Issues with serial communication between Arduino and Processing - arduino

Question

I'm attempting to create a data exchange between sensors on an Arduino (well, actually an ATmega328PU-based clone built on a breadboard, but I don't believe that that's the source of my problem) and a Processing script, and I'm getting some unexpected results.
I was following the method of serial communication detailed here, but I get stuck with what appears to be no data actually traveling over the serial connection.
The Arduino code:
int buttonPin = 9, photodiodePin = A0;
char dataToSend;
void setup() {
Serial.begin(9600);
pinMode(buttonPin, OUTPUT);
pinMode(photodiodePin, INPUT);
}
void loop() {
if (Serial.available() > 0)
{
dataToSend = Serial.read();
if (dataToSend == 'B')
{
Serial.println(digitalRead(buttonPin));
}
else if (dataToSend == 'L')
{
Serial.println(analogRead(photodiodePin));
}
}
}
And the relevant parts of the Processing code:
import processing.serial.*;
Serial myPort;
void setup()
{
size(1600, 900);
String portName = Serial.list()[1];
myPort = new Serial(this, portName, 9600);
}
void draw()
{
if(getButtonData() == 1)
{
// Do stuff
}
}
int getLightData()
{
myPort.write('L');
println("L");
while(!(myPort.available() > 0))
{
}
int lightValue = int(myPort.readStringUntil('\n'));
return lightValue;
}
int getButtonData()
{
myPort.write('B');
println("B");
while(!(myPort.available() > 0))
{
println("stuck in here");
delay(500);
}
int buttonValue = int(myPort.readStringUntil('\n'));
return buttonValue;
}
And in Processing I get an output of:
B
stuck in here
stuck in here
stuck in here
stuck in here
...
Note: I know I have the correct port selected from the list, so that is not the issue.
I've tried debugging the issue and searching the Internet for similar problems, both to no avail.

Answer 1

I would first check if simply sending a simple message from Arduino to Processing works. Try something like this in Arduino:
void setup() {
Serial.begin(9600);
}
void loop() {
Serial.println("test");
delay(1000);
}
and this in Processing:
import processing.serial.*;
Serial arduino;
void setup(){
String portName = Serial.list()[1];
try{
arduino = new Serial(this, portName, 9600);
arduino.bufferUntil('\n');
}catch(Exception e){
System.err.println("Error initializing Serial port!\nPlease check connections and port settings");
e.printStackTrace();
}
}
void draw(){
}
void serialEvent(Serial s){
println("received arduino message: " + s.readString());
}
If this simple setup works, you should be fine to move on to the next step and have two way communication. If the above doesn't work then there's something else causing issues with serial communication (in which case please report what errors you're receiving, if any or what behaviour you're experiencing)
In case the above works, you can try two way communication. Notice I'm making use of serialEvent() and bufferUntil. It's best to avoid blocking while loops wherever possible.
Arduino code:
int buttonPin = 9, photodiodePin = A0;
char dataToSend;
void setup() {
Serial.begin(9600);
pinMode(buttonPin, OUTPUT);
pinMode(photodiodePin, INPUT);
}
void loop() {
}
void serialEvent(){
if(Serial.available() > 0){
char cmd = Serial.read();
if(cmd == 'B'){
Serial.println(digitalRead(buttonPin));
}
if(cmd == 'L'){
Serial.println(analogRead(photodiodePin));
}
}
}
Processing code:
import processing.serial.*;
Serial arduino;
int digitalValue;
int analogValue;
int lastCMD;
void setup(){
size(200,100);
String portName = Serial.list()[1];
try{
arduino = new Serial(this, portName, 9600);
arduino.bufferUntil('\n');
}catch(Exception e){
System.err.println("Error initializing Serial port!\nPlease check connections and port settings");
e.printStackTrace();
}
}
void draw(){
background(0);
text("Press 'B' to read digital pin\nPress 'L' to read analog pin\n\n"+
"digital pin: " + digitalValue + "\nanalog pin: " + analogValue,10,25);
}
void keyReleased(){
if(key == 'B' || key == 'L'){
lastCMD = key;
println("sending command" + lastCMD);
if(arduino != null){
arduino.write(lastCMD);
}else println("Arduino is not initializing, not writing to serial port");
}
}
void serialEvent(Serial s){
String rawString = s.readString();
println("received arduino message" + rawString);
try{
rawString = rawString.trim();//remove any white space characters (if present)
if(lastCMD == 'B') digitalValue = int(rawString);
if(lastCMD == 'L') analogValue = int(rawString);
}catch(Exception e){
println("Error parsing String from serial port:");
e.printStackTrace();
}
}