Sending data from arduino to processing, serially.

grimreape..

Sending data from arduino to processing, serially.

in Integration and Hardware • 1 year ago

I have an arduino duemilanove. I'm trying to send an array of positive and negative floating point numbers, stored within the arduino, to processing.
I was going one step at a time by sending a single byte by using the following code and it worked perfectly.

void setup()
{
Serial.begin(9600);
}
byte a=43;
void loop()
{
Serial.write(a);
}

//processing sketch

import processing.serial.*;

Serial myPort;
void setup()
{
String portName = "COM4";

myPort = new Serial(this, portName, 9600);
}
void draw()
{
if(myPort.available()>0)
{
println(myPort.read());
delay(1000);
}
else
{
println("no devices found");
}
}

But, by using "byte" datatype i can send only values between 0-255. How can i modify the above programs so that i can send and receive negative and positive floating point numbers.

Thanks.

Replies(5)

benja

Re: Sending data from arduino to processing, serially.

1 year ago

Hey,

you can store floating-point-values as 'float" in arduino and send them as string with println.

This is an example of how i usually send data from arduino to processing:

arduino:

void setup(){
Serial.begin(9600);
}

void loop(){
float a = -4.56789;
a /= random(10);
Serial.println(a, 5);
delay(500);
}

processing:

import processing.serial.*;
Serial myPort;
float value;

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

void draw()
{
}

void serialEvent(Serial p) {
// get message till line break (ASCII > 13)
String message = myPort.readStringUntil(13);
if(message != null){
value = float(message);
println(value);
}
}

grimreape..

Re: Sending data from arduino to processing, serially.

1 year ago

Thanks a lot. It worked. :D But while trying to use an array of floating point numbers, the processing returns syntax error. I really couldn't find any. Here are the arduino and processing sketches i used.

void setup()
{
Serial.begin(9600);
}
float a[]={-4.31234,1.34524,89.34221,-72.54323};
void loop()
{
for(int i=0;i<4;i++)
Serial.println(a[i],5);
delay(1000);
}

processing sketch

import processing.serial.*;
Serial myPort;
float value;
String message[5];
void setup()
{
String portName="COM4";
myPort = new Serial(this, portName, 9600);
}
void draw()
{
serialEvent();
}
void serialEvent()
{
// get message till line break (ASCII > 13)
for(int i=0;i<4;i++)
{
message[i] = myPort.readStringUntil(13);
if(message[i] != null)
{
value = float(message[i]);
println(value);
}
}
}

Arduino compiles fine, but the processing sketch returns a syntax error at

String message[5] ;

"maybe a missing ] character? ". Any idea what's wrong?

Thanks.

knutl

Re: Sending data from arduino to processing, serially.

1 year ago

String[] message=new String[5];

grimreape..

Re: Sending data from arduino to processing, serially.

1 year ago

Ha. :D Thanks a lot knutl. :D Now it works..

moritz221

Re: Re: Sending data from arduino to processing, serially.

7 months ago

Hey, this code is great, thanks for sharing!

Do you have a code-snipped of how you would read a certain value in the Stringfrom that by any chance? For example the third value it receives '89.34221'? I'm really struggling with that.

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