how to display decimal value to processing from serial input?

in Core Library Questions • 8 months ago

hello guys...
i've got a problem with a processing...
I make some program use processing, which one is temperature sensor program with arduino and DHT11...
i'm finish with arduino and sensor which produce decimal value (float)...
but i can't display that value on processing, processing only display an interger value...

please I wish there's somebody can help me with this problem...

example:
if serial write value 32.90
on processing only display 32.00

the code I use:
float tempC, tempF;

void draw
text(nfc(tempC, 1), 220+xx, 60);
text(nfc(tempF, 1), 220+xx, 100);

thx before for respons... :)

Replies(7)

PhiLho

Re: how to display decimal value to processing from serial input?

8 months ago

What is interesting (and relevant) is how you transmit the value: how it is sent, how it is read...

xanderhan..

Re: how to display decimal value to processing from serial input?

8 months ago

thx Phil..

the value transmit from sensor to arduino with digital input pin....
sent to pc and read on processing use serial cable with float value...
but on processing only display integer value, decimal value was disapear can not display on processing...

can you help me with this problem?

benja

Re: how to display decimal value to processing from serial input?

8 months ago

I think what PhiLho means, is the arduino- and processing-code, wich is used to send and recieve the data. Without the code we can only guess what went wrong.

Maybe this thread helps, it was a question about sending float-values from arduino too:
https://forum.processing.org/topic/sending-data-from-arduino-to-processing-serially#25080000001734449

xanderhan..

Re: how to display decimal value to processing from serial input?

8 months ago

thx benja...

this is the code from arduino and processing:

arduino:

#include "DHT.h"
#define DHTPIN 2
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

int tempPin = 0;
int i;
float samplest[10];
float samplesh[10];

void setup() {
Serial.begin(9600);
dht.begin();
}
void loop() {
float h = dht.readHumidity();
float t = dht.readTemperature();

    Serial.write(h);
    Serial.write(t);
    delay(1000);
}

processing:

import processing.serial.*;

Serial commPort;
PImage bg;
float tempC = 0;
float tempF = 0;
float RH;
float y, h, msbyte, lsbyte;
int yDist, xx=-15;
PFont font12;
PFont font24;

void setup()
{
bg = loadImage("SUHU.jpg");
font12 = loadFont("Garuda-12.vlw");
font24 = loadFont("Garuda-24.vlw");

size(800, 600);

commPort = new Serial(this, "/dev/ttyUSB0", 9600);

}

void draw()
{
while (commPort.available() > 0)
{
    msbyte = commPort.read();
    lsbyte = commPort.read();

    background(bg);

fill(200, 6, 0);
smooth();
stroke(0);
strokeWeight(2);
ellipse(350, 350, 58, 50);
noStroke();
fill(0, 46, 200);
arc(350, 130, 30, 20, PI, PI+PI);
rect(335.2,130,30,200);
// Capillary
fill(250,250, 250);
//stroke(0);
rect(345.2,130,10,200);

// Marks on thermometer
stroke(255, 240, 220);
strokeWeight(1);
textAlign(RIGHT);
fill(0,46,250);
for (int i = 0; i < 5; i += 1) {
line(322, 290-40*i, 332, 290-40*i);
if(i < 4) line(325, 270-40*i, 330, 270-40*i);
textFont(font12);
text(str(40+20*i), 318, 295-40*i);
}

// Centigrade
textAlign(LEFT);
for (int i = 0; i < 6; i += 1) {
line(368, 304-35*i, 378, 304-35*i);
if(i < 5) line(368, 287-35*i, 373, 287-35*i);
textFont(font12);
text(str(0+10*i), 382, 310-35*i);
}

noStroke();
// text font
fill(0,46,250);

    tempC = lsbyte;
    delay(1000);
    RH = msbyte;
    fill(0,0,0);
    textFont(font24);
    textAlign(LEFT);
    tempF = (((tempC)*9)/5) + 32;
    text(nfc(tempC, 1), 165, 190);
    text(nfc(tempF, 1), 165, 250);
    text(nfc(RH, 0), 170, 450);
     fill(200,0, 0);
y = -2.0*tempF + 380;
h = 340-y;
rect(345.2, y, 10, h);
}
}

this is the result for processing:

celcius temperature (tempC) always show zero decimal value...
in fact the arduino sent floating value, example: 31.90, 31.60, 31.20, etc...

I tried to change data type to double, byte, but still does'nt work...

now can anybody correct my code??

thx before for the respons :)

benja

Re: how to display decimal value to processing from serial input?

8 months ago

That arduino-code really works? I mean, are you seeing values with digits when you open the serial-monitor?
Usually you should use "Serial.print()" instead of "Serial.write()", when sending float-values.

I prefer to send one line with values from arduino, seperated by spaces:

Serial.print(h);
Serial.print(" ");
Serial.println(t);

Then in processing using the serialEvent-function to recieve and parse the data:

void serialEvent(Serial p) {
// get message till line break (ASCII > 13)
String message = p.readStringUntil(13);
if (message != null) {
    // try catch function because of possible garbage in received data
    try {
      String[] elements = splitTokens(message);
      RH = float(elements[0]);
      tempC = float(elements[1]);
      println("tempC: "+tempC);
      println("RH: "+RH);
    }
    catch (Exception e) {
    }
}
}

You should remove the while-loop from your sketch then.
And delete the "delay(1000);" from draw(), it should not be needed.

xanderhan..

Re: how to display decimal value to processing from serial input?

8 months ago

thx benja...

yes arduino on serial monitor only show random symbol cause arduino sent a byte data not string....
if I change serial.write to serial.print the processing show a blank window....
cannot read incoming data...

I try to make a simple program using your method still does'nt resolve the problem....
value does'nt appear, only show blank window...

but after I change print to write again, it show the result with no decimal....

benja

Re: how to display decimal value to processing from serial input?

8 months ago

But you have to send strings when you want to transmit float-values. I posted an example in the thread, that i linked to above.
To debug, you can
1. Look into arduinos serial-monitor. Are there float values send?
2. Use "println()" in your processing code, to get information on what parts of code are executed and to see how variable-values change.

If it doesn't work, please Please show what you changed, there must be some mistake.

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