Calling a C function (that return a pointer to struct) every X seconds

ciclonite

Hi all,
I cannot find a simple method for call a c function that read a temperature from a sensor and display the the value using a QLCDNumber.

The c function look like this :

temperature* readCelsius(void) {

    int fd;
    int fault;
    temperature *tmp = (temperature *) malloc(sizeof(*tmp));

    
    char buf[4];
    



    fd = open("/dev/spidev32766.0", O_RDWR);
    if (fd<=0) {
            printf("Device not found\n");
            exit(1);
    }

    if (read(fd, buf, ARRAY_SIZE(buf)) != ARRAY_SIZE(buf))
            perror("SPI read Error");
    close(fd);

    
    fault = buf[1] & FAULT;

   
    if(fault) {
            tmp->scv = buf[3] & SCV;
            tmp->scg = buf[3] & SCG;
            tmp->oc = buf[3] & OC;

            printf("Fault detected: scv: %X, scg: %X, oc: %X\n", tmp->scv, tmp->scg, tmp->oc);
    } else {
            tmp->celsius = ( buf[0] << 4 ) + ( buf[1] >> 2 ) / 4.0;
            printf("Thermocouple temperature: %.2f degrees Celsius\n", tmp->celsius);
    }

    tmp->internal_celsius = ( buf[2] << 2) + ( buf[3] >> 4 )  / 4.0;
    printf("Reference junction temperature: %.2f degrees Celsius\n", tmp->internal_celsius);

    return tmp;


}

From MainWindow i call the function :

temperature *vis = readCelsius();

ui->lcdNumber->display(vis->celsius);
free(vis);

Now i want to call readCelsius() every X seconds and update the value on lcdNumber.
How can i do?
Can i use Qtimer?
Thanks a lot.
Giovanni.

? Offline

Hi! Yes, you can use QTimer for this:

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

// your c function
static int getTempC()
{
    static int temp = 0;
    return ++temp;
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(&m_timer, &QTimer::timeout, this, &MainWindow::updateTemperature);
    m_timer.start(1000);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::updateTemperature()
{
    const auto display = QString("%1").arg(getTempC());
    ui->lcdNumber->display(display);
}