CPU comsuption with Serial Port Thread - c++

Question

I write my professional application and I have one problem with the serial port thread.
I have cpu consuption. When I add SerialCtrl.h (from project SerialCtrl http://www.codeproject.com/Articles/99375/CSerialIO-A-Useful-and-Simple-Serial-Communication ) in my project my CPU % is become more 100% so without is near 40%.
I use VS C++ 2012 Professional in ANSI 32 bits MFC MT
SerialCtrl.cpp
const unsigned short MAX_MESSAGE = 300;
IMPLEMENT_DYNCREATE(SerialThread,CWinThread)
SerialThread::SerialThread() :m_serialIO(NULL)
{
}
SerialThread::~SerialThread()
{
m_serialIO = NULL;
}
BOOL SerialThread::InitInstance()
{
return TRUE;
}
int SerialThread::Run()
{
// Check signal controlling and status to open serial communication.
while(1)
{
while(m_serialIO->GetProcessActivateValue()==TRUE)
{
if ((serialCtrl().GetPortStatus()==FALSE)&&m_serialIO->GetPortActivateValue()==TRUE)
{
if(serialCtrl().OpenPort(m_serialIO->m_DCB,m_serialIO->m_strPortName)==TRUE)
{
m_serialIO->OnEventOpen(TRUE);
}
else
{
m_serialIO->OnEventOpen(FALSE);
m_serialIO->SetPortActivate(FALSE);
}
}
else if (m_serialIO->GetPortActivateValue()==TRUE)
{
char message[MAX_MESSAGE]={0};
unsigned int lenBuff = MAX_MESSAGE;
unsigned long lenMessage;
if(serialCtrl().Read(message,lenBuff,lenMessage)==TRUE)
{
if(lenMessage>0)
m_serialIO->OnEventRead(message,lenMessage);
}
else
{
m_serialIO->SetProcessActivate(FALSE);
}
}
if (m_serialIO->GetSendActivateValue()==TRUE)
{
unsigned long nWritten;
if(serialCtrl().Write(m_serialIO->m_sendBuffer,m_serialIO->m_sendSize,nWritten)==TRUE)
{
m_serialIO->OnEventWrite(nWritten);
}
else
{
m_serialIO->OnEventWrite(-1);
}
m_serialIO->SetSendActivate(FALSE);
}
if (m_serialIO->m_bClosePort==TRUE)
{
if (serialCtrl().ClosePort()==TRUE)
{
m_serialIO->OnEventClose(TRUE);
}
else
{
m_serialIO->OnEventClose(FALSE);
}
m_serialIO->m_bClosePort=FALSE;
}
}
break;
}
return 0;
}
void SerialThread::ClosePort()
{
serialCtrl().ClosePort();
}
I guess that it is SerialThread run which an issues but I didn't find how solve it.
(After performance and others tools)
Are you some idea?
Thank you

Answer 1

I took a look at your code, and unfortunately the problem comes from the library/project you are using. Basically the all-in-one thread is just looping and never waiting anywhere, and this leads to 100% CPU consumption.
What you can do :
Add a Sleep(1-10) at the end of the inner while loop in the run() method. This method is the worst, it just patch the underlying problem.
Use another, better designed library.
Make your own library suited to your use.
Some advises to make your own serial com wrapper :
Everything you need to know about serial ports on Windows is here : Serial Communications.
An IO thread should always wait somewhere. It can be on a blocking IO call like ReadFile(), or on a Windows waitable object.
If you can, use overlapped IO, even if you don't use asynchronous calls. It will enable simultaneous read and write, and make the reads and writes cancellable (cleanly).
You only need a separate thread to read. And optionally another one to write via a message queue, if you want a completely asynchronous library.