Qt - Bytearray with empty entries? - c++

Question

I'm working on a simple function which is able to return a int in Qt using information sent to a comport.
I'm using the QSerialPort class which returns a QBytearray.
The problem is i seem (on occasion) to get empty entries in the array that QSerialPort.readAll returns. This makes me unable to convert the bytearray to an int.
The basic functionality is: Ask for Arduino to send either temperature or humidity.
Qt code:
#include <QCoreApplication>
#include <QSerialPortInfo>
#include <QSerialPort>
#include <iostream>
#include <string>
#include <windows.h>
#include <math.h>
using namespace std;
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QString comPort = "COM6";
QSerialPortInfo ArduinoInfo(comPort);
cout << "Manufacturer: " << ArduinoInfo.manufacturer().toStdString() << endl;
cout << "Product Identifier: " << ArduinoInfo.productIdentifier() << endl;
cout << "Vendor Identifier: " << ArduinoInfo.vendorIdentifier() << endl;
QSerialPort Arduino(ArduinoInfo);
Arduino.setBaudRate(QSerialPort::Baud9600);
Arduino.open(QSerialPort::ReadWrite);
Sleep(1000);
if(Arduino.isDataTerminalReady())
cout << "Great Sucess" << endl;
char sending = 'H';
cout << sending << endl;
Arduino.write(&sending, 1);
//int maxSize = Arduino.bytesAvailable();
while(!Arduino.waitForReadyRead()){}
Sleep(100);
QByteArray rawDataArry = Arduino.readAll();
cout << "Shit has been read." << endl;
// Form here on its just write functions, used for debug
cout << "rawData:" << endl;
for(int i=0; i < rawDataArry.size(); i++)
cout << "[" << i << "] "<< rawDataArry[i] << endl;
cout << "All data:" << endl;
for(char s:rawDataArry){
cout << s;
}
cout << endl;
cout << "Converted data:" << endl;
bool ok;
int returnVar = rawDataArry.toInt(&ok, 10);
cout << returnVar << endl;
cout << "Convertion Status:" << ok;
Arduino.close();
return a.exec();
}
The Arduino code is super simple.
#include <dht.h>
dht DHT;
#define PIN_7 7
void setup() {
Serial.begin(9600);
}
void loop()
{
String impString;
while(Serial.available() != 1);
impString = Serial.readString();
DHT.read11(PIN_7);
if(impString == "T")
{
int temp = DHT.temperature;
Serial.println(temp);
}
else if(impString == "H")
{
int humid = DHT.humidity;
Serial.println(humid);
}
emptyReceiveBuf();
delay(100);
}
void emptyReceiveBuf()
{
int x;
delay(200); // vent lige 200 ms paa at alt er kommet over
while (0 < Serial.available())
{
x = Serial.read();
}
}
Terminal monitor displays:

Answer 1

Looks like rawDataArry.size() is returning 4, so that means there ARE 4 bytes in the array. However, when you call rawDataArry[i] it returns a char. Not every char value can be represented as an ascii character. Which is why the last 2 bytes appear empty.
Instead you should try to convert each char to a value that shows the decimal/hex representation of the byte instead of the ascii representation.
Alternatively, you could convert those 4 bytes right to an int and be done with it:
//Big Endian
quint32 myValue(0);
for(int i=0; i<4; i++)
myValue = myValue + (quint8(rawDataArry.at(i)) << (3-i)*8);
//myValue should now have your integer value

Answer 2

I ended up using a member of QByteArray to clean up the widespaces in the array!
It looks something like this!
bool ok;
int returnVal;
do
{
Arduino.write(&imputChar, 1); // Arduino input Char
Arduino.waitForReadyRead();
QByteArray rawDataArry(Arduino.readAll()); // Empties buffer into rawDataArry
QByteArray dataArray(rawDataArry.simplified()); // Removes all widespaces!
returnVal = dataArray.toInt(&ok, 10); // Retuns ByteConvertion - &OK is true if convertion has completed - Widespaces will ruin the conversion
qDebug() << "Converted data:";
qDebug() << returnVal;
qDebug() << "Convertion Status:" << ok;
}while(ok != 1);
return(returnVal);