Exercise 1: Make a Processing Etch A Sketch
(1) In the first part of Exercise 1, we were tasked with building 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.
It’s not difficult to do the first part of Exercise 1, the only thing that we need to be careful with is to use the map() function in order to transform the serial value to analog value. And in this case, the map function is not like what it used to be in the class. For the purpose of making the ellipse moving inside the canvas, I think we need to transform the range from 0-1023 to 0-500.
The code for the Arduino part:
// IMA NYU Shanghai
// Interaction Lab
// For sending multiple values from Arduino to Processing
void setup() {
Serial.begin(9600);
}
void loop() {
int sensor1 = analogRead(A0);
int sensor2 = analogRead(A1);
// keep this format
Serial.print(sensor1);
Serial.print(“,”); // put comma between sensor values
Serial.print(sensor2);
Serial.println(); // add linefeed after sending the last sensor value
// too fast communication might cause some latency in Processing
// this delay resolves the issue.
delay(100);
}
The code for the Processing part:
import processing.serial.*;
String myString = null;
Serial myPort;
int NUM_OF_VALUES = 2; /** YOU MUST CHANGE THIS ACCORDING TO YOUR PROJECT **/
int[] sensorValues; /** this array stores values from Arduino **/
void setup() {
size(500, 500);
background(0);
setupSerial();
}
void draw() {
background(0);
updateSerial();
float x = map(sensorValues[0], 0, 1023, 0, width);
float y = map(sensorValues[1], 0, 1023, 0, height);
printArray(sensorValues);
ellipse(x,y,100,100);
// use the values like this!
// sensorValues[0]
// add your code
//
}
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
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), ",");
if (serialInArray.length == NUM_OF_VALUES) {
for (int i=0; i<serialInArray.length; i++) {
sensorValues[i] = int(serialInArray[i]);
}
}
}
}
}
(2) In the second part of Exercise 1, we need to replace the ellipse with a line, making some adjustment on the first part of Exercise 1.
At first, I thought I came up with the solution to the second part which is to add another two variables as the previous x position and the previous y position before the line “updateSerial();” . Yet the line drew by Processing sometimes would disappear, the line is not continuous. Then I found that the problem was that I drew the background in “void draw();”.
The second problem that I met with was that it’s not a continuous line that I drew. It is some identical lines whose positions are constantly changing. Then, I asked a fellow for help, then we found out that I forgot to use the map function for the two new variables.
The code for the Arduino part is the same as that of the first part of Exercise 1.
The code for the Processing:
import processing.serial.*;
String myString = null;
Serial myPort;
int NUM_OF_VALUES = 2; /** YOU MUST CHANGE THIS ACCORDING TO YOUR PROJECT **/
int[] sensorValues; /** this array stores values from Arduino **/
void setup() {
size(500, 500);
background(0);
setupSerial();
}
void draw() {
float pX = map(sensorValues[0], 0, 1023, 0, width);
float pY = map(sensorValues[1], 0, 1023, 0, width);
updateSerial();
float x = map(sensorValues[0], 0, 1023, 0, width);
float y = map(sensorValues[1], 0, 1023, 0, height);
printArray(sensorValues);
stroke(255);
line(pX,pY,x,y);
// use the values like this!
