Is there a way to use a computer's USB port as a PWM controller? I think I know how an analog audio port might be used; I could use a tone generator to send a variable duty cycle square wave at, say, 5kHz to a comparator driving a MOSFET. Power would have to come from a wall wart or the USB port. But I'm thinking the 5v power of the USB port could drive a logic MOSFET directly, and thereby give a nice simple PWM controller for cheap. Now, I already have a LabJack which is a USB powered data acquisition device. It's perfectly capable of performing the PWM function. But it's ~$115, and I'm wondering if there is a solution that might be <$5. I think it's "just" a software problem, but maybe someone here knows more about USB?