Talking to a USB GPS device - C / C++ / MFC Discussion Boards

Re: DLL to VB callback help

borono9-Apr-06 4:35

borono

9-Apr-06 4:35

haha, no worries. I do have it working, here is what I did.

DLL Side:


#include <comdef.h>

template< class T >
BSTR ToBSTR( T a_Str )
{
     return( _bstr_t(a_Str).copy() ) ;
}


extern "C" void __stdcall stat( void (*cb) (u_short**) )
{
		char dao[100];  //way too much is better than way too little
	        sprintf(dao,"UDP: %d",udp); //do the work here, your faster
		BSTR l_Temp = ToBSTR(dao); // convert to BSTR
		BSTR bs = SysAllocString ( l_Temp ); //make it
		cb( &bs );  //send it
		SysFreeString ( bs ); //free it
		bs = NULL; //null it
}

VB Side:

Declare Sub stat Lib "mydll.dll" (ByVal funcptr As Long)
'
Sub CallbackFunction(ByRef numb As String)
    Form1.Label1.Caption = numb
End Sub

works great! computer saved. Smile | :)

best regards

-- modified at 10:37 Sunday 9th April, 2006

EDIT: thought it would be a good idea to include the conversion function, considering without it, this code is useless. Bold represents the modificiation.

Re: DLL to VB callback help

Waldermort9-Apr-06 4:52

Waldermort

9-Apr-06 4:52

borono wrote:
haha, no worries. I do have it working,

Damnit, I just put my shoes on too. Congrats, you spent long enough on this, now you can move onto the next problem :P

Re: DLL to VB callback help

borono9-Apr-06 8:20

borono

9-Apr-06 8:20

haha, how'd you know I'd be having a problem? I am, but it is all design. This I really am horrible with. When it comes to design, you will see many programmers all designing their GUIs pretty much the same way. Not because there is a lack of creativity but because it works. There is indeed, at least, three ways to accomplish anything. They have found the first, I am concerned with the latter. Wink | ;)

best regards

Thread is frozen

LionAM8-Apr-06 12:51

LionAM

8-Apr-06 12:51

Hello!

In my program I have something like this:

<br />
volatile stop;<br />
<br />
void SetStop()<br />
{<br />
  stop = true;<br />
  while (stop) Sleep(100);<br />
}<br />
<br />
//Thread:<br />
while (true)<br />
{<br />
  if (stop) <br />
  {<br />
    stop = false;<br />
    return;<br />
  }<br />
  Sleep(10);<br />
}<br />

But while the main thread waits for the
variable stop to be reset, this never
happens! Why not?
If I don't wait for it, the program opens
a message box (which sais that the thread
was not stopped; by use of a CSingleLock),
and when it is open, the thread resumes...

Alex

Re: Thread is frozen

includeh108-Apr-06 19:07

includeh10

8-Apr-06 19:07

try to change as:
bool stop=false;

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Re: Thread is frozen

Philipps8-Apr-06 20:13

Philipps

8-Apr-06 20:13

You forgot the variable type, bool is ok. So add bool after volatile;

volatile bool stop;

Re: Thread is frozen

LionAM8-Apr-06 20:58

LionAM

8-Apr-06 20:58

Thank you for your answer.
I only forgot it in my question, that's not the problem.
I also used the Debugger to go through the code.
But when I use "Run to Cursor" within the Thread-Loop
or set an breakpoint when I entered the waiting loop,
it never gets called.

Alex

Talking to a USB GPS device

smikesmith8-Apr-06 12:23

smikesmith

8-Apr-06 12:23

I'm doing a hands-on learning process to communicate with a USB-GPS unit (specifically a Garmin GPS-18USB). I've searched a number of sources including Garmin's "SDK", and have figured out how to talk the language. I can manually get PVT info from the unit, etc., but would now like to move to the next step, that is, to make an MFC-based program "drive" the unit and display the data. The unit outputs data every second when instructed to do so.

I open the channel with CreateFile to produce a handle, and DeviceIoControl. I can send commands to the unit and receive data back. But I don't understand how to deal with asynchronous data and leave the GUI operating normally, that is, if I'm unsure when/if data may be received, I can't just call a Read or DeviceIoControl function: it will never return if there's no data available. I believe I need a worker thread to gather the data, but therein lies a problem:

How does one determine if data is available for a Read operation, read it, then get it back to the main app periodically for display? What's the right technique for managing this, knowing that perhaps the application may be asked to stop or close during a period that a Read operation is awaiting input? What functions may be used to allow a thread to be non-blocking, to respond to other messages?

Re: Talking to a USB GPS device

Iain Clarke, Warrior Programmer8-Apr-06 12:54

Iain Clarke, Warrior Programmer

8-Apr-06 12:54

Have a look at overlapped i/o (the last param in createfile , readfile etc).

You can then wait on events (read happened, thread should die, etc) in your worker thread.

Them when something interesting has been sent by the GPS unit, you can assemble it in your thread, and use PostMessage to kick your UI thread...

I know that's a short version....

Iain.

Re: Talking to a USB GPS device

smikesmith8-Apr-06 13:00

smikesmith

8-Apr-06 13:00

Thanks,
I've already tried the overlapped IO, so I guess I should use WaitForMultipleObjects: 1. the read complete and 2. the thread ends, etc.? I'm thinking that just waiting for a single object (the read happened) would still hang up?? Or will WaitForSingleObject@0mS in some kind of loop work?

Re: Talking to a USB GPS device

Iain Clarke, Warrior Programmer8-Apr-06 13:07

Iain Clarke, Warrior Programmer

8-Apr-06 13:07

What I've done is:

HANDLE hEvents [2];

...

hEvent [0] = Overlapped.hEvent;
hEvent [1] = hBailFromThread;

dwWait = WaitForMultipleEvents (hEvent, 2, INFINITE);

if (dwWait == WAIT1)
{
tidy up
return
}

do stuff ()
loop back.

and so on.

and to kill the thread:

SignalEvent (hBail);
WaitForSingleEvent (hThread, sensibletime);

etc.

I hope thatb helped a little.

Iain.#

Re: Talking to a USB GPS device

smikesmith8-Apr-06 13:15

smikesmith

8-Apr-06 13:15

Gracious thanks for the quick replies. That makes sense (I think Smile | :)

) and I'm going to give it a go tomorrow. I'll note if I get it working...

Mike

Question about char* and __int32

big_denny_2008-Apr-06 11:43

big_denny_200

8-Apr-06 11:43

Hi all

I have such code :

...
__int32 x = 0;
char *str = "1234";

x = (str[0],str[1],str[2],str[3]);
...

What will be the value of x and why ?

thank you in advance

Re: Question about char* and __int32

Michael Dunn8-Apr-06 12:02

Michael Dunn

8-Apr-06 12:02

Homework?

x will be 52. Your turn - deduce why this is the case.

--Mike--
Visual C++ MVP Cool | :cool:

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Re: Question about char* and __int32

big_denny_2008-Apr-06 23:23

big_denny_200

8-Apr-06 23:23

Thanks for reply Mike, but it is not a homework.

I also know that x will be 52, but why ?

Re: Question about char* and __int32

Taka Muraoka9-Apr-06 3:36

Taka Muraoka

9-Apr-06 3:36

Look up how the comma operator works.

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How to paint from a memory DC to another memory DC

Axonn Echysttas8-Apr-06 7:12

Axonn Echysttas

8-Apr-06 7:12

I got the following problem: I got a DC in which I need to put an image comprised of more bitmaps. However, if I paint the bitmaps one by one, I get some flicker.

So I need 1 memory DC to paint the bitmaps with. 1 memory DC to paint them in. And then this last memory DC will get bitblt-ed on the third and real DC.

But the problem is that when I can't paint from the first DC to the second. I select the bitmaps in the first DC and bitblt them in the second. But when I do my stuff and bitblt the second DC upon the third, I get only white. Anybody got any clue what I'm messing up here?

I didn't include code 'cause my routine is rather complicated and it's not written in C++ but here is something that may be of use:
1. I create both memory DCs using "CreateCompatibleDC(REALDC)".
2. I select bitmaps in the first DC using "SelectObject (hdcMemory, myBITMAP)".
3. I simply bitblt from first DC to second DC at the desired coordinates.
4. I repeat steps 2. and 3. for 4 images, bitblt-ed at various coordinates within the second DC.
5. Now I bitblt the second DC in the real DC, the third one, the visual source.

All is white................

-= E C H Y S T T A S =-
The Greater Mind Balance

Re: How to paint from a memory DC to another memory DC

includeh108-Apr-06 7:34

includeh10

8-Apr-06 7:34

can u BitBlt() first memory DC to real DC properly?

default size of memory DC is 1x1 pixels.
did u set suitable size for all other memory DCs?

Re: How to paint from a memory DC to another memory DC

Axonn Echysttas8-Apr-06 9:15

Axonn Echysttas

8-Apr-06 9:15

I can't paint directly to the real DC 'cause I need to put more images. So I need an intermediate DC in which to dump the pictures piece by piece and then bitblt in the original DC.

I set the size of the memory DC by selecting a bitmap of the desired size in it. Is that correct.

-= E C H Y S T T A S =-
The Greater Mind Balance

Re: How to paint from a memory DC to another memory DC

includeh108-Apr-06 19:02

includeh10

8-Apr-06 19:02

do u know the differece between testing and final program?

Re: How to paint from a memory DC to another memory DC

Axonn Echysttas8-Apr-06 22:05

Axonn Echysttas

8-Apr-06 22:05

I don't know what you're trying to suggest here and I don't think I'm gonna like the sound of it. But please, give it a shot ::- ).

-= E C H Y S T T A S =-
The Greater Mind Balance

Re: How to paint from a memory DC to another memory DC

Iain Clarke, Warrior Programmer8-Apr-06 12:59

Iain Clarke, Warrior Programmer

8-Apr-06 12:59

Not a direct reply, but you should look at Image Viewer Utility[^] by PJ Arends. It should help you a lot while debugging the problem.

My guess is that you have incompatible bitmaps selected into your DCs.

Client Area not repainted after restore from minimization (still not solved)

naal118-Apr-06 6:44

naal11

8-Apr-06 6:44

Hi
I'm drawing a bitmap in the client area. However, after restoring from being minimized the client area is not repainted (non client area is shown). My guess is that WM_PAINT is not send, but why? I thought after WM_SIZE (which is received) WM_PAINT is send automatically. I even tried to force the repainting in WM_SIZE but that doesnt work either (or maybe i forced it the wrong way...). Please help Smile | :)

here's some code:

Creating the Window:

WNDCLASSEX wc;

wc.cbSize = sizeof(WNDCLASSEX);
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = ::GetModuleHandle(NULL);
wc.hIcon = LoadIcon(GetModuleHandle(NULL), MAKEINTRESOURCE (ID_ICON_SLICE_32));
wc.hIconSm = (HICON)LoadImage (GetModuleHandle(NULL), MAKEINTRESOURCE(ID_ICON_SLICE_16), IMAGE_ICON, 16, 16, 0);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wc.lpszMenuName = NULL;
wc.lpszClassName = g_szClassName;

g_hWnd = CreateWindowEx(
0,
g_szClassName,
"SliceEdit v0.1",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, g_Width, g_Height,
NULL, NULL, GetModuleHandle(NULL), NULL);

// in winproc DefWindowProc deals with WM_SIZE
...
case WM_PAINT:
PAINTSTRUCT PS;
HDC hDc = BeginPaint(m_hWnd,&PS);
SetDIBitsToDevice (hDc, 0, 0, w, h, 0, 0, 0, h, m_pBits, &m_BMI, DIB_RGB_COLORS);

EndPaint(m_hWnd,&PS);

-- modified at 15:39 Saturday 8th April, 2006

Re: Client Area not repainted after restore from minimization

includeh108-Apr-06 7:08

includeh10

8-Apr-06 7:08

wc.style=CS_HREDRAW|CS_VREDRAW;

Re: Client Area not repainted after restore from minimization

naal118-Apr-06 7:15

naal11

8-Apr-06 7:15

thanks, but didn't work Frown | :(

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