Processing IDE doesn't read data right from serial

Question

I am trying to make an arduino project with arduino ide and processing ide. I started doing a simple test to see the enviornment where I display the numbers 0,1..9 using arduino ide, but processing ide doesn't read it right for some reason and I can't figure out why, it reads weird numbers from serial like 10, 13, 53 and so on (only these numbers, nothing changes). Here is my processing code:

import processing.serial.*;
Serial port;

void setup() {
  port = new Serial(this,"/dev/ttyUSB0",9600);
}
void draw() {
  if(port.available() > 0) {
  int info = port.read();
  println(info);
  println("===");
  }
}

And here is my arduino code:

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  int deg = 0;
  int data = 1;
  for (deg = 0; deg < 10; deg++) {
    Serial.println(deg);
    delay(15);
    delay(1000);
  }
}

Also, the board and processing are using the same port /dev/ttyUSB0. I am running all of this on Ubuntu 20.04. I tried to look on google but can't seem to find anything. Thanks in advance, any tip is welcome.

Besides bitrate, configure data, parity and stop bits too. The 8-N-1 thing, like https://en.wikipedia.org/wiki/8-N-1 — tevemadar, May 01 '21 at 00:05
I don't think it's that, I followed tutorials and they had no problems, I think there may be an outside problem, not code related, because sometimes if I open processing it says port is busy. — Markus1997, May 01 '21 at 00:26
`Serial.primtln` sends ASCII not binary. Fyi, 10, 13 numeric sequence is an ASCII carriage return/lin feed. The `println` call sends that after it prints the argument. 53 is decimal ASCII for '5'. I think you're reading and printing the ASCII values in your processing IDE code. Try reading the data into a `char` instead of an `int` and print out the `char` values. — lurker, May 01 '21 at 03:37

score 3 · Accepted Answer · answered May 01 '21 at 12:12

Your are sending ASCII from Arduino and reading binary in your Processing IDE. Here is what your sender is doing:

for (deg = 0; deg < 10; deg++) {
  Serial.println(deg);
  ...
}

Serial.println prints the value, meaning it's formatted for display. That means it's converted to ASCII. The output of this will be each number, in ASCII, followed by a new line (thus the 'ln' in the println function):

48 10 13 49 10 13 50 10 13 ... 57 10 13

For example, Serial.println(0) will yield 48 10 13 which is the ASCII code for 0 followed by the new line sequence 10 13 (CR and LF).

Your receiver is doing this:

int info = port.read();
println(info);

Which will read these values as integers and format those numbers as ASCII outputs with new lines. So you will see on your display:

48 
10
13
...

The best way to solve this is to write binary data from Arduino instead of printing the data. On your Arduino, use Serial.write() instead:

for (deg = 0; deg < 10; deg++) {
  Serial.write(deg);
  ...
}

Thanks a lot, I found a workaround by converting the data that I read as a string, by using readStringUntil, now it works just as I wanted, this helped a lot, I thought it was a problem with my setup since I run arduino with sudo becuase if I don't it can't use the port even if I give permissions, thanks. — Markus1997, May 01 '21 at 13:40
@Markus1997 yes, that is another approach I was going to mention. You can process the data as ASCII on the receiver, reading the data as strings instead of numbers. I assumed you cared about the data as binary, so I provided the binary approach. — lurker, May 01 '21 at 13:42

Processing IDE doesn't read data right from serial

1 Answers1