// sensorValues[0]
// add your code
//
}
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
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), ",");
if (serialInArray.length == NUM_OF_VALUES) {
for (int i=0; i<serialInArray.length; i++) {
sensorValues[i] = int(serialInArray[i]);
}
}
}
}
}
Exercise 2: Make a musical instrument with Arduino
The frequency of the tone is controlled by the x position of the mouse, and the tone will be played only when the mouse is pressed
The code for Arduino
[code] #define NUM_OF_VALUES 2 /** YOU MUST CHANGE THIS ACCORDING TO YOUR PROJECT **//** DO NOT REMOVE THESE **/
int tempValue = 0;
int valueIndex = 0;
/* This is the array of values storing the data from Processing. */
int values[NUM_OF_VALUES];
void setup() {
Serial.begin(9600);
pinMode(13, OUTPUT);
pinMode(9, OUTPUT);
}
void loop() {
getSerialData();
// add your code here
// use elements in the values array
// values[0]
// values[1]
if (values[2] == 1) {
tone(9, values[0]);
} else {
noTone(9);
}
}
//recieve serial data from Processing
void getSerialData() {
if (Serial.available()) {
char c = Serial.read();
//switch – case checks the value of the variable in the switch function
//in this case, the char c, then runs one of the cases that fit the value of the variable
//for more information, visit the reference page: https://www.arduino.cc/en/Reference/SwitchCase
switch (c) {
//if the char c from Processing is a number between 0 and 9
case ‘0’…’9′:
//save the value of char c to tempValue
//but simultaneously rearrange the existing values saved in tempValue
//for the digits received through char c to remain coherent
//if this does not make sense and would like to know more, send an email to me!
tempValue = tempValue * 10 + c – ‘0’;
break;
//if the char c from Processing is a comma
//indicating that the following values of char c is for the next element in the values array
case ‘,’:
values[valueIndex] = tempValue;
//reset tempValue value
tempValue = 0;
//increment valuesIndex by 1
valueIndex++;
break;
//if the char c from Processing is character ‘n’
//which signals that it is the end of data
case ‘n’:
//save the tempValue
//this will b the last element in the values array
values[valueIndex] = tempValue;
//reset tempValue and valueIndex values
//to clear out the values array for the next round of readings from Processing
tempValue = 0;
valueIndex = 0;
break;
//if the char c from Processing is character ‘e’
//it is signalling for the Arduino to send Processing the elements saved in the values array
//this case is triggered and processed by the echoSerialData function in the Processing sketch
case ‘e’: // to echo
for (int i = 0; i < NUM_OF_VALUES; i++) {
Serial.print(values[i]);
if (i < NUM_OF_VALUES – 1) {
Serial.print(‘,’);
}
else {
Serial.println();
}
}
break;
}
}
}
[/code]
Code for Processing:
import processing.serial.*;
int NUM_OF_VALUES = 3; /** YOU MUST CHANGE THIS ACCORDING TO YOUR PROJECT **/
Serial myPort;
String myString;
// This is the array of values you might want to send to Arduino.
int values[] = new int[NUM_OF_VALUES];
void setup() {
size(500, 500);
background(0);
printArray(Serial.list());
myPort = new Serial(this, Serial.list()[4 ], 9600);
// check the list of the ports,
// find the port "/dev/cu.usbmodem----" or "/dev/tty.usbmodem----"
// and replace PORT_INDEX above with the index 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
myString = null;
}
void draw() {
background(0);
// changes the values
for (int i=0; i<values.length; i++) {
values[0] = mouseX;
/** Feel free to change this!! **/
}
if(mousePressed) {
values[2]= 1;
} else {
values[2] = 0;
}
// sends the values to Arduino.
sendSerialData();
// This causess the communication to become slow and unstable.
// You might want to comment this out when everything is ready.
// The parameter 200 is the frequency of echoing.
// The higher this number, the slower the program will be
// but the higher this number, the more stable it will be.
echoSerialData(200);
}
void sendSerialData() {
String data = "";
for (int i=0; i<values.length; i++) {
data += values[i];
//if i is less than the index number of the last element in the values array
if (i < values.length-1) {
data += ","; // add splitter character "," between each values element
}
//if it is the last element in the values array
else {
data += "n"; // add the end of data character "n"
}
}
//write to Arduino
myPort.write(data);
}
void echoSerialData(int frequency) {
//write character 'e' at the given frequency
//to request Arduino to send back the values array
if (frameCount % frequency == 0) myPort.write('e');
String incomingBytes = "";
while (myPort.available() > 0) {
//add on all the characters received from the Arduino to the incomingBytes string
incomingBytes += char(myPort.read());
}
//print what Arduino sent back to Processing
print( incomingBytes );
}
