Digital Inputs (DI) are one of the four contexts or types of circuits that are core to tangible.
Reference Card:
Download:: Digital Input card [PDF]
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There is a unique card for each context in the tangible matrix and each one indicates the context, command, circuit and offers a code sample.
Context :: Digital Input
If you have not yet looked at the tangible matrix Building Block, you should check it out now. It will introduce you to all four contexts and give a deeper background to the ideas presented here.
Digital refers to signals, circuits, or logical systems that only have two states; ON, OFF.
Input and Output are defined from the perspective of our Arduino. Electrical signals generated in circuits and sent into the Arduino are INPUTS.
So, Digital Inputs are ON/OFF signals (V) that move INTO the Arduino.
Video :: Digital Inputs
Get the Class Slides
Download :: digitalInput-slides-2025
Classic Example
The classic example of a digital input is a button.
Circuit
The classic circuit for testing a digital input is a simple push button (tho any two wires could do). The circuit on left indicates electrical state (state = 0, LOW) when a button is unpressed . The circuit on right indicates electrical state (state = 1,HIGH) when button is pressed.
Command :: digitalRead()
The code that creates a Digital Input is:
state = digitalRead(pin);where:
pin = 2 – 13 (inclusive)
state = 0 OR 1 (gnd or 5V)
Note 1: pin can also include 0,1; but these are reserved for communication, so best to avoid them.
Note 2: pin 13 has the built in LED attached
The line of code above means:
Read the digital (on/off) state of pinX and store that reading in a variable called state.
How Does it Work ?
If the button is pressed, a 5V signal reaches pinX and a 1 ( conceptually a HIGH) is stored in state.
If the button is not pressed (released), a 0V or GND signal reaches pinX and a 0 ( conceptually a LOW) is stored in state.
Important
In Arduino, we read inputs.
Check the Arduino Docs for this topic
Code Sample
int buttonPIN = 12;
int state = 0;
void setup() {
pinMode( buttonPIN, INPUT );
Serial.begin(9600);
}
void loop() {
state = digitalRead( buttonPIN );
Serial.println(state);
}Going Further
Check out analog inputs to see how they compare and contrast with the digital inputs covered here.
Also consider:
And finally – get the overview at: