possible open/write two files same time with QFile

[npotency]

I'm using Qextserialport which writes to the serial port as if it was a file (Linux).

Now I also want to generate a log file.

When I have both of these open it seems like I can't write to either of them. Is it even possible to have two files open and write/read from them?

Or do you have to open one and close it, then open the other and close it before using the other.

[drhex]

You can definitely write to several files without having to close other files first. Try making a minimal program that has the problem and if you don't find the bug while making that program, post it here.

[npotency]

Here is some code that works to write to two files. I have a button to send data through the serial port which calls a readADC function. If I manually click this button, it will read the ADC and write to the log file. But as soon as I run a loop to check the ADC automatically, it doesn't get the new value of the ADC. It's the same function. Code is below.

/*********Logging file************************************/
    flog.remove();
    if( !flog.open( QIODevice::ReadWrite | QIODevice::Append ) )
        {
             qDebug("Failed to open file.");
         }
 
 
      log << "Date: ";
      log << QDate::currentDate().toString();
      log << '\n';
      log << "hello world";
       log.flush();         //I had to use flush to get both files to write
      qDebug("File opened.");
     // flog.close();
 
 //This is just a test file to see if I could open two files at once, I could as //long as I used flush.
      //flog.remove();
    if( !fhello.open( QIODevice::ReadWrite | QIODevice::Append ) )
        {
             qDebug("Failed to open file.");
         }
 
 
      hello << "Date: ";
      hello << QDate::currentDate().toString();
      hello << '\n';
      hello << "hello world";
      log.flush();
      qDebug("File opened.");
      fhello.close();
 
/*********************************************************/

/*********Logging file************************************/
    flog.remove();
    if( !flog.open( QIODevice::ReadWrite | QIODevice::Append ) )
        {
             qDebug("Failed to open file.");
         }


      log << "Date: ";
      log << QDate::currentDate().toString();
      log << '\n';
      log << "hello world";
       log.flush();         //I had to use flush to get both files to write
      qDebug("File opened.");
     // flog.close();

 //This is just a test file to see if I could open two files at once, I could as //long as I used flush.
      //flog.remove();
    if( !fhello.open( QIODevice::ReadWrite | QIODevice::Append ) )
        {
             qDebug("Failed to open file.");
         }


      hello << "Date: ";
      hello << QDate::currentDate().toString();
      hello << '\n';
      hello << "hello world";
      log.flush();
      qDebug("File opened.");
      fhello.close();

/*********************************************************/

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int arm_rev0::readADC(int adcnum)
{
    QString adcmsg="ADC ";
   // int randnum;
    adcmsg.append(QString::number(adcnum));
    adcmsg.append(" has been read successfully");
    debug(adcmsg);
    qDebug("Reading ADC");
    //Generate a random ADC reading as a place holder
  //  randnum = rand() % 1024 + 1;
 
    //Get ADC reading from the board
    QByteArray entercmd="", adc="" ,bitsize="";
    entercmd.append(254); //need to append an int, defining it doesn't work, 254 is for command mode
    port->write(entercmd); //enter command mode
    adcnum = adcnum + 149; //shifting to match command set
    adc.append(adcnum); //set adc value to whatever is selected from adcnum
 
    //Clear the serial buffer by storing all the data to a buffer
    char buff[1024];
        int numBytes1;
 
        numBytes1 = port->bytesAvailable();
        if(numBytes1 > 0)
        {
            if(numBytes1 > 1024) numBytes1 = 1024;
 
            int i1 = port->read(buff, numBytes1);
            buff[i1] = '\0';
 
        }
 
      // debug(buff); //Display this for curiousity
      //End clearing serial buffer
 
    port->write(adc); //tell board to return the value of the adc
 
    //Put this byte into a buffer
      char adcbuff[1024];
        int numBytes;
 
        numBytes = 1; //port->bytesAvailable();
        if(numBytes > 0)
        {
            if(numBytes > 1024) numBytes = 1024;
 
            int i = port->read(adcbuff, numBytes);
            adcbuff[i] = '\0';
 
        }
        unsigned char buff1 = adcbuff[0];  //need to convert signed char to unsigned char (otherwise we get signed number eg -1 instead of 255)
        double rawadc = buff1;  //implicitly define buff1 as a double for calculation purposes
        int rawadcint = buff1;
 
    //value of adc is now stored in rawadc
    ui->t_rawadc->setText(QString::number(rawadc)); //display the adc number in raw data box
    debug(QString::number(rawadc));
    //From random number, calculate voltage, and display in voltage box
    double voltrefer, voltage;
    QString currentvolt = ui->voltref->currentText();
    if (currentvolt == "3.3"){
        voltrefer = 3.3;
    }
    else if (currentvolt == "5"){
        voltrefer = 5;
    }
    else if (currentvolt == "8"){
        voltrefer = 8;
    }
    else if (currentvolt == "10"){
        voltrefer = 10;
    }
    else if (currentvolt == "12"){
        voltrefer = 12;
    }
    else if (currentvolt == "15"){
        voltrefer = 15;
    }
    //calculate voltage from number
    voltage = ((rawadc/255 * voltrefer)-0.17) * 25.56;  //This is actually PSI now, need to write a separate equation
    ui->t_voltsadc->setText(QString::number(voltage)); //send to text box
    //end show voltage in voltage box
 
    return(rawadcint); //Returns the raw adc value (0-255)
}

int arm_rev0::readADC(int adcnum)
{
    QString adcmsg="ADC ";
   // int randnum;
    adcmsg.append(QString::number(adcnum));
    adcmsg.append(" has been read successfully");
    debug(adcmsg);
    qDebug("Reading ADC");
    //Generate a random ADC reading as a place holder
  //  randnum = rand() % 1024 + 1;

    //Get ADC reading from the board
    QByteArray entercmd="", adc="" ,bitsize="";
    entercmd.append(254); //need to append an int, defining it doesn't work, 254 is for command mode
    port->write(entercmd); //enter command mode
    adcnum = adcnum + 149; //shifting to match command set
    adc.append(adcnum); //set adc value to whatever is selected from adcnum

    //Clear the serial buffer by storing all the data to a buffer
    char buff[1024];
        int numBytes1;

        numBytes1 = port->bytesAvailable();
        if(numBytes1 > 0)
        {
            if(numBytes1 > 1024) numBytes1 = 1024;

            int i1 = port->read(buff, numBytes1);
            buff[i1] = '\0';

        }

      // debug(buff); //Display this for curiousity
      //End clearing serial buffer

    port->write(adc); //tell board to return the value of the adc

    //Put this byte into a buffer
      char adcbuff[1024];
        int numBytes;

        numBytes = 1; //port->bytesAvailable();
        if(numBytes > 0)
        {
            if(numBytes > 1024) numBytes = 1024;

            int i = port->read(adcbuff, numBytes);
            adcbuff[i] = '\0';

        }
        unsigned char buff1 = adcbuff[0];  //need to convert signed char to unsigned char (otherwise we get signed number eg -1 instead of 255)
        double rawadc = buff1;  //implicitly define buff1 as a double for calculation purposes
        int rawadcint = buff1;

    //value of adc is now stored in rawadc
    ui->t_rawadc->setText(QString::number(rawadc)); //display the adc number in raw data box
    debug(QString::number(rawadc));
    //From random number, calculate voltage, and display in voltage box
    double voltrefer, voltage;
    QString currentvolt = ui->voltref->currentText();
    if (currentvolt == "3.3"){
        voltrefer = 3.3;
    }
    else if (currentvolt == "5"){
        voltrefer = 5;
    }
    else if (currentvolt == "8"){
        voltrefer = 8;
    }
    else if (currentvolt == "10"){
        voltrefer = 10;
    }
    else if (currentvolt == "12"){
        voltrefer = 12;
    }
    else if (currentvolt == "15"){
        voltrefer = 15;
    }
    //calculate voltage from number
    voltage = ((rawadc/255 * voltrefer)-0.17) * 25.56;  //This is actually PSI now, need to write a separate equation
    ui->t_voltsadc->setText(QString::number(voltage)); //send to text box
    //end show voltage in voltage box

    return(rawadcint); //Returns the raw adc value (0-255)
}

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Here's the loop that doesn't work. If I hit a button that calls readADC, it works. But when I call it in this function it doesn't.

