digitalRead(pin, value) Reads a GPIO pin value. Parameters pin - The GPIO pin number. Returns HIGH (1) or LOW (0) Example #include <Arduino.h> // This program reads a pin and outputs // its value at the specified output pin. int inputPin = 17; // GPIO17 int ledPin = 4; // GPIO4 int val = 0; void setup() { pinMode(inputPin, INPUT); pinMode(ledPin, OUTPUT); } void loop() { val = digitalRead(inputPin); digitalWrite(ledPin); }