How do I communicate with a GPIO USB device in OS X?

I have a USB web camera from ViMicro that contains a GPIO chip. We have a microswitch wired to one of the IO pins and can read the status of the switch on Windows using an ActiveX control that was provided by ViMicro, named exvmuvc.ax. I need to duplicate this functionality using IOKit on OS X.

USBTrace from SysNucleus displays the conversation happening between the Windows system and the USB device, but I cannot duplicate this on the Mac开发者_开发问答.

Does anyone know of a software USB sniffer, like USBTrace, that works on OS X so that I can compare the packets? Also, is anyone familiar with this particular camera chip and its GPIO subsystem, even on Linux?

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You could use usbtracer from Xcode, or you can try using using USB Prober with a debug release of IOUSBFamily, this will most likely output more information than you actually want. You may want to look at qa1370 for more information.

In general though, I'd recommend you get a hardware USB analyzer, they make this sort of thing much easier.