error while loading shared libraries: libmpfr.so.4: cannot open shared object file 在Ubuntu22上编译QT出现这个错误error while loading shared libraries: libmpfr.so.4: cannot open shared object file加载共享库时出错：libmpfr.so.4:无法打开共享对象文件：没有这样的文件或目录解决办法：sudo ln -s /usr/lib/x86_64-linux-gnu/libmpfr.so.6 /usr/lib/x86_64-linux-gnu/libmpfr.so.4

Linux通用串口数据接收代码 #include <iostream> #include <thread> #include <mutex> #include <termios.h> #include <string.h> #include <poll.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <errno.h> #include <string.h> #include <signal.h> #include <pthread.h> using namespace std; int fd; void serial_read() { int nread; int BUFSIZE = 1024; unsigned char buff[BUFSIZE]; unsigned char *pbuff = NULL; struct timeval tv; fd_set rfds; tv.tv_sec = 2; tv.tv_usec = 0; while (true) { FD_ZERO(&rfds); FD_SET(fd, &rfds); if (select(1 + fd, &rfds, NULL, NULL, &tv) > 0) { if (FD_ISSET(fd, &rfds)) { pbuff = buff; nread = read(fd, buff, BUFSIZE); printf("Recv Len = %d\n", nread); for (int i = 0; i < nread; i++) { printf("0x%x ", buff[i]); } printf("\n"); memset(buff, 0, sizeof(buff)); } } } } int main() { if ((fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NONBLOCK)) < 0) { printf("err: can't open serial port!\n"); return -1; } struct termios options; tcgetattr(fd, &options); bzero(&options, sizeof(options)); options.c_cflag |= B115200 | CLOCAL | CREAD; options.c_cflag &= ~CSIZE; options.c_cflag |= CS8; options.c_cflag &= ~CSTOPB; options.c_cflag &= ~PARENB; tcflush(fd, TCIOFLUSH); if (tcsetattr(fd, TCSANOW, &options) != 0) return -1; thread th(serial_read); th.join(); return 0; }

QT-利用Qcamera查看USB摄像头参数(数据帧格式+分辨率) 运行环境检查：首先检查自己的QT版本及系统环境是否支持Qcamera：Qcamera是multimedia模块中的接口函数，multimedia模块在QT5.3之后是自带的。在windows环境下可直接使用，在LINUX 环境下需要手动安装multimedia模块。代码片段：pro文件包含：QT += multimedia multimediawidgets示例#include "mainwindow.h" #include "ui_mainwindow.h" //相机相关的头文件 #include <QCamera> #include <QCameraInfo> #include <QVideoProbe> MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow) { ui->setupUi(this); m_camera = new QCamera(this);//初始化摄像头设备 QVideoProbe *m_pProbe = new QVideoProbe; if(m_pProbe != nullptr) { m_pProbe->setSource(m_camera); // Returns true, hopefully. connect(m_pProbe, SIGNAL(videoFrameProbed(QVideoFrame)),this, SLOT(slotOnProbeFrame(QVideoFrame)),Qt::QueuedConnection); }//其中SIGNAL(videoFrameProbed(QVideoFrame)为VideoProbe模块自带的信号 m_camera->setCaptureMode(QCamera::CaptureViewfinder);//设置捕捉模式为视频 m_camera->setViewfinder(ui->centralWidget);//设置 摄像头画面的显示位置 m_camera->start();//开启摄像头 //查询摄像头支持的分辨率 QList<QSize> sizes = m_camera->supportedViewfinderResolutions(); qDebug() << "viewfinderResolutions sizes.len = " << sizes.length(); foreach (QSize size, sizes) { qDebug() << "Resolutions size = " << size; } //摄像头参数初始化，根据需求用户自定义摄像头分辨率,也可以用来设置摄像头数据类型 QCameraViewfinderSettings set; set.setResolution(VIDEO_WIDTH, VIDEO_HEIGHT);//设置分辨率 //set.setPixelFormat(QVideoFrame::Format_YUYV); //设置像素格式 Android上只支持NV21格式 m_camera->setViewfinderSettings(set); //包含头文件QCameraInfo QList<QCameraInfo> cameras = QCameraInfo::availableCameras();//获取可用摄像头设备列表 foreach (const QCameraInfo &cameraInfo, cameras) { qDebug()<<"检测到设备："<<cameraInfo.deviceName();//摄像头的设备名称 } } //图像触发的槽函数 void MainWindow::slotOnProbeFrame(const QVideoFrame &frame) { QVideoFrame cloneFrame(frame);//类拷贝操作，fram -> clonframe cloneFrame.map(QAbstractVideoBuffer::ReadOnly); //视频缓冲区数据映射到系统内存 //unsigned char rgb_buffer[VIDEO_WIDTH*VIDEO_HEIGHT*3]; qDebug()<<"设备数据格式："<< cloneFrame.pixelFormat()<<endl; cloneFrame.unmap(); } MainWindow::~MainWindow() { delete ui; }

C语言：获取程序运行消耗的时间(gettimeofday) 对于普通的C程序：#include<stdio.h> #include<sys/time.h> //注意引用这个头文件 #include<unistd.h> int delay(int time) { //这里用来表示你自己要运行的程序 } int main() { //定义两个结构体，来记录开始和结束时间 struct timeval start; struct timeval end; //记录两个时间差 unsigned long diff; //第一次获取时间，即表示开始记时 gettimeofday(&start,NULL); //运行自己的程序 delay(10); //第二次获取时间，即表示结束记时 gettimeofday(&end,NULL); //计算时间差，并打印 diff = 1000000 * (end.tv_sec-start.tv_sec)+ end.tv_usec-start.tv_usec; printf(“thedifference is %ld\n”,diff); return 0; }对于内核模块的C程序#include<stdio.h> //注意引用这个头文件 #include<linux/time.h> #include<unistd.h> int delay(int time) { //这里用来表示你自己要运行的程序 } int main() { //定义两个结构体，来记录开始和结束时间 struct timeval start; struct timeval end; //记录两个时间差 unsigned long diff; //第一次获取时间，即表示开始记时 do_gettimeofday(&start,NULL); //运行自己的程序 delay(10); //第二次获取时间，即表示结束记时 do_gettimeofday(&end,NULL); //计算时间差，并打印 diff = 1000000 * (end.tv_sec-start.tv_sec)+ end.tv_usec-start.tv_usec; printf(“thedifference is %ld\n”,diff); return 0; }

QT--程序收不到组播数据 主要需要设置组播网卡 QString strName = ui->comboBox_network->currentData().toString(); interface = QNetworkInterface::interfaceFromName(strName); // 根据选择名称获取网卡 QByteArray data; tftudpsocket = new QUdpSocket(); tftsendaddres.setAddress("239.1.1.15"); tftudpsocket->bind(QHostAddress(ip), 6002, QUdpSocket::ShareAddress | QUdpSocket::ReuseAddressHint); //加入组播组 tftudpsocket->setSocketOption(QAbstractSocket::MulticastLoopbackOption, 0); //设置组播网卡 tftudpsocket->setMulticastInterface(interface); tftudpsocket->joinMulticastGroup(QHostAddress(tftsendaddres), interface); connect(tftudpsocket, SIGNAL(readyRead()), this, SLOT(read_tftdata())); //发送一个空数据出去 tftudpsocket->writeDatagram(data, QHostAddress(tftsendaddres), 6002);