Reading Arduino Serial Data

narner

Hi Everyone! I'm a bit new to Processing and Arduino, so I apologize if this is basic task whose answer I may have missed.

What I'm trying to do is read in a continuous stream of data from a tachometer circuit I made with Arudino, and then feed it into Processing; which I've successfully done using the code below:

if (0 < port.available()) { val = port.read(); println(val); }

What I'm not sure how to do is process the data so that whenever a certain value is detected, an event will occur in Processing.

Thank you! Nick

GoToLoop

Dunno! Perhaps something like this 1? :-/

// forum.processing.org/two/discussion/6894/
// reading-arduino-serial-data

import processing.serial.*;
Serial port;
int val;

static final int CERTAIN_VALUE = 100;

void draw() {
  if (port.available() > 0)  decideWhatToDo(val = port.read());
}

boolean decideWhatToDo(int val) {
  switch (val) {
  case CERTAIN_VALUE : 
    return doCertainThing();
  }

  return false;
}

boolean doCertainThing() {
  return true;
}

narner

Hey there! Thanks for your answer. That's sort of what I ended up trying. I put my code below...perhaps that will help explain what I am trying to do (I should have done that much sooner!)

import processing.video.*; 
import processing.serial.*; 


Serial port; 
Movie myMovie; 
double val = 0; 

void setup() 
{  
 //create screen
 size(320, 240); 
 background(0); 
 //load movie
 myMovie = new Movie(this, "countdown.mov"); 
 myMovie.loop(); 

 // print a list of all available ports 
 println(Serial.list()); 

 // choose the port to which the Arduino is connected 
 // on the PC this is usually COM1, on the Macintosh 
 // this is usually tty.usbserial-XXX 
 port = new Serial(this, "/dev/tty.usbmodem1411", 9600); 
 port.bufferUntil('\n');  
}    


 void draw() { 
 if (0 < port.available()) { 
 String strData = port.readStringUntil('\n'); // string representation of value
 val = Double.parseDouble(strData); // double from string data
}

 image(myMovie, 0, 0); 
}


 void movieEvent(Movie m) {
 m.read();
 if (val == 0) { 
 myMovie.speed(0); 
 } 
 else if (val >= 3600) 
  myMovie.speed(1); 
 else { 
 myMovie.speed(0); 
 } 
}

Basically, I'm using an Arduino Uno to calculate the speed of a computer fan. If the fan stays at 3600 rpm, then I want a movie to play. If it drops below that, I want the movie to stop playing. My Arduino sketch is working (I'm able to read in the data fine on the serial port), but for some reason I can't do that with Processing; no data appears to be coming in. I based this off of other serial read examples I found, but nothing seems to work yet.

theleadingzero

It's difficult to debug without seeing the Arduino side of the code as well.

Two things to check: 1. All other serial monitors and applications reading in from that port are closed (only one application can read from a serial port at a time). 2. Your data from the Arduino actually terminates with a \n, so it should be using Serial.println not Serial.print.

Additionally, have you gotten the other serial examples that you've found working?

narner

Right, how silly....here's the Arduino code I'm using:

//// This example shows one way of creating an optoswitch
//// using an IR LED as emitter and an IR LED receiver as
//// light sensor.
////
////           + GROUND                                 +GROUND          
////           |                                        |  
////           <                                        < 
////           > 220 ohm resistor                       > 220 ohm resistor
////           <                                        <      
////           |                                        |  
////           |                                        |
////         -----                                    -----
////          / \    >>IR LED emitter >>>>>>>>>>>>>>>>  / \   IR LED receiver
////         -----                                    -----
////           |                                        |
////           |                                        |
////           + +5VCD                                  +  ANALOG INPUT 0
////
////
////
////http://playground.arduino.cc/Learning/Tachometer


int val;
long last=0;
int currentStatus=LOW;
int previousStatus=LOW;
int count=0;

int sens=85;  // this value indicates the limit reading between dark and light,
              // it has to be tested as it may change acording on the 
              // distance the leds are placed.
int nSpokes=7; // the number of blades of the wheel

int milliseconds=500; // the time it takes each reading



void setup()  
{
  Serial.begin(9600);
  pinMode(13,OUTPUT);
}

void loop()
{
  val=analogRead(0);
  if(val<sens)
    currentStatus=LOW;
   else
    currentStatus=HIGH;
   digitalWrite(13,currentStatus); //as iR light is invisible for us, the led on pin 13 
                          //indicate the state of the circuit.

   if(previousStatus!=currentStatus){  //counts when the state changes from (dark to light) or 
                     //from (light to dark), remmember that IR light is invisible for us.
     count++;
     previousStatus=currentStatus;
   }
   if(millis()-last>=milliseconds){
     double rps=((double)count/nSpokes)/2.0*1000.0/milliseconds;
     double rpm=((double)count/nSpokes)/2.0*60000.0/(milliseconds);
//     Serial.print((count/2.0));Serial.print("  RPS ");Serial.print(rps);
//     Serial.print(" RPM");
//     Serial.print(rpm);
//     Serial.print("  VAL ");Serial.println(val); 
     Serial.println(rpm);
     count=0;
     last=millis();
   }
}

In regards to your suggestions: 1. Yes, I don't have any other serial applications open. 2. I did try changing my Arduino code from 'Serial.print' to 'Serial.println', but it didn't seem to have any effect.

And yes, I did get the following example to work fine; it reads in data from a potentiometer on pin 0.

/*
  AnalogReadSerial
  Reads an analog input on pin 0, prints the result to the serial monitor.
  Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

 This example code is in the public domain.
 */

// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin 0:
  int sensorValue = analogRead(A2);
  // print out the value you read:
  Serial.println(sensorValue);
  delay(1);        // delay in between reads for stability
}

edit: @theleadingzero, The other serial example that I got to work was the 'SerialEvent' sketch included under File/Examples/Communication.