Digital Input

Digital Input

Review

Analog vs. Digital

  • Analog: infinite variations / states
  • Digital: discrete (or finite) states

Digital

  • Instead of being infinite, digital signals are discrete (or finite)

  • Think binary: the switch is either on or off (not “a little bit on”)

  • Digital values often have more than just two states

    • Still have a fixed number of possible values (e.g. integer values 0-255)

What are examples of digital output?

Digital Output

void setup() {
    pinMode(SOME_PIN, OUTPUT);
}
void loop() { 
    digitalWrite(SOME_PIN, HIGH); //or LOW

  • Most pins on the Photon 2 can be configured to SEND output (e.g. to turn on a light) or to RECEIVE input (e.g. a button press)

  • HIGH / true is 5V (pin VUSB) or 3.3V (pin 3.3v)
  • LOW / false is 0V (ground)

What about digital input?

  • What are examples of digital inputs?

Digital Input

  • Pins D2-D8 can be used for digital input (other pins can also be used)
  • Photon 2 will “read” the voltage on a pin and return HIGH (3.3V) or LOW (0V)
  • Never exceed 3.3V on input
    • Be careful of other components that operate at 5V

Reading Digital Input with digitalRead

Syntax

int value = digitalRead(PIN_NUMBER);
//value is either HIGH or LOW (HIGH and LOW are defined as constants)

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