Published January 29, 2020 © CC BY

From Pixel to NeoPixel

Use the cursor to change the colour of NeoPixels. Create light experiences using visual software like Photoshop or After Effects.

AdvancedFull instructions provided6,716

Things used in this project

Hardware components

Arduino UNO

Any Arduino compatible board would work

Adafruit NeoPixel Digital RGB LED Strip 144 LED, 1m White

Any Neopixel (https://www.adafruit.com/category/168) or WS2812B or SK6812-based LEDs would work

USB-A to B Cable

Breadboard (generic)

Jumper wires (generic)

Hand tools and fabrication machines

Soldering iron (generic)

This is needed when you get Neopixels without wires or pins pre-solderedn on them

Story

This animated image shows how the light of the NeoPixels is influenced by the position of the cursor.

When you want to prototype light behaviour that is beyond the blinking LED, things start to become tricky. You can of course 'hardcode' the behaviour with some for-loops, arrays or a sequence of instructions; but it is a tricky process and is hard when you want to explore; sometimes you don't really know what would look good, or would be understandable.

What if you can just hover over a colour or colours, and you would see how that would look in your prototype or project. Also by moving faster, or slower, you can see how changes and colour transitions would look. Now you can also use more visual-based software, like Photoshop, After Effects, Figma or Sketch.

This project contains two pieces of code; one to capture the current location of the cursor and find out what colour(s) it is pointing to (in Processing). And one that is connected to the Arduino that takes the RGB colours from the screen and sends it to the NeoPixel(s) (of course with a bit of tweaking; servos and other devices could also be controlled in this way).

Especially when you want to sync sound experiences with the light experiences or on-screen animations these examples can help out; in the course sound design at Umeå Institute of design this code has been used to do video prototyping or make experience prototypes (for user-testing or presenting); the sound can be part of an After Effects project while you can also influence the light behaviour (by manipulating visual effects on the screen).

This video shows how you can use the pixels on the screen to create, explore and define light behaviour by NeoPixels. Which is great for prototyping and creating more elegant light than just blinking LEDs.

Movement is more than the shortest way from A to B

Examples of use:

Here is an example of the light guide exploration of Ove by Iris Ritsma, Ivan Kunjasic, Ricardo Verheul and me (Geert Roumen) where it was used to explore the light guide behaviour and see what intensity and colour would work best. In this case, the final experience was hard coded based on the experience that was explored and worked.

A picture showing the After Effect interface on one side and the final prototype for Terra on the other side.

Here is an example of how in the terra project by Manuel Hess, Patrick Krassnitzer & Ferdinand Aichriedler the code was used to sync and control the light and sound experience of the earthquake alarm. In this case, the final experience was with a laptop that was looping through an After Effects video with sound that was audible through external speakers; The Processing sketch was sending it to the prototype which contained NeoPixel LEDs to show the experience.

Steps to make it work

Get the hardware described above (if you don't have NeoPixels you can change the code easily to fade a single LED, RGB LED or something else, but NeoPixels are really shiny so nice for these type of projects).

Get an Arduino, any Arduino will do, as long as it connects to a computer using a serial connection. And download the Arduino (pro) IDE (or use the web editor)

Download the Processing IDE (if you haven't already got it), the code should work both on Mac OSx and Windows, it has been working since 2013 (the AWT robot), so it hopefully continues to work in the future. It might be seen as spyware (in the future); because it literally looks at what happens at your screen, but it doesn't send it anywhere else than to the Arduino.

Download, or copy and paste the code and upload the code to Arduino.

Run the Processing sketch and you should be ready to explore light...

Arduino code explained

The Arduino code is probably the most interesting part to change; so three values are being received from the Processing sketch. r, g and b these can be used in any way to control anything; you could for example use analogWrite(10,r); to write the red value to a pin 10. You could also control the speed of motors, angle of a servo or trigger a solenoid at a specific moment; the sky is the limit. If you prefer blinking LEDs and abrupt motor movements you can also just use digitalWrite(13,r); now the LED connected to pin 13 will be on, except when your hovering over a black; or non-red pixel... Just remember to set pin 13 as an output pinMode(13,OUTPUT);

The protocol is that first an S should be received, after that, it is reading for the bytes of R G and B. It's not exactly watertight this way since the colour value 83 is also perceived as an 'S' by Arduino, but this shouldn't be a big problem...

if(Serial.available()) {   
   if(Serial.read() == 'S') {
     //When it finds an 'S' char, it will wait untill it finds 3 other bytes
     while(!Serial.available()){}
     r = Serial.read();
     while(!Serial.available()){}
     g = Serial.read();
     while(!Serial.available()){}
     b = Serial.read();
   }
   delay(10); // some recovery time, not sure if nessecary
   for(int i=0;i<NUMPIXELS;i++){
   // pixels.Color takes RGB values, from 0,0,0 up to 255,255,255
   pixels.setPixelColor(i, pixels.Color(r,g,b)); // Moderately bright green color.
}

This video shows how a processing sketch is used to send the current pixel of the cursor over to the Arduino which uses it to control the position of the servo. In this way, visual software like After Effects can be used to create and explore more different servo movements.

Processing code explained

In processing it takes a little screenshot of the current pixel at the cursor position; it doesn't see the cursor itself. You can, of course, change that aswell to a fixed position; if you want to be able to still use the cursor.

