串口如何稳定接收数据(转帖)
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http://www.qtcn.org/bbs/read-htm-tid-57104.html大家好我在用qt做串口调试工具时遇到类似的问题：卡的元凶找到了ui->textEdit->append(str);这句话，每次要刷新一次显示。现在该如何处理？这个没法放在别的线程处理吧.
本人的想法:
1.其实跟这个帖子的很类似，不一样的地方是用insert方式，因为append是自带换行的，跟我的想法有出入。
2.相信接触过串口调试助手的对AccessPort都不陌生，其实就是想做一个类似的串口接收工具，发现qt做起来很难,许多网友一直在怀疑我要做到工具的有效性(1ms帧与帧间隔，不停的发送数据)，其实工具做出来肯定是有用的,就看个人需不需要。AccessPort的优越性就是,发送过来的数据不管多快都能显示出来，并且不影响界面的移动，界面其他按钮的操作，都非常的流畅。但是qt做的串口调试助手如果接收1ms,大约100字节左右发送过来的数据，界面肯定卡死(不能执行任何操作)，我最近在网上一直找qt版的串口调试助手，没有一个能抗住这个测试,qt自带的demo也一样。
初步怀疑：由于数据量比较大，qt文本显示控件是全部更新导致时间长，导致主ui延缓，导致界面卡死，不能移动，不能操作界面上的任何按钮。
确诊:经过多次询问网友，最终确认为显示控件显示数据量大，刷新缓慢导致。
确认之前本人已经尝试过的方法如下:
1.换qt自带有关文本控件,问题不能解决。
2.用缓存+延时的方法，时间久照样会卡，并且实时性很差，A串口发送工具已经发送数据完毕，自己编写的串口工具还是慢慢的显示数据。
3.线程的方法，本人一直用的就是线程，一个线程接收串口过来的数据，然后再投递给显示控件,还是不能解决问题。
4.有网友说用qapplication::processevent，在显示槽函数中加入一对该函数，也不行，时间长(1分钟左右)照样有问题
5.想用重绘的方法，不止从何下手.尤其是重绘文本+滚动条，由于本人是初学者。对qt 有一定的了解，但是遇到这种问题真不知道如何解决。
6.国外论坛查找相关解决方法，在google上好像也有老外问过类似的问题。具体链接忘记，但是也没有具体的解决方法。
希望奇能异士能帮忙解决此问题，很多人都觉得很简单，不屑一看，其实我就是想说，问题感觉不是想象中的简单，可能我是初学者的原因。学习qt一年来，觉得初学的资料不少，但是到深入的就没有啦，资料太少啦。越来越觉得没有信心学好，请网友们勿劈砖。希望得到大家的帮助。 -
- You use debug build or release build?
- Did you perform profiling on ui->textEdit->append(str) ?
- write a program that only involve ui->textEdit->append(str) to perform profiling.
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hi Vincent007
1.debug build
2.Yes,The refresh speed is very quick, not a bit dull, but I don't like with append, because append broken the original data format, especially the received data is Chinese。The original format:
你好！
我很认真，但是很失望。一直再等待。
If you use the append may become the following format：
你好！
我很认真，
但是很失望。
一直再等待。
3.I once did a test, use a non UI thread interval 1ms to control sending data, display data using insert, long time after will refresh is not over, the main UI can't move。
4.I think QT is text controls render caused by slow。Thank you for your reply！
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What is release build performance?
