Recitation 8: Serial Communication by Haiyan Zhang

Part One: Etch A Sketch

For this exercise, use Arduino to send two analog values to Processing via serial communication. To do this, build a circuit with two potentiometers and write an Arduino sketch that reads their values and sends them serially. Then write a Processing sketch that draws an ellipse and reads those two analog values from Arduino. This sketch should modify the ellipse’s x and y values based on the input from Arduino. Just like an Etch A Sketch, one potentiometer should control the ellipse’s x-axis movement, and the other should control the ellipse’s y-axis movement. To see how an Etch A Sketch works, you can watch the video here.

Once you have it working with an ellipse, modify the code to use a line instead (like a real Etch A Sketch).  To do this, you will need to keep track of the previous x and y values so that you can draw a line from there to the new x and y positions.

Arduino Sketch

void setup() {
Serial.begin(9600);
}

void loop() {
int sensorValue1 = analogRead(A0);
int sensorValue2 = analogRead(A1);
int mappedvalue1 = map(sensorValue1, 0, 1023, 0, 600);
int mappedvalue2 = map(sensorValue2, 0, 1023, 0, 600);
Serial.print(mappedvalue1);
Serial.print(“,”);
Serial.print(mappedvalue2);
Serial.println();
delay(1);
}

Processing Sketch

import processing.serial.*;
String myString = null;
Serial myPort;
int x;
int y;
int NUM_OF_VALUES = 2;   
int[] sensorValues;      

void setup(){
 
 size(600,600);
 background(210,237,254);
 setupSerial();
}

void draw(){
  updateSerial();
  
  stroke(random(100),random(100),0);
  strokeWeight(3);
  line(x,y,sensorValues[0],sensorValues[1]);
  x = sensorValues[0];
  y = sensorValues[1];
}

void setupSerial() {
  printArray(Serial.list());
  myPort = new Serial(this, Serial.list()[ 5 ], 9600);
  // WARNING!
  // You will definitely get an error here.
  // Change the PORT_INDEX to 0 and try running it again.
  // And then, check the list of the ports,
  // find the port "/dev/cu.usbmodem----" or "/dev/tty.usbmodem----" 
  // and replace PORT_INDEX above with the index number of the port.

  myPort.clear();
  // Throw out the first reading,
  // in case we started reading in the middle of a string from the sender.
  myString = myPort.readStringUntil( 10 );  // 10 = '\n'  Linefeed in ASCII; 10 means linebreak in ASCII code 
  myString = null;

  sensorValues = new int[NUM_OF_VALUES];
}



void updateSerial() {
  while (myPort.available() > 0) {
    myString = myPort.readStringUntil( 10 ); // 10 = '\n'  Linefeed in ASCII
    if (myString != null) {
      String[] serialInArray = split(trim(myString), ",");
      //put them in the array in this way. remember to put a coma between so that the computer understands 
      if (serialInArray.length == NUM_OF_VALUES) {
        for (int i=0; i<serialInArray.length; i++) {
          sensorValues[i] = int(serialInArray[i]);
        }
      }
    }
  }
}