Digital I/O: pinMode, digitalRead, digitalWrite

Digital Pins

Digital pins can be either HIGH (5V) or LOW (0V). Nothing in between.

The Three Functions

pinMode(pin, mode)

Sets a pin as INPUT or OUTPUT. Call this in setup().

pinMode(13, OUTPUT);       // For LEDs, buzzers
pinMode(2, INPUT);          // For buttons, switches
pinMode(2, INPUT_PULLUP);   // Built-in pull-up resistor

digitalWrite(pin, value)

Sets an OUTPUT pin HIGH or LOW.

digitalWrite(13, HIGH);  // 5V, LED on
digitalWrite(13, LOW);   // 0V, LED off

digitalRead(pin)

Reads the state of an INPUT pin. Returns HIGH or LOW.

int state = digitalRead(2);
if (state == HIGH) {
  // Button not pressed (with pull-up)
}

Pin Numbers

| HERO Board | Available Digital Pins | |------------|----------------------| | Digital I/O | 2-13 | | PWM capable (~) | 3, 5, 6, 9, 10, 11 | | LED built-in | 13 | | Avoid | 0, 1 (Serial TX/RX) |

INPUT vs INPUT_PULLUP

• INPUT: Pin floats when nothing connected (reads random values)
• INPUT_PULLUP: Internal resistor pulls pin HIGH when nothing connected

With INPUT_PULLUP:

• Button not pressed → reads HIGH
• Button pressed (connected to GND) → reads LOW