Did you test release build? -
hi Vincent007
1.I have done a test release version using append fast.no problem。
2. but I don’t like to use append, because append broken the original data format, especially the received data is Chinese。The original format:
你好！
我很认真，但是很失望。一直再等待。
If you use the append may become the following format：
你好！
我很认真，
但是很失望。
一直再等待。
Thank you for your reply -
hi Vincent007,JohnYork
我已经把代码上传到如下链接，同时里面有一个测试视频，qt5.3.1 mingw编译的
http://pan.baidu.com/s/1kTh0ifd
。
谢谢你们的讨论。 -
試把
@
connect(
&m_Portconfigview,SIGNAL(signalConfigPort(const SPortsettings *)),&m_Serialportrecevie,SLOT(slotsConfigPort(const SPortsettings *)),Qt::QueuedConnection);
connect(
&m_Portconfigview,SIGNAL(signalConfigPort(const SPortsettings *)),this,SLOT(updatetstatus(const SPortsettings *)));
connect(
&m_Serialportrecevie,SIGNAL(signalThreadToStore( const QByteArray&)),&m_Serialportcachedata,SLOT(slotsSerialportcachedata(const QByteArray&)),Qt::BlockingQueuedConnection);
connect(
&m_Serialportcachedata,SIGNAL(signalToserialportwindow(const QByteArray&)),&m_pSerialPortWindow,SLOT(slotsserialportupdateview(const QByteArray&)),Qt::BlockingQueuedConnection);
@
改成
@
connect(
&m_Portconfigview,SIGNAL(signalConfigPort(const SPortsettings *)),&m_Serialportrecevie,SLOT(slotsConfigPort(const SPortsettings *)));
connect(
&m_Portconfigview,SIGNAL(signalConfigPort(const SPortsettings *)),this,SLOT(updatetstatus(const SPortsettings *)));
connect(
&m_Serialportrecevie,SIGNAL(signalThreadToStore( const QByteArray&)),&m_Serialportcachedata,SLOT(slotsSerialportcachedata(const QByteArray&)));
connect(
&m_Serialportcachedata,SIGNAL(signalToserialportwindow(const QByteArray&)),&m_pSerialPortWindow,SLOT(slotsserialportupdateview(const QByteArray&)));
@ -
Did you test release build?
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measure time consumed by slotsSerialportcachedata and slotsserialportupdateview via QElapsedTimer
另外你要確保你的PC 沒有問題.你有否在另一台PC試過你的程序?
@
QElapsedTimer timer;
timer.start();
slowOperation1();
qDebug() << "The slow operation took" << timer.nsecsElapsed() << "nanoseconds";
@ -
HI Vincent007
前阵子忙别的去，所以今天才回复你，不好意思按照你说的用以下代码进行测试
timer.start();
pSerialPortQPlainTextEdit.insertPlainText(DatatFormRead);
pSerialPortQPlainTextEdit.moveCursor(QTextCursor::End, QTextCursor::KeepAnchor);
qDebug() << "The slow operation took" << timer.nsecsElapsed() <<"nanoseconds";
下面是测试结果:
The slow operation took 1017500 nanoseconds
The slow operation took 1018310 nanoseconds
The slow operation took 1421502 nanoseconds
The slow operation took 1186476 nanosecondsThe slow operation took 10685984 nanoseconds
The slow operation took 10668154 nanoseconds
The slow operation took 10564419 nanoseconds
The slow operation took 10569686 nanoseconds
The slow operation took 10243486 nanoseconds
The slow operation took 10473245 nanoseconds
The slow operation took 10746766 nanoseconds
The slow operation took 10772700 nanoseconds
The slow operation took 10583059 nanoseconds
The slow operation took 11221681 nanoseconds
The slow operation took 10795798 nanoseconds
The slow operation took 16827051 nanosecondsThe slow operation took 222369451 nanoseconds
The slow operation took 205003460 nanoseconds
The slow operation took 222164411 nanoseconds
The slow operation took 204823949 nanoseconds
The slow operation took 209414655 nanoseconds
The slow operation took 186572559 nanoseconds
The slow operation took 209589304 nanoseconds
The slow operation took 214433676 nanoseconds
The slow operation took 219041401 nanoseconds
说明qt的窗口刷新确实有问题，请指教谢谢。 -
@
#include "mainwindow.h"
#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
_timer.setInterval(10);for(int i = 0; i<1024;i++) { message += "1"; } connect(&_timer,&QTimer::timeout,this,&MainWindow::updateText); _timer.start();}
MainWindow::~MainWindow()
{
delete ui;
}void MainWindow::updateText()
{
ui->textEdit->append(message);
}
@
I did a simple application and test it. It works fine.
You can try it and adjust parameters.