Processing 1.0 - Processing Discourse - How to read float variable from serial port?

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Index › Programming Questions & Help › Electronics, Serial Library › How to read float variable from serial port

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How to read float variable from serial port? (Read 4012 times)

sestys

How to read float variable from serial port?
Oct 2^nd, 2009, 12:22pm

Hi, boys,
I have a problem. I use my Arduino to read a float value and to send it to my Processing. In this code I just send the same value over and over.
Code:

float tempC=23.32;
void setup()
{
Serial.begin(9600); 
}
void loop()
{
Serial.print(tempC);		 
delay(1000);				   
}

I can then see this value in Serial Monitor and in COM Port Toolkit, so it is working, but how can I read it with Processing? I think you can't read a float value from serial port. Could someone include any example of working code? It would really help me, I can't figure it out Cry

NoahBuddy

Re: How to read float variable from serial port?
Reply #1 - Oct 3^rd, 2009, 10:36pm

A couple hints:

-Use println() on the Arduino. This will send an 'end of line' character.

-Parse the serial message as it comes in and watch for that character.

-Use float() to convert a string into a numeric value.

If you still have trouble, I (and I'm sure others) can help. I might have to dig thru my code library to find a working example...

sestys

Re: How to read float variable from serial port?
Reply #2 - Oct 5^th, 2009, 11:50am

Thank you for your response!
I was really confused because I think this should be solved inside processing as it is solved in Wiring - two functions, one for sending(W) and the other(P) for receiving. I will try your hints, but if you find something that seems to be working, post it here. I believe I am not the only one (staring at the Sun Grin

) who is facing this problem.

Btw, I hope, it works good when I send data from Processing to Arduino Undecided

sestys

Re: How to read float variable from serial port?
Reply #3 - Oct 11^th, 2009, 9:33am

Hi, finally I had some time for programming and thanks to NoahBuddy's hints I was successful. If you are facing the same problem I was, my code can help you.

Arduino reads analog input and sends float variable.
Code:

int analogPin = 0;
float temp = 0;

void setup() { 
  Serial.begin(9600);
} 
 
void loop() {
  temp=analogRead(analogPin);
  temp=(map(temp,0,1024,0,5000)/10.0);
  Serial.println(temp); // println add Linefeed to my float
  delay(1000);
}

Processing reads and displays float from serial.
Code:

import processing.serial.*;

int lf = 10;    // Linefeed in ASCII
String myString = null;
Serial myPort;  // Serial port you are using
float num;

void setup() {
  myPort = new Serial(this, Serial.list()[0], 9600);
  myPort.clear();
}

void draw() {
  while (myPort.available() > 0) {
    myString = myPort.readStringUntil(lf);
    if (myString != null) {
	print(myString);  // Prints String
	num=float(myString);  // Converts and prints float
	println(num);
    }
  }
  myPort.clear();
}

huijkman YaBB Newbies Offline Posts: 1	Re: How to read float variable from serial port? Reply #4 - Nov 27^th, 2009, 7:06am Your code indeed helped me. So, thanks a bunch. You just saved me a few hours. Hope I will be able to return the favour somewhere in the future.

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