Processing takes the first Serial port it can find; sometimes this is the right one, sometimes you need to change this to select the right Serial port. This can be done by changing the Serial.list()[0]; to something like Serial.list()[1]; or Serial.list()[2]; in the monitor underneath the Processing sketch you can see the different Serial ports that your operating system can find. In Arduino you can see what the right name of the current port is in the right-bottom of the window.

Code extended

Sometimes you don't want to just send one colour, but you want more of an animation. This is possible by just sending more pixels at the same time. Both sketches need a few adjustments...

A little robot made of two servos waving you goodbye, also made by the After Effects, Processing, Arduino flow.

Bi-directional prototyping

Sometimes you don't want to send values from the screen to the Arduino, but also influence what is happening on the screen using Arduino. I've made several examples that could help you with this.

Using an ESP32 as a keyboard to influence content on your computer or smartphone. Useful for prototyping hybrid interfaces, like consumer products that contain a display.

Using web-serial to communicate back and forth from p5 with the Arduino from a laptop running Google Chrome. Powerful to prototype desktop applications that connect or control hardware.

Using ble-serial to communicate back and forth from p5 with the Arduino from an Android device. Great for prototyping iot apps.

Connecting the micro-bit using ble to p5 from a laptop running Google Chrome. Great for less code heavy users, while still having all the power of the ble.

Code

/*
@Title Processing to Arduino RGB LED (Neopixels)
@Author Geert Roumen
@Institute Umeå Institute of Design
@Date 29-01-2018
 
@Software
IDE:  Processing 3.3.6
OS:   Windows 10.0.17134 Build 17134
*/
 
import java.awt.*;
Robot robot;
import processing.serial.*;
 
Serial myPort;  
int val;       
 
//Setup the communication and Robot instance
//See https://docs.oracle.com/javase/7/docs/api/java/awt/Robot.html#getPixelColor(int,%20int)
 
void setup(){
  size(1000, 150);
  //Connect to the first Serial port of the PC
  String portName = Serial.list()[0];
  print("Serial ports: ");
  println(Serial.list());
  print("Chose ");
  print(portName);
  //Try to open this port
  myPort = new Serial(this, portName, 9600);
  //If you want this window to always stay on top
  //surface.setAlwaysOnTop(true);
 
  //Try to create a AWT Robot
  try
  {
    robot = new Robot();
 
  }catch (AWTException e){
    throw new RuntimeException("Unable to Initialize", e);
  }
 
}
//Make a counter variable
int i=0;
 
void draw(){
  //Get the location of the pointer (mouse/cursor)
  Point mouse;
  mouse = MouseInfo.getPointerInfo().getLocation();
 
  //Get the color at the location of the pointer, pointer icon is ignored
  Color c = robot.getPixelColor(mouse.x,mouse.y);
 
  //Get the integer RGB value at this point
  int top = c.getRGB();
 
  //Write an S to the Serial port
  myPort.write('S'); 
 
  //Do some conversion to make it look white when all colors are 255
  //These values are based on neopixels.
  float r = (float) (red(top)*0.780);//(199/255));
  float g = (float) (green(top)*0.99);//;(254/255));
  float b = (float) (blue(top)*0.56);//(144/255));
 
  //Start writing the [RGB] as three bytes 
  myPort.write((byte) r); 
  myPort.write((byte) g); 
  myPort.write((byte)b);  
  i++;
  stroke(top);
  line(i,0,i+1,150);
}
int j=0;
//if a key is pressed an image of the current 'flow' will be saved.
void keyPressed() {
  j++;
  save("image"+j+".tif");
  background(0);
  i=0;
}

/*
@Title Processing to Arduino RGB LED (Neopixels)
@Author Geert Roumen
@Institute Umeå Institute of Design
@Date 29-01-2018
 
@Hardware
 
Arduino   RGB Neopixel
 
GND       GND
10        Input
5V/USB    Power
 
Arduino
 
https://arduino.cc
 
Neopixel:
https://www.adafruit.com/category/168
 
In this example sketch Processing can send an RGB value to Arduino and Arduino will change the LED color of the NUMPIXELS connected neopixels
*/
 
#include <Adafruit_NeoPixel.h>
 
//
#define PIN            10
 
//The amount of pixels connected to the Arduino, make sure they are powered correctly
#define NUMPIXELS      24
 
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
 
void setup() {
  Serial.begin(9600);
  pixels.begin(); // This initializes the NeoPixel library.
}
 
void loop() {
 
  // For a set of NeoPixels the first NeoPixel is 0, second is 1, all the way up to the count of pixels minus one.
  int r;
  int g;
  int b;
  if(Serial.available()) {   
    if(Serial.read() == 'S') {
      //When it finds an 'S' char, it will wait untill it finds 3 other bytes
      while(!Serial.available()){}
      r = Serial.read();
      while(!Serial.available()){}
      g = Serial.read();
      while(!Serial.available()){}
      b = Serial.read();
    }
    delay(10); // some recovery time, not sure if nessecary
 
    for(int i=0;i<NUMPIXELS;i++){
 
    // pixels.Color takes RGB values, from 0,0,0 up to 255,255,255
    pixels.setPixelColor(i, pixels.Color(r,g,b)); // Moderately bright green color.
 
  }
      pixels.show(); // This sends the updated pixel color to the hardware
  }
 
}

Credits

Geert Roumen

6 projects • 10 followers

I’m a maker and interaction designer, bridging the digital and physical world. and make prototypes and do research in a playful way.