how to send float from processing to arduino?

4tex

hello! I'm new to programming, so I'm having problems with understanding how serial works. My goal is to control a robot from Processing via serial to Arduino. Problem appears when I try to send FLOAT to arduino. This is the part of my code that I need help with. How do I send value X ? And I know that this could probably be shorter and better written, but that's not the point here.

thanks for help! :)

float speed;
float x = 200;
color fillE= 255;

    void slider_Servo()
    {
      background(0);
      fill(fillE);
      x = constrain(x, 20, 380);
      smooth();
      ellipse(x,50,25,25);
      if(key == CODED)
      {

        if(keyCode == RIGHT && keyPressed == true)
        {
            x=x+speed;

            fillE= color(0,0,255);
            println(x);
            myPort.write(x);


        }
        else
        {
            x=x;
            fillE=255;
            println(x);
            myPort.write(x);

        }
        if(keyCode == LEFT && keyPressed == true)
        {
          x = x-speed;
          fillE=color(0,0,255);
          println(x);
          myPort.write(x);
        }
        else
        {
          x=x;
          fillE=255;
          println(x);
          myPort.write(x);
        }
        if(keyCode == DOWN)
        {
          if(x > 200)
          {
            x = x-4;
            println(x);
            myPort.write(x);
          }
          if(x < 200)
          {
            x = x+4;
            println(x);
            myPort.write(x);
          }
        }
      }

    }

4tex

oh, and speed value is controled by another slider. just to make things clear.

SilentAce

You need to have a serial connection opened to your arduino and you need to send the value with with write http://arduino.cc/en/Serial/write. And i think that you can't send float to arduino. Here is a processing sketch for rgb led control it might help.

import java.awt.Robot; //java library that lets us take screenshots
import java.awt.AWTException;
import java.awt.event.InputEvent;
import java.awt.image.BufferedImage;
import java.awt.Rectangle;
import java.awt.Dimension;
import processing.serial.*; //library for serial communication

Serial arduino; //creates object "arduino" of serial class
Robot robby; //creates object "robby" of robot class

void setup() {
  println(Serial.list());
  // Usually works with [0], change accordingly
  arduino = new Serial(this, Serial.list()[0], 9600);

  //window size (doesn't matter)
  size(100, 100);

  //standard Robot class error check
  try {
    robby = new Robot();
  } catch (AWTException e) {
    println("Robot class not supported by your system!");
    exit();
  }
}

void draw() {
  //ARGB variable with 32 int bytes where
  int pixel; 
  //sets of 8 bytes are: Alpha, Red, Green, Blue
  float r = 0;
  float g = 0;
  float b = 0;

  int x = displayWidth; //possibly displayWidth
  int y =  displayHeight; //possible displayHeight instead

  //get screenshot into object "screenshot" of class BufferedImage
  BufferedImage screenshot = robby.createScreenCapture(new Rectangle(new Dimension(x,y)));
  //returns the native monitor resolution

  //Skiping every alternate pixel makes the program 4 times faster
  int skipValue = 1;
  int i = 0;
  int j = 0;

  for(i = 0 ; i < x; i = i + skipValue){
    for(j = 0; j < y; j = j + skipValue){
      pixel = screenshot.getRGB(i, j); //the ARGB integer has the colors of pixel (i,j)
      r = r + (int)(255 & (pixel>>16)); //add up reds
      g = g + (int)(255 & (pixel>>8)); //add up greens
      b = b + (int)(255 & (pixel)); //add up blues
    }
  }

  //get the modified resolution for faster performance
  int aX = x/skipValue;
  int aY = y/skipValue;
  r = r / (aX * aY); //average red
  g = g / (aX * aY); //average green
  b = b / (aX * aY); //average blue

  //println(r+","+g+","+b);

  //filter values to increase saturation
  float maxColorInt;
  float minColorInt;

  maxColorInt = max(r, g, b);
  if(maxColorInt == r){
    // red
    if(maxColorInt < (225)){
      r = maxColorInt + 30;  
    }
  } 
  else if (maxColorInt == g){
    //green
    if(maxColorInt < (225)){
      g = maxColorInt + 30;  
    }
  } else {
     //blue
     if(maxColorInt < (225)){
      b = maxColorInt + 30;  
    }  
  }

  //minimise smallest
  minColorInt = min(r, g, b);
  if(minColorInt == r){
    // red
    if(minColorInt > 20){
      r = minColorInt - 20;  
    }
  }
  else if (minColorInt == g){
    //green
    if(minColorInt > 20){
      g = minColorInt - 20;  
    }
  }
  else {
     //blue
     if(minColorInt > 20){
      b = minColorInt - 20;  
    }
  }

  //Send final value to Arduino
  arduino.write(0xff); //write marker (0xff) for synchronization
  arduino.write((byte)(r)); //write red value
  arduino.write((byte)(g)); //write green value
  arduino.write((byte)(b)); //write blue value
  delay(10); //delay for safety

  background(r, g, b); //make window background average color
}

4tex

So how could I send value of slider to arduino? is there even a way?

hondaman900

You can always send the value from Processing as a string and then on the Arduino end ready the bytes and convert the string to a float using

float f = strtof (data);

another variant would be

myFloatVariable = (float)strtod(myStringReadFromSerial);