USBCamera won't disconnect from camera for GRIP to run

Technical Programming
1

I’m wanting to write the following code for our robot code:

Startup:

  • create USBCamera object
  • set the brightness and exposure from stored preferences
  • disconnect from camera
  • run GRIP

Currently when I try this, GRIP says that the frame grabber could not connect to the camera.

Here’s what I know so far:

  • I have created my own USBCamera class that is an exact copy of the WPI lib version, but gives me the ability to set the exposure with better control
  • The constructor for USBCamera calls openCamera() which calls NIVision.IMAQdxOpenCamera()
  • The USBCamera method closeCamera() calls NIVision.IMAQdxCloseCamera
  • I do not use the autocpature feature, I call getImage() and push that to the CameraServer object so startCapture() is never called.

I assumed that NIVision.IMAQdxCloseCamera() would close the connection to the camera, but that does not seem to be the case. I am calling that and then trying to start GRIP and grip fails connecting to the frame grabber for cam0 (the same camera I just used in USBCamera).

Does anyone have any idea how to do this? Any idea why calling USBCamera.closeCamera() does not disconnect from the camera object?

Thanks in advance

2

What model camera is it? For many types of USB cameras, the driver comes with a dashboard program that lets you persistently set things like brightness and exposure while it’s plugged into your laptop, then you can just move it over to the RIO.

Also, a lot of webcams have an LED that turns on when it’s connected. Can you verify that IMAQdxCloseCamera causes the LED to turn off?

3

I’m using the LifeCamHD. I did some more digging. You’re right about the light. It turns out that it IS disconnecting from the camera. GRIP is connecting to the camera. The exceptions I saw were anomalies. It turns out the real issue is this exception:

eb 06, 2016 4:27:56 PM edu.wpi.grip.core.operations.composite.PublishVideoOperation lambda$new$17
WARNING: Address already in use
java.net.BindException: Address already in use

So the closeCamera does actually disconnect (and you do see the blue light turn off). I’m going to move this discussion to a new thread that discusses the above issue.

4

As far as I can tell, A) there is no program that comes with the camera. It uses the USB standard camera interface. B) if you power the camera off, it loses it’s settings. I do have an app for controlling the settings from my laptop, but as soon as you unplug and re-plug, you lose the settings.