Can a USB device have a low bandwidth because of poor connection?

Question

I found in the garbage an old USB webcam with an OV 518 chip. The USB cable that was going out of it, however, wasn't there. There were just some remains of the tiny red/white/green/black wires that are usually inside the USB cable. I do not know why, but there are two copies of the black wire.

Therefore I made a very quick contact (without tin, just by doing some knots) with a USB cable that I had cut in half. You can see it in the following picture: .

The camera is recognized by my computer (I use Mac OS X and macam ), but it complains that it has "not enough bandwith" and cannot do any acquisition.

Now, my question.

I do not know anything about the camera and it might well be that it is faulty for its own reasons, in which case I would return it to the garbage. But could it be that the bandwidth is low because of the horrible, handmade, connection? I do not know the USB standard so I do not know if the bandwidth depends on the quality of the connection. Is there a way, such as a software utility, to check the quality of a USB connection? If this is the case, I guess I could try to do a better connection and make it work.

EDIT: Now I have soldered the wires, so I made a stronger connection. The problem persists exactly as before

Answer 1

The bandwidth message has to do with high-layer communications protocols. If you get that message, it means the physical layer works, but something is wrong at the protocol layer. Perhaps there's a bug in the camera, and that's why you could "find" it?

There is also a very small chance that the D+ and D- wires are reversed, which would cause the camera to be detected as low-speed when it should be full-speed. If the other option is to throw away the camera, you could try switching D+ and D- and see if it works any better, although I would give it a pretty low chance.

Answer 2

What do you mean 'two copies of the black wire'?

USB uses a voltage differential (3-wire) data bus cable with grounded shield to minimize interference from external sources. Your unexposed wires and unsoldered connections could be a source of noise.

With regard to thee bandwidth error, the macam FAQ mentions lowering image format frame rate. Did you try this?

There is also a bandwidth slider in the video settings dialog which can be adjusted to restrict the USB bandwidth.

You may also find this article of interest, in that it describe a problem with the way Mac OSX hands out USB bandwidth to isochronous devices.

For monitoring performance of your USB ports, the iStats Menu tool offers a range of status statistics including bandwidth performance.