readings. Here's proper debouncing code:

#define BUTTON_PIN 0

bool lastButtonState = HIGH;
unsigned long lastDebounceTime = 0;
const unsigned long DEBOUNCE_DELAY = 50;
int pressCount = 0;

void setup() {
    pinMode(BUTTON_PIN, INPUT_PULLUP);
    Serial.begin(115200);
    Serial.println("Debounced Button Reader Ready");
}

void loop() {
    bool reading = digitalRead(BUTTON_PIN);
    
    if (reading != lastButtonState) {
        lastDebounceTime = millis();
    }
    
    if ((millis() - lastDebounceTime) > DEBOUNCE_DELAY) {
        if (reading == LOW) {
            pressCount++;
            Serial.printf("✅ Valid button press #%d\n", pressCount);
        }
    }
    lastButtonState = reading;
}
    

🌱 Farm Application: Manual Irrigation Override

#define OVERRIDE_BUTTON 0
#define PUMP_RELAY 5
#define WATER_DURATION 10  // seconds

unsigned long lastPress = 0;
const unsigned long DEBOUNCE = 500;

void setup() {
    pinMode(OVERRIDE_BUTTON, INPUT_PULLUP);
    pinMode(PUMP_RELAY, OUTPUT);
    digitalWrite(PUMP_RELAY, HIGH);  // Pump OFF
    Serial.begin(115200);
    Serial.println("💧 Manual pump override ready");
}

void loop() {
    // Check button press with debounce
    if (digitalRead(OVERRIDE_BUTTON) == LOW) {
        if (millis() - lastPress > DEBOUNCE) {
            Serial.println("🔘 Manual override triggered!");
            digitalWrite(PUMP_RELAY, LOW);   // Pump ON
            delay(WATER_DURATION * 1000);    // Water for X seconds
            digitalWrite(PUMP_RELAY, HIGH);  // Pump OFF
            Serial.println("✅ Watering complete");
            lastPress = millis();
        }
    }
    
    // Your automated irrigation code here...
}
    

🎯 Key Takeaways:

• ✅ Use INPUT_PULLUP for internal resistor (no external parts)
• ✅ Button pressed = LOW (0V), released = HIGH (3.3V)
• ✅ Always debounce (50-100ms delay) to prevent false triggers
• ✅ Use millis() for non-blocking debounce, not delay()
• ✅ Manual override lets operators intervene when needed