"John" wrote in message ...

Does anyone have experience and/or recommendations
for analogue and digital I/O interfaces based on the Universal
Serial Bus (USB)?

I can't give any specific advice about the USB interface, but I recall
that
there was a PC based spectrum analyser published in QEX within the last
couple of years.

The state of USB has improved pretty dramatically in the past couple of
years. The QEX article was a groundbreaker at the time, but the technology
has moved on.

Presumably you are aware that a USB interface implies computation on both
sides. The relatively recent USB PICs (18F2550, 4550, etc.) incorporate
everything needed for the USB interface except the connector. Only a couple
of years ago a USB controller chip was $26 and it needed a host of
additional parts to actually implement the interface. A smaller USB PIC
costs less than $5 and includes *everything*.

Go to http://ww1.microchip.com/downloads/e...Doc/39632D.pdf and take a
look at the capabilities. To see it in an actual circuit, try
http://www.microchip.com/stellent/id...ame =en529760
and download the users guide. The 2550 is the little TQFP to the right of
the board picture, although it is available in a variety of packages, some
more hobbyist-friendly then the tiny one on the board. The only additional
part is an inductor to filter the USB voltage when it is used to power the
target circuit.

This series of parts also includes A/D channels, tho they might not be the
speed and resolution you want. The particular board is a nice one for
experimenting because it includes one of the fast 16-bit parts that are
easily programmable in a high level language, along with the USB interface.

...