Processing

Processing.org

Processing is a framework that considerably simplifies Java development, and provides amazing graphical features.

See how to install it on the Raspberry Pi here.

It seems to be compatible with the projects of this repository.

For example, here is the code that graphically displays the value returned by an ADC (MCP3008):

import analogdigitalconverter.mcp3008.MCPReader;
/*
 * Using Sketch > Add File..., select ADC/build/libs/ADC-1.0-all.jar
 */
int value;
int ADC_CHANNEL = MCP3008Reader.MCP3008_input_channels.CH0.ch(); // Between 0 and 7, 8 channels on the MCP3008

void setup() {
  size(200, 200);
  stroke(255);
  noFill();
  textSize(72);
  MCP3008Reader.initMCP3008();
}
void draw() { // Draw the value of the ADC (MCP3008) at each repaint
  background(0);
  fill(255);
  value = MCP3008Reader.readMCP3008(ADC_CHANNEL);
  text(String.format("%04d", value), 10, 100);
}

About 20 lines, only...

To run the Sketch

• From the project root, to produce the required jar files, run

 $> ./gradlew clean shadowJar

Processing 3.0 might not like a JDK more recent than 1.8. Make sure you set your Java alternative correctly. Processing 4.0 seems to support more recent versions of Java (11, 17, etc).

Note about the JDK to use in Processing

In the installation directory, there is a full JDK. For example, my recent version came with JDK 17, and I wanted to use a JDK 11, already installed on my Raspberry Pi. The script processing-java explains how to change the JDK version.

To change the JDK version:

• In the installation directory, like /tmp/processing-4.0.1:
  • mv java java.17
  • ln -s /usr/lib/jvm/java-11-openjdk-armhf ./java

Then JDK 11 will be used at runtime.
To come back to default, unlink the ./java, and name java.17 back to java.

To see - at runtime - what version of the JDK you are using, run a script simple like this:

void setup() {
    println(String.format("Java Version: %s", System.getProperty("java.version")));    
}

Then you'd see the java version in the console.
Or, to see it also in the GUI:

void setup() {
    println(String.format("Java Version: %s", System.getProperty("java.version")));
    
    size(600, 400);
    stroke(255);
    noFill();
    textSize(72);
    
    fill(255);
    text("Java Version:", 10, 75);
    text(String.format(" %s", System.getProperty("java.version")), 10, 150);
}

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$ [sudo] update-alternatives --config java
$ [sudo] update-alternatives --config javac

• Open the sketch MCP3008_Pie.pde in Processing (no need to copy it anywhere else)

  

• If instructed in the comment at the top of the sketch, use the menu Sketch > Add File... to select the appropriate archive, like here:

/*
 * Using Sketch > Add File..., select ADC/build/libs/ADC-1.0-all.jar
 */

• Make sure your wiring is correct.
• Hit the Run button in Processing.
• Turn the button of the potentiometer, and see for yourself.

A note: Processing and Java

As you would notice, the code of a sketch looks like Java code, but it is not exactly Java code...

Actually, the Processing Development Environment (aka PDE) wraps the code with what is missing for Java to be 100% happy.

If you have for example a sketch like that one:

void setup() {
  size(200, 200);
  stroke(255);
  noFill();
  textSize(72);
}

void draw() {
  background(0);
  fill(255);
  int value = (int)Math.floor(1023 * Math.random());  // Simulation
  text(String.format("%04d", value), 10, 100);
}

Then this code will actually be compiled and executed:

package your.sketch;

import processing.core.PApplet;

public class Sketch extends PApplet {
  public void setup() {
    stroke(255);
    noFill();
    textSize(72);
  }

  public void draw() {
    background(0);
    fill(255);
    int value = (int)Math.floor(1023 * Math.random());  // Simulation
    text(String.format("%04d", value), 10, 100);
  }

  public void settings() {  size(200, 200); }
  
  static public void main(String[] passedArgs) {
    String[] appletArgs = new String[] { "your.sketch.Sketch" };
    if (passedArgs != null) {
      PApplet.main(concat(appletArgs, passedArgs));
    } else {
      PApplet.main(appletArgs);
    }
  }

}

This can be easily reproduced, on any sketch. In the Processing IDE, go to File > Export Application, and see for yourself!

Note: Using a class like above allows you to use the features of Processing, along with the Java 8 syntax and goodies (not supported by the Processing IDE). See about this the code in the src folder, processing.sample.FullSketch.java. The libs folder mentioned in the build.gradle contains archives generated by a File > Export Application.

PitchRoll.pde

Displays the pitch and roll, returned by an LSM303 (accelerometer) sensor.

SSD1306 (oled display)

Mirror - synchronously - the display of the SSD1306.

The RST pin is not necessary. And yes, the 3.3 goes to Vin.

MeArm GUI

MeArm is a ~$42 (2017) robotic arm, using four micro servos.

• One to move the arm up and down (located at the LEFT of the arm)
• One to move the arm back and forth (located at the RIGHT of the arm)
• One to move the arm left and right (located at the BOTTOM of the arm)
• One to open and close the claw (located on the CLAW)

In this example, each servo is driven by a slide bar displayed on the Processing GUI.

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Notes

To know what version of Java Processing is using, just write a sketch like

noLoop();
println(String.format("Using Java version %s", System.getProperty("java.version")));

and run it. The result is shown in the console:

Using Java version 1.8.0_202

Even if you're using Java 8 and above, some limitations seem to exist, regarding lambdas and streaming APIs...
This worked though, on a laptop running Java 11...

import java.util.*;

void setup() {
}

void draw() {
  noLoop();
  println(String.format("Using Java version %s", System.getProperty("java.version")));
  
  println("-------------");
  List list = List.of("Akeu", "Coucou", "Larigou");
  list.forEach(el -> println(el));
  println("-------------");
  list.forEach(System.out::println);
  println("-------------");
}

Console output:

Using Java version 11.0.12
-------------
Akeu
Coucou
Larigou
-------------
Akeu
Coucou
Larigou
-------------

And more to come.

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