Re: Worker thread in VC++ 6
Here is what I have with some explanations:
Now you can rip me apart with my bad coding (this is why I am asking so I
can fix).
After the 33 bytes is received I need to send it to the main Dlg
UpdateDisplay() so it updates the bargraph with the received data.
At the top of Martin1Dlg.cpp I have:
---------------------------------------------------------
#include "stdafx.h"
#include "Martin1.h"
#include "Martin1Dlg.h"
#include "BarChart.h"
#include "CCdrvPPPort.h"
unsigned char Bar[40];
int ComPort = 1; //COM port number
CCdrvPPPort Port; //Port object
UINT WorkerThreadProc( LPVOID Param );
void CMartin1Dlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CMartin1Dlg)
//}}AFX_DATA_MAP
DDX_Control(pDX, IDC_BARCHART, m_BarChart);
}
BOOL CMartin1Dlg::OnInitDialog()
{
CDialog::OnInitDialog();
SetIcon(m_hIcon, TRUE);
SetIcon(m_hIcon, FALSE);
Port.SetBaudrate(19200);
Port.SetParity(ParityNone);
Port.SetCharacterLength(8);
Port.SetNumberOfStopbits(1);
Port.OpenPort(ComPort);
AfxBeginThread(WorkerThreadProc,NULL,THREAD_PRIORITY_NORMAL,0,0,NULL);
return TRUE;
}
void CMartin1Dlg::OnButton1() //When Button1 is clicked it shows a test
Bargraph of 33 bars
{
int i;
m_BarChart.SetNumData(33); //33 is how many bars to display
for (i=0;i<33;i++)
{
m_BarChart.SetData(i,0x01); //SetData is the actual bar number(i) and
data for the bar(0x01)
}
m_BarChart.Invalidate();
}
void CMartin1Dlg::UpdateDisplay()
{
m_BarChart.SetNumData(33); //33 is how many bars to display
for (i=0;i<33;i++)
{
m_BarChart.SetData(i,Bar[i]); //SetData is the actual bar number(i) and
data for the bar(Bar[i]])
}
m_BarChart.Invalidate();
}
UINT WorkerThreadProc( LPVOID Param ) //Worker thread to read serial port if
data come in
{
int DataByte=0x00;
int Count=0;
loop:
while(Count == 0){
Count = Port.BytesInReceiveBuffer();
Sleep(100);
}
DataByte=Port.GetByte(18); //18 is the timeout in 18ths of a second
(never takes that long)
if (DataByte == 0xfe){
for (i=0;i<33;i++) //read 33 more bytes after 0xfe
{
DataByte=Port.GetByte(18); //18 is the timeout in 18ths of a second
Bar[i]=DataByte;
}
goto loop; //don't I need to go back into the loop to
keep checking port?
return TRUE; //here because the function needs to return
value
}
=====================================================================================
"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:uqjkr3lbrsp3llvl7avpd71a3ci9bs2796@4ax.com...
Many problems here
See below...
On Tue, 19 Feb 2008 01:08:21 GMT, "Kahlua" <kahlua@right.here> wrote:
I have the following code below that apears to be working.
I have not included all the serial port initialization here.
When I receive a 30h or 31h or 32h into the serial port it does display
the
correct "Got ##h" message.
Now how do I get the data (Bar[0]) to "UpdateDisplay()" ?
Bar[] is a global varible;
I checked the task manager and I do not seems to be wasting any CPU
cycles.
Thanks
=================================================================
void CMartin1Dlg::UpdateDisplay()
{
m_BarChart.SetNumData(33);
m_BarChart.SetData(1,Bar[0]);
****
The use of a global variable is contraindicated here. Do not use a global
variable like
this. You have provided no synchronization, and it is pointless to use a
global variable.
You are thinking single-threaded in a multithreaded environment. A global
variable would
be a Bad Idea in a single-threaded environment, and it is potentially a
disaster in a
multithreaded environment. You have not specified what the purpose of
SetNumData is, or
what the significance of 33 is, or what SetData does, or why it does it.
Lacking all
these pieces of information, it is impossible to guess what the interface
to this code
*should* be.
****
m_BarChart.Invalidate();
}
UINT WorkerThreadProc( LPVOID Param ) //Sample function for using in
AfxBeginThread
{
int DataByte=0x00;
int Count=0;
loop:
while(Count == 0){
Count = Port.BytesInReceiveBuffer();
Sleep(100);
}
****
Polling every 100ms. This imposes an unnecessary delay and limits your
throughput. Also,
it only says there is *some* data there; it doesn't say if there is
*enough* data there!
What does "18" mean?
As already pointed out, NOT EVEN FOR TESTING PURPOSES, do not call
AfxMessageBox in a
worker thread. If you want to see some output, use the TRACE() macro.
If you want to update the data, you have a complete and total disaster
here. For example,
supposed you get byte 0x30. You will not be allowed to read another byte
UNTIL THAT
INFORMATION IS DISPLAYED, and by using a global variable, you absolutely
guarantee that
you will lose data, because if you don't display the 0x30 by the time the
next byte is
read, perhaps a fraction of a millisecond later, you lose it.
What is your data rate? The 100ms delay suggests the rate is very low.
So the correct
solution would be
BOOL running = TRUE;
while(running)
{ /* read loop */
BYTE buffer;
DWORD bytesRead;
BOOL b = ReadFile(serial, &buffer, 1, &bytesRead, NULL);
if(!b)
{ /* failed */
DWORD err = ::GetLastError();
if(err != ERROR_IO_PENDING)
{ /* actual device error */
wnd->PostMessage(UWM_IO_ERROR, (WPARAM)err);
continue;
} /* actual device error */
switch(::WaitForMultipleObjects(waiters, 2, FALSE, INFINITE)
{ /* wfmo */
case WAIT_FAILED:
default:
err = ::GetLastError();
ASSERT(FALSE);
running = FALSE;
continue;
case WAIT_OBJECT_0:
running = FALSE;
continue;
case WAIT_OBJECT_0 + 1:
break;
} /* wfmo */
} /* failed */
else
{ /* succeeded */
if(bytesRead == 0)
continue; // timed out successfully
} /* succeeded */
wnd->PostMessage(UWM_DATA, (WPARAM)buffer);
} /* read loop */
The business about the waiters and the WFMO are as outlined in my essay.
Since you only
care about one byte at a time, this is the simplest approach.
UWM_IO_ERROR and UWM_DATA
are user-defined messages as per my essay on message handling.
LRESULT CMyClass::OnData(WPARAM wParam, LPARAM)
{
BYTE b = (BYTE)wParam;
... do something with b
Invalidate();
return 0;
}
Note that you may not be invalidating the CMyClass (which would be a
CView-derived class,
for example) but may be invalidating some control (e.g., a CStatic) in a
dialog.
Note that you may receive a hundred OnData messages before any attempt is
made to redraw,
so you cannot overwrite anything, that is, the OnDraw/OnPaint handler must
*not* depend on
the value in some 1-byte buffer, because that data may be overwritten a
hundred times
before the drawing gets a chance to get done.
****
DataByte=Port.GetByte(18);
if (DataByte == 0x30){
Bar[0]=0;
AfxMessageBox("Got 30h");
}
if (DataByte == 0x31){
Bar[0]=10;
AfxMessageBox("Got 31h");
}
if (DataByte == 0x32){
Bar[0] ;
AfxMessageBox("Got 32h");
}
goto loop;
****
What in the world is a 'goto'? Why would you use one in a real program?
Especially one
for which it is completely inappropriate. When goto is used, it must be
carefully thought
out, and this is a very good example of the misuse of a goto. It should
not be needed
here.
joe
****
return TRUE;
}
Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm