2 USB Cameras on same bus

[MarkGreally]

Hi.

I have 2 usb cameras which work fine when plugged into seperate USB busses. I want to use multiple cameras with a usb hub and to lower the frame rate.  The default frame rate is 30 fps and the cameras work fine independantly at this speed. To try to get 2 devices working I have opened 2 NI-MAX windows. I have changed the video mode to 288x288 YUY2 7.5 fps. This is a substantial reduction. I do the same for the other camera in the other NI-MAX window but I get a timeout error 0xBFF6901B when trying to preview the second camera. Surely this should be able to handle both devices with the lowered speed.

Is this possible or does the bus not allow more than one camera device?

Thanks,

Mark.

[edjones93]

Hello Mark,

I am Ed from National Instruments Applications Engineering. I have been researching into your issue, for which I have found that this could still be beyond the capabilities of the hardware/software interface within the default timeout as USB Cameras interface via DirectX, as such this abstraction layer will incur processing time additionally to transmission time from the camera to the machine.

The first step I would recommend is to verify whether this issue persists for both the snap and grab operations. Additionally it would be useful to use a different PC/laptop to verify whether the issue is specific to the machine as the motherboard may have a different USB controller setup which could cause the issue as I have found with one previous case.

I have also noted that the available RAM could relate to the processing time which could incur the timeout, could you please provide the model number of the PC/laptop that you are using?

I was also able to locate the article linked below which clarifies much of what I have mentioned above, could you confirm also whether the provided example at the bottom of this article receives a timeout issue also:

http://digital.ni.com/public.nsf/allkb/d13527d8471d5fc5862576a4006bd081?OpenDocument

I hope that this is helpful and you are successful in your application.

Best regards,

Ed

[MarkGreally]

Hi Ed.

i have managed to get both working on the hub. Here is the weird bit. It was originally plugged into a USB 3.0 port which I thought would be the best. Then I changed it to the USB 2.0 port and hey presto it worked. I thought the 3.0 port would be faster and more suitable but I was wrong. The laptop I am using is a Leveno B590.

Regards,

Mark.