SerialCommunication parsing failing on QT with arduino

Question

I am working on an arduino uno board with an incremental encoder module which I use to detect movement direction and elapsed time between each pulse generated by the encoder which communicates via serial connection and divides two values by comma: a counter int which handles direction and a time int which handles the elapsed time between pulses

#include <SoftwareSerial.h>


unsigned long time;
unsigned long previousTime;
unsigned long elapsedTime;
int contador;
double aceleracion;


int ANTERIORclk;
int VALORclk;
int VALORdt;

//Locación de los pines
int clk=7;
int dt=4;



void setup() {
  pinMode(clk, INPUT);
  pinMode(dt, INPUT);
  ANTERIORclk=digitalRead(clk);
  previousTime= 0;
  contador = 0;

  Serial.begin(9600);
}

void loop() {

  time = millis();
  elapsedTime = time;

  VALORclk=digitalRead(clk);

  //Algoritmo de detección de movimiento
  if(VALORclk!=ANTERIORclk){

    //Si hay movimiento se realizan calculos
    VALORdt=digitalRead(dt);
    elapsedTime -= previousTime;

    if(VALORdt!=VALORclk){
    contador++; 

    }else {
      if (contador>0){
      contador--;
      }
    }

    //Imprimir resultados
    printResults();

    //Se actualizan las lecturas
    ANTERIORclk=VALORclk;  
    previousTime= time;
    delayMicroseconds(.01);
  }//Fin de if y de algoritmo de detección de movimiento
}

  void printResults(){

    Serial.print(contador);
    Serial.print(",\n");
    Serial.print(elapsedTime);
    Serial.print(",\n\n");

  }

Then in qt following one of the QSerialPort tutorials from QT I have a QtWidgets project here: https://github.com/PaulMaxAvalosAguilar/Encoder which as usual it has a MainWindow and for Serial Connection it relies on Connection/SerialConnectionn class which does a connection to readyRead signal in its constructor to the next function:

void SerialConnection::receiveDeviceInfo()
{
    QStringList bufferSplit;

    //serial is of type QSerialPort 
    QByteArray data  = serial->readAll();
    QString parsedDATA;
    double counter = 0;
    double time = 0;

   //serialbuffer is of type QString
    serialbuffer += QString::fromStdString(data.toStdString());
    bufferSplit = serialbuffer.split(",");

    if(!(bufferSplit.length()<3))
    {
        serialbuffer="";

        parsedDATA= bufferSplit.at(0);
        counter = parsedDATA.toDouble();
        parsedDATA= bufferSplit.at(1);
        time = parsedDATA.toDouble();
        qDebug()<<counter<<" -- "<<time<<" "<<bufferSplit.at(2);
    }
}

As you can see the function intends to separate the values by commas so that I can assign it to two variables which later can be displayed on GUI.... The problem, however, is that it all works fine for printing the values but often when I move the encoder a little faster some data is not displayed correctly e.g.:

QApplication: invalid style override passed, ignoring it.
New static SerialConnection Object created
connect() method called
Serial port Opened.... "ttyACM0"
1 -- 342 "\n\n"
2 -- 294 "\n\n"
3 -- 149 ""
4 -- 132 "\n\n"
5 -- 84 "\n\n"
6 -- 78 "\n\n"
7 -- 125 "\n\n"
6 -- 139 "\n\n"
7 -- 1945 "\n\n"
8 -- 89 "\n\n"
9 -- 43 ""
10 -- 32 "\n\n"
11 -- 25 "\n\n"
12 -- 17 "\n"
13 -- 15 "\n\n"
14 -- 990 ""
15 -- 6 "\n\n1"
6 -- 7 "\n\n1"
7 -- 5 "\n\n1"
8 -- 7 "\n\n1"
9 -- 4 "\n\n2"
0 -- 4 "\n\n2"
1 -- 3 "\n\n2"
2 -- 2 "\n\n"
23 -- 2 "\n\n"
24 -- 4 "\n\n"
25 -- 6 "\n\n"
26 -- 7 "\n\n"
27 -- 6 "\n\n"
28 -- 7 "\n\n"
29 -- 4 "\n\n"
30 -- 5 "\n"
31 -- 2 "\n"
30 -- 3 "\n"
31 -- 9 "\n"
30 -- 7 "\n"
31 -- 487 "\n\n"
32 -- 16 "\n\n"
33 -- 13 "\n\n"
34 -- 12 "\n\n3"
5 -- 5 "\n\n3"
4 -- 1 "\n\n3"
5 -- 0 "\n\n3"
6 -- 1 "\n\n"
35 -- 0 "\n\n"
36 -- 1 "\n\n"
37 -- 2 "\n\n"
38 -- 1 "\n\n"
37 -- 0 "\n\n"
38 -- 7 "\n\n"
39 -- 10 "\n"
40 -- 8 ""
41 -- 8 ""
42 -- 456 "\n"
43 -- 7 "\n"
44 -- 4 "\n"
45 -- 4 ""
46 -- 3 ""
47 -- 2 ""
48 -- 2 ""
49 -- 2 ""
50 -- 2 ""
51 -- 2 ""
52 -- 2 ""
53 -- 3 "\n\n5"
4 -- 3 "\n\n5"
5 -- 7 "\n\n5"
6 -- 9 "\n\n5"
7 -- 8 "\n\n5"
8 -- 9 "\n\n5"
9 -- 12 "\n\n"
60 -- 3330 ""
Serial Connection Deleted

You can see how whenever I move the encoder "too fast" some digits are passed to the [2] element in the list then so the next counter is display incorrectly because its last digits moved to the [2] element of the list are missing.

The curious thing is that this never happens when using QT QPlainTextEdit example which no matters how fast I move the encoder always displays everything fine.

Hope anyone can help me

It is Qt, not QT. QT stands for Quick Time.

Innokentiy Alaytsev
– Innokentiy Alaytsev

2017-12-11 09:08:44 +00:00
Commented Dec 11, 2017 at 9:08 — Innokentiy Alaytsev
– Innokentiy Alaytsev, Commented Dec 11, 2017 at 9:08

Vova Shevchyk · Accepted Answer · 2017-12-27 14:16:40Z

1

The issue is in serial port buffer, so that buffer is not released when you call the last function - Serial.print(",\n\n"); - but when it's full, so part of message is released with readyRead() and some numbers are moved to next buffer.

The simplest way to handle this is to print whole message with one function call -

Serial.print(String(QString(contador) + ",\n " + String(elapsedTime) + ",\n\n"));

Or collect your data on readRead to some QByteArray class memeber, so it's available globally in class and latter restructure it. Here is implementation on what I have just described - https://github.com/IndeemaSoftware/IoT-temperature-with-Predix-and-Qt (Handler class in root dir)

Hope you find my answer useful

answered Dec 27, 2017 at 14:16

Vova Shevchyk

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