PCCAM on bulk pipe??

NTDEV
1

Hi all,

Does anyone know how to implement PCCAM on bulk pipe instead of iso pipe?
I hear of ‘usbcamd.lib’ could support bulk pipe PCCAM without any
modification, but how do I use it in my minidriver? Farther, what’s
difference in device’s firmware? Could you help me?

Waiting for your messages! We may have a good discussion.

Best Regards,

Dengwen

2

xxxxx@sunplus.com.cn wrote:

Does anyone know how to implement PCCAM on bulk pipe instead of iso
pipe? I hear of ‘usbcamd.lib’ could support bulk pipe PCCAM without
any modification, but how do I use it in my minidriver? Farther,
what’s difference in device’s firmware? Could you help me?

USBCAMD supports the use of a bulk pipe for still images and downloads,
but streaming video is assumed to travel on an isochronous pipe.

There is no firmware difference between the two, except for the bit in
the descriptors that defines the type of pipe.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.

3

Thanks Tim! So we must simulate isochronous pipe on fireware using bulk
pipe, right? But there are another question: In iso mode we could send
hundreds bytes in one packet but only 64 btyes in bulk mode. So one image
frame will cause too many packets, and I have to deal with these packets
in CAM_ProcessUSBPacket routine, the cost will be horrible. Do you have
any idea about it?

Best Regards,

Dengwen

4

xxxxx@sunplus.com.cn wrote:

Thanks Tim! So we must simulate isochronous pipe on fireware using
bulk pipe, right?

The better solution is to change your firmware to use isochronous.
That’s usually a trivial change to the firmware – just change the
endpoint descriptor.

But there are another question: In iso mode we could send hundreds
bytes in one packet but only 64 btyes in bulk mode.

That’s true in USB 1.x, but not 2.x.

So one image frame will cause too many packets, and I have to deal
with these packets in CAM_ProcessUSBPacket routine, the cost will be
horrible. Do you have any idea about it?

Oh, come on. The cost is not “horrible”. So you get 15 calls to
CAM_ProcessUSBPacket instead of 1. The cost of the calls is trivial
compared to the cost of the copy, which will still have to be done.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.