while(pressurebad)
    {
        qDebug("Running check main pressure");
        pressurebad = checkMainPressure();
    }

while(pressurebad)
    {
        qDebug("Running check main pressure");
        pressurebad = checkMainPressure();
    }

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int arm_rev0::checkMainPressure() //returns 0 if psi is good, a 1 if not
{
    /*this  checks to see if the main tank is at 100psi, if it isn't it loads or deloads the tank*/
    int pressure;
    pressure = readADC(2); //assume this is hooked to big tank
    /*the adc will return a 255 if the main tank is at 120psi*/
    if ((pressure < (213 + 15)) && (pressure > (213-15)))
    {
        relayoff(3); //turns release valve off of main tank
        relayoff(4); //turns off pumps
        relayoff(5);
        return(0);
    }
    else if (pressure > (213 + 5)) //pressure is too high
    {
        relayon(3); //assumes relay 3 is hooked to release valve of main tank
        relayoff(4);
        relayoff(5);
        qDebug("In greater than");
        return(1);
    }
    else if (pressure < 213 )
    {
        relayon(4); //assumes pumps are hooked to relay 4 and 5
        relayon(5);
        relayoff(3);
        qDebug("In less than");
        return(1);
    }
 
}

int arm_rev0::checkMainPressure() //returns 0 if psi is good, a 1 if not
{
    /*this  checks to see if the main tank is at 100psi, if it isn't it loads or deloads the tank*/
    int pressure;
    pressure = readADC(2); //assume this is hooked to big tank
    /*the adc will return a 255 if the main tank is at 120psi*/
    if ((pressure < (213 + 15)) && (pressure > (213-15)))
    {
        relayoff(3); //turns release valve off of main tank
        relayoff(4); //turns off pumps
        relayoff(5);
        return(0);
    }
    else if (pressure > (213 + 5)) //pressure is too high
    {
        relayon(3); //assumes relay 3 is hooked to release valve of main tank
        relayoff(4);
        relayoff(5);
        qDebug("In greater than");
        return(1);
    }
    else if (pressure < 213 )
    {
        relayon(4); //assumes pumps are hooked to relay 4 and 5
        relayon(5);
        relayoff(3);
        qDebug("In less than");
        return(1);
    }

}

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[npotency]

Here's the debug() function that gets called in readADC. I don't know why it would matter since it worked fine when just clicking a button manually.

void arm_rev0::debug(QString buffer)
{
    /*Write to window
    msg.append(buffer);
    msg.append("\n");
    ui->t_debug->setText(msg);
    */
 
    /*Write to log file*/
 
    log << buffer << '\n';
    log.flush();
 
 
 
}

void arm_rev0::debug(QString buffer)
{
    /*Write to window
    msg.append(buffer);
    msg.append("\n");
    ui->t_debug->setText(msg);
    */

    /*Write to log file*/

    log << buffer << '\n';
    log.flush();



}

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[npotency]

I've narrowed the problem down to this section of code.

void arm_rev0::debug(QString buffer)
{
    /*Write to window
    msg.append(buffer);
    msg.append("\n");
    ui->t_debug->setText(msg);
    */
 
    /*Write to log file*/
 
    log << buffer << '\n';
    log.flush();
 
 
 
}

void arm_rev0::debug(QString buffer)
{
    /*Write to window
    msg.append(buffer);
    msg.append("\n");
    ui->t_debug->setText(msg);
    */
 
    /*Write to log file*/
 
    log << buffer << '\n';
    log.flush();
 
 
 
}

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If I have

/*Write to window
    msg.append(buffer);
    msg.append("\n");
    ui->t_debug->setText(msg);
    */

/*Write to window
    msg.append(buffer);
    msg.append("\n");
    ui->t_debug->setText(msg);
    */

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uncommented, it works. otherwise, it doesn't work. Thoughts?