Digital Outputs (DO) are one of the four contexts or types of circuits that are core to tangible. They are a great tangible starting point as they require simple circuits (just 3 parts) and let us start coding right away.
Reference Card:
Download:: Digital Output card [PDF]
You should print or download a copy of the reference card above and bookmark this page.
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 Output
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 by the Arduino and sent out to circuits are OUTPUTS.
So, Digital Outputs are ON/OFF signals (V) that move OUT of the Arduino.
Video :: Digital Outputs
This first video is from a project that I completed with David Bouchard. An alternate course specific video with an updated circuit can be found below.
VIDEO UPDATE: Digital Outputs
tangible course introduction to digital outputs — this video follows in-class content more closely than the video above. Please note — I extend the first circuit build from class with an RGB LED in this video. If you do not have an RGB LED you can use 2 single color LEDs. You may want to checkout a manual exploration of RGB LEDs using fixed resistors or with code functions if you want more detials on RGB.
Code samples from this video can be found below.
Get the Class Slides
Download :: digitalOutput-slides-2025
Classic Example
The classic example of a digital output is a blinking LED.
Circuit
The classic circuit for testing a digital output is a simple LED and current limiting resistor. Circuit on left when state = 0, LOW, circuit on right when state = 1,HIGH.
Command :: digitalWrite()
The code that creates a Digital Output is:
digitalWrite(pin, state);where:
pin = 2 – 13 (inclusive)
state = LOW (0, Ground) OR HIGH (1, 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:
Write a digital (on/off) signal to pin at level = state (0/LOW or 1/HIGH).
How Does it Work?
If a 1 or HIGH is written, then the voltage (V) at the pin is set to 5V.
If a 0 or LOW is written, then the voltage (V) at the pin is set to 0V (ground).
Important
In Arduino, we Write outputs. Image creating waterfalls on the selected pin.
Check the Arduino Docs for this topic
Code Sample – SINGLE LED
int ledPin = 5 ; // led on pin 5
void setup() {
pinMode ( ledPin , OUTPUT) ; // set direction
}
void loop() {
digitalWrite ( ledPin , 1 ) ; // turn LED on
delay ( 1000 ) ; // wait a bit == 1 second
digitalWrite ( ledPin, 0 ) ; // turn LED off
delay ( 1000 ) ; // wait a bit
}CODE Sample – 2 colors of RGB LED
// code sample using B and R, of RGB led
int blueLED = 5 ; // connect PIN 5 to BLUE pin of RGB LED
int redLED = 10 ; // connect PIN 10 to RED pin of RGB LED
void setup() {
// put your setup code here, to run once:
pinMode ( blueLED , OUTPUT) ;
pinMode ( redLED , OUTPUT) ;
}
void loop() {
// put your main code here, to run repeatedly:
// blue
digitalWrite ( blueLED , HIGH ) ; // turn LED on
delay ( 1000 ) ; // wait a bit == 1 second
digitalWrite ( blueLED, LOW ) ; // turn LED off
delay (1000 ) ; // wait a bit
// red
digitalWrite ( redLED , HIGH ) ;
delay ( 1000 ) ; // wait a bit == 1 second
digitalWrite ( redLED, LOW ) ; // turn LED off
delay (1000 ) ; // wait a bit
}
Going Further
Check out analog outputs to see how they compare and contrast with the digital outputs covered here.
Also consider:
And finally – get the overview at: