How to get USB ports connected to multiple cameras using C/C++ program?

>>When running the following program, it takes the same picture from the same camera.<<

Does it report a different device name and id each time? You could try a DoEvents/Sleep in the loop.

Also, try calling CommonDialog1.ShowSelectDevice to make sure each camera is supported.

>> how can I adjust its brightness. <<

I'd suggest breaking it up a bit and looking around.

Code:

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Set oDevice = DeviceManager1.DeviceInfos(i).Connect

' See what properties the device supports...
CommonDialog1.ShowDeviceProperties(oDevice)

Set oItem = oDevice.ExecuteCommand(wiaCommandTakePicture)

' See what properties the image supports...
CommonDialog1.ShowItemProperties(oItem)

Set oImage = oItem.Transfer
' or Set oImage = CommonDialog1.ShowTransfer(oItem)

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Both the device and the item support a properties collection so have a look around. the oItem represents the picture on the camera before it is downloaded to the computer. Have a look at the other methods on CommonDialog.

>>Does it report a different device name and id each time?

Yes, it reports ids:

Code:

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{...}\000;
{....}\007(I don't know why it is 007, probably according to the USB port. By the way, I have 8 USB ports on my computer);
{....}\002

---

Also, I can see the lights on the the three receivers flashed from red to green. So I am sure it functions from different channel.

Oh, I got a tricky problem now. When last time channel 1 cam is used in the webcam own software, the picture will be taken differently at the first two pictures. However, when last time channel 2 or 3 is used, the three pictures will be the same.


>>You could try a DoEvents/Sleep in the loop.
How can I write such a loop? Could you give me details?

Also, try calling CommonDialog1.ShowSelectDevice to make sure each camera is supported.

>>I'd suggest breaking it up a bit and looking around.
I will try your code.

Thank you so much

David

>>How can I write such a loop? Could you give me details?<<

Try adding this in the loop.

Code:

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' At top of module
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)

...

DoEvents
Sleep(1000) ' one second
DoEvents

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EDIT: I'm signing off for now.

I tried showing device properties, but all are not available, however, except one can't take picture properly, the other two take pictures correctly.

I will try the sleep next monday. I am not going to work more this week.

Thanks

David