Serial issues when sending from arduino

lukasz

Serial issues when sending from arduino

in Integration and Hardware • 1 year ago

I had serial working until I tried adding a header. I want to be able to send a header incase I want to send other serial data or upgrade the board--sending header seems like a good practice, however I don't know what I broke. Been at it for few hours.

from what I understand arduino sends data as ASCII string if you use .print() so I use the following to send data from arduino:

int IRpin = 1;
void setup() {
Serial.begin(9600);
}
void loop() {
float volts = analogRead(IRpin)*0.0048828125;
float distance = 65*pow(volts, -1.10);
//map float to an int
int i = (int) distance;
Serial.print("Data,");
Serial.print(i);
Serial.print("\n");
delay(100);
}

easy enough. I can monitor this and it seems to be sending perfectly.

However in processing I then use parseInt to change it from ASCII string to an int so I can check against conditionals (I probably have no idea what I am talking about and this could be totally off, I am very used to JS and using var so string and int mean the same to me):

int posX;
int lastVal = 1000;
int currentVal;
void serialEvent(Serial p) {
String message = myPort.readStringUntil('\n'); // read serial data
if(message != null) {
String [] data = message.split(","); // Split the comma-separated message
println(data);
if ( data[0].equals("Data")){
if( data.length > 1 ){
try {
posX = Integer.parseInt(data[1]);
println("parse worked");
if(posX > 100) {
scrollMe = 0;
println("scroll me is 0");
}
if(posX < 100){
if(posX > lastVal){
scrollMe = scrollMe - 1;
println("scroll me is -1");
}
if(posX < lastVal){
scrollMe = scrollMe + 1;
println("scroll me is 1");
}
}
lastVal = posX;
}
catch (Throwable t) {
print("error"); // parse error
//print(message);
}
}
}
}
println("====");
}

what's stranger still (and super annoying for debugging) is that it seems to only read the serial connection once in a while, that might have to do with the readStringUntil, however I am not sure.

Replies(2)

benja

Re: Serial issues when sending from arduino

1 year ago

Hey,

i think the problem is, that you were using "split()". It splits the message, at the ",", so the second part of the message includes the "\n" at the end of the line, what leads to errors parsing the value.
splitTokens() is more flexible, when you have different delimiters. You could try this:

import processing.serial.*;
Serial port;

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

void serialEvent(Serial p) {
String message = p.readStringUntil('\n'); // read aline of serial data
if (message != null) {
    String [] data = splitTokens(message, ",\n"); // Split the message at ',' or '\n'
    println(data);
    if ( data[0].equals("Data")) {
      if ( data.length > 1 ) {
        int value = int(data[1]);
        println("value recieved: "+value);
      }
    }
}
}

lukasz

Re: Serial issues when sending from arduino

1 year ago

Ah, interesting-- so the readStringUntil('\n') reads it until, but also includes it? My assumption was that it leaves it out. If that is the case I can see now how that would cause problems. It did fix it. thanks much :)

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