【飛凌嵌入式 OK3399-C+開發(fā)板試用體驗(yàn)】使用QT工程讀取DHT11模塊的波折經(jīng)歷
作者：donatello1996
上一帖中已經(jīng)成功使用一個(gè)簡(jiǎn)單的main函數(shù)成功讀取到DHT11的溫濕度數(shù)據(jù)了，雖然讀取溫濕度數(shù)據(jù)響應(yīng)時(shí)間很慢，但至少算是成功讀取了，這次我就想在QT環(huán)境下進(jìn)行溫濕度的讀取，結(jié)合美觀的圖形界面呈現(xiàn)出來，同時(shí)，還可以以文件形式讀取ADC_IN4接口 CPU0溫度以及CPU1溫度，使用到的QT類為QThread，還有Linux系統(tǒng)自帶的pthread。為什么說是波折經(jīng)歷呢，因?yàn)镈HT11這個(gè)器件對(duì)主控和系統(tǒng)的實(shí)時(shí)性要求實(shí)在是太高了，如果是直接用單片機(jī)主控來讀取，那就沒任何問題，但是要用到微處理器，哪怕是RK3399這種主頻那么高的CPU，讀取DHT11依然會(huì)出現(xiàn)實(shí)時(shí)性問題，這就很煩，由于QT的圖形化界面用到了QMainWindow類，會(huì)占用一定的CPU實(shí)時(shí)資源，在這一兩天的探索過程中，我先后用了QThread pthread QTimer三種方式讀取DHT11數(shù)據(jù)，結(jié)果表明，要想穩(wěn)定讀取，只能用pthread進(jìn)行，QThread這種QT內(nèi)建的多線程實(shí)現(xiàn)類完全無法讀取，頂多只能讀取已經(jīng)存在/sys中的實(shí)時(shí)CPU溫度數(shù)據(jù)和ADC接口數(shù)據(jù)，而QTimer這種定時(shí)器中斷類就更不用說了，實(shí)時(shí)性比QThread還低得多，跟pthread的效率比起來就沒法比。我不知道QThread的實(shí)現(xiàn)代碼是怎么寫的，按我理解來說應(yīng)該也只是對(duì)pthread做一定的封裝，也沒想到實(shí)時(shí)性/效率差這么遠(yuǎn)。
首先是讀寫兩個(gè)CPUzone的溫度，需要讀取/sys/class/thermal/thermal_zone0/temp和/sys/class/thermal/thermal_zone1/temp：
int fd_cputemp0，fd_cputemp1;
unsigned char buf_cpu_temp0[5];
unsigned char buf_cpu_temp1[5];
fd_cputemp0 = open("/sys/class/thermal/thermal_zone0/temp", O_RDONLY);
fd_cputemp1 = open("/sys/class/thermal/thermal_zone1/temp", O_RDONLY);
read(fd_adc4 , buf_adc4 ,5);
read(fd_cputemp0 , buf_cpu_temp0 ,5);
read(fd_cputemp1 , buf_cpu_temp1 ,5);
而ADC_IN4則是用同樣的方法讀取/sys/bus/iio/devices/iio:device0/in_voltage4_raw：
int fd_adc4;
unsigned char buf_adc4[5];
fd_adc4 = open("/sys/bus/iio/devices/iio:device0/in_voltage4_raw", O_RDONLY);
read(fd_adc4 , buf_adc4 ,5);
#ifndef MY_THREAD_H
#define MY_THREAD_H
#include <QThread>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "mainwindow.h"
class MainWindow;
class mythread : public QThread
{
public:
mythread(QObject *parent);
void closeThread();
struct timeval tv1;
protected:
virtual void run();
private:
volatile bool isStop;
MainWindow *m_pMainWindow;
int fd_cputemp0,fd_cputemp1,fd_adc4;
};
#endif // DHT11_THREAD_H
#include "mythread.h"
#include "mainwindow.h"
#include <ui_mainwindow.h>
mythread::mythread(QObject *parent)
{
isStop = false;
m_pMainWindow = qobject_cast<MainWindow*>(parent);
}
void mythread::closeThread()
{
isStop = true;
}
extern float dht11_temp,dht11_humi;
void mythread::run()
{
int i=0;
unsigned char buf_adc4[5];
unsigned char buf_cpu_temp0[5];
unsigned char buf_cpu_temp1[5];
while (1)
{
if(isStop)
return;
//gettimeofday(&tv1, NULL);
//qDebug("tv1=%d\n",tv1.tv_usec);
fd_adc4 = open("/sys/bus/iio/devices/iio:device0/in_voltage4_raw", O_RDONLY);
fd_cputemp0 = open("/sys/class/thermal/thermal_zone0/temp", O_RDONLY);
fd_cputemp1 = open("/sys/class/thermal/thermal_zone1/temp", O_RDONLY);
read(fd_adc4 , buf_adc4 ,5);
read(fd_cputemp0 , buf_cpu_temp0 ,5);
read(fd_cputemp1 , buf_cpu_temp1 ,5);
buf_adc4[4]=0;
m_pMainWindow->ui->L1->setText(QString("%1").arg(dht11_temp));
m_pMainWindow->ui->L2->setText(QString("%1").arg(dht11_humi));
m_pMainWindow->ui->L3->setText(QString((char*)buf_adc4));
m_pMainWindow->ui->L4->setText(QString((char*)buf_cpu_temp0));
m_pMainWindow->ui->L5->setText(QString((char*)buf_cpu_temp1));
sleep(1);
}
}
struct dht11_data
{
unsigned short temp;
unsigned short hum;
}curdht11_data;
float dht11_temp,dht11_humi;
pthread_t id;
int fd_dht11;
void *Thread_CPU_Temp(void *arg)
{
int retval;
while(1)
{
retval = read ( fd_dht11 , &curdht11_data , sizeof(curdht11_data) );
if ( retval == -1 )
{
printf ( "read dht11 error" ) ;
}
if(curdht11_data.temp != 0xffff)
{
if(0 < (curdht11_data.temp>>8) && (curdht11_data.temp>>8) < 85)
{
dht11_temp = (curdht11_data.temp >> 8) + (curdht11_data.temp & 0xff) * 0.01;
dht11_humi = (curdht11_data.hum >> 8) + (curdht11_data.hum & 0xff) * 0.01;
printf("---- %f %f-----\n",dht11_temp,dht11_humi);
}
}
//sleep(1);
}
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
fd_dht11 = open ( "/dev/dht11" , O_RDONLY) ;
if ( fd_dht11 == -1 )
{
perror ( "open dht11 error\n" ) ;
}
printf ( "open /dev/dht11 successfully\n" ) ;
pthread_create(&id , NULL , Thread_CPU_Temp , NULL);
printf ( "create pthread successfully\n" ) ;
MainWindow w;
w.show();
return a.exec();
}
void MainWindow::on_PB1_clicked()
{
disconnect(ui->PB1,SIGNAL(clicked()),this,SLOT(on_PB1_clicked()));
connect(ui->PB1,SIGNAL(clicked()),this,SLOT(on_PB1_clicked_2()));
ui->PB1->setText("Pause");
thread1->start();
}
void MainWindow::on_PB1_clicked_2()
{
disconnect(ui->PB1,SIGNAL(clicked()),this,SLOT(on_PB1_clicked_2()));
connect(ui->PB1,SIGNAL(clicked()),this,SLOT(on_PB1_clicked()));
ui->PB1->setText("Start");
thread1->closeThread();
thread1->wait();
}
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