Read DS18B20 with Raspberry pi

p_seg_rpi

Hi,
i have installed Qt Creator 3.2.1
Based on Qt 5.3.2 (GCC 4.9.2, 32 bit)
Built on May 11 2016 at 17:13:20 in my raspberry pi3

i found header file and c++ code to read the temperature sensor ds18b20.
i have a project file in qt creator where i designed two text labels for (+) and (-)
i use them to increase or decrease the set point for temperature.
i have a third text label3 (Temp) which should display the actual temperature.
i added a LCDnumber module but i don't want to use it to display temperature but i want to keep it for later.

So in my project there are some files like:
-headers ( here i put the header file for ds18b20.h and there is already mainwindow.h)
-source (here i have main.cpp and mainwindow.cpp)
-form (here there is mainwindow.ui)

i tried to put the cpp code to read the sensor in source and i don't know to use the textlabel3
to read the sensor

Here i can't attach my project file.
so here is:
mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "ds18b20.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->connect(this->ui->button_plus, SIGNAL(clicked()), this,SLOT(on_button_plus_click()));
    this->connect(this->ui->button_minus, SIGNAL(clicked()), this,SLOT(on_button_minus_click()));
    this->counter = 19;
    this->ui->label_2->setText(QString::number(counter));
}

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

void MainWindow::on_button_plus_click()
{
        counter++;
        ui->label_2->setText(QString::number(counter));
}

void MainWindow::on_button_minus_click()
{
        counter--;
        ui->label_2->setText(QString::number(counter));
}

//void MainWindow::on_lcd_actual_temp_overflow()
//{

//}

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_button_plus_click();

    void on_button_minus_click();

    void on_lcd_actual_temp_overflow();

    void on_label_temp_linkActivated();

private:
    Ui::MainWindow *ui;
    int counter;
};

#endif // MAINWINDOW_H

ds18b20.h

#ifndef DS18B20_H_
#define DS18B20_H_
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#define CELCIUS 0
#define FAHRENHEIT 1
#define BUS "/sys/bus/w1/devices/"
#define TEMPFILE "/w1_slave"

class DS18B20 {
public:
	DS18B20(const char* address);
	virtual ~DS18B20();
	uint8_t getUnits();
	void setUnits(uint8_t);
	float getTemp();
	float CtoF(float);
private:
	uint8_t unit_;
	char* address_;
	char path[47]; // path should be 46 chars

};

Now i don't know where to put this file:

#include "DS18B20.h"

DS18B20::DS18B20(const char* address) {
	address_ = strdup(address);
	unit_ = CELCIUS;
	snprintf(path, 46, "%s%s%s", BUS, address_, TEMPFILE);
}

DS18B20::~DS18B20() {
}

float DS18B20::getTemp() {
	FILE *devFile = fopen(path, "r");
	if (devFile == NULL) {
		printf("Count not open %s\n", path);
		perror("\n");
	}
	float temp = -1;
	if (devFile != NULL) {
		if (!ferror(devFile)) {
			unsigned int tempInt;
			char crcConf[5];
			fscanf(devFile, "%*x %*x %*x %*x %*x %*x %*x %*x %*x : crc=%*x %s", crcConf);
			if (strncmp(crcConf, "YES", 3) == 0) {
				fscanf(devFile, "%*x %*x %*x %*x %*x %*x %*x %*x %*x t=%5d", &tempInt);
				temp = (float) tempInt / 1000.0;
			}
		}
	}
	fclose(devFile);

	if (unit_ == CELCIUS) {
		return temp;
	} else
		return CtoF(temp);
}

uint8_t DS18B20::getUnits() {
	return unit_;
}

void DS18B20::setUnits(uint8_t u) {
	unit_ = u;
}

float DS18B20::CtoF(float temp) {
	return temp * 1.8 + 32;
}

I can find how to use temp object from cpp code
but where to put this piece of code in my qt project ?
Thank you
for your help

ambershark

@p_seg_rpi You can just put it in your MainWindow class in mainwindow.h as a private variable.

Something like:

class MainWindow : public QMainWindow
{
private:
   DS18B20 *tempReader_;
}

// then you can allocate it in the mainwindow constructor
MainWindow::MainWindow()
{
   tempReader_ = new DS18B20(address);
}

Then to get a temp update just call tempReader_->getTemp(). You could use a QTimer to do this every second (or whatever) and then update your GUI control with the proper temp after every call to getTemp().

Hope that helps.

zeuqma

Hello, i am very new this qt. I tested this example but can not work. Please somebody all of them write source code. How to use configuration ds 18b20