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M. Adam Davis wrote:
> Idea:
> 
> Take one oscilloscope probe, and one USB cable. Cut the BNC connector
> off the oscilloscope probe, and the USB B connector off the USB jack
> and splice them together.
> 
> Mount all the USB <--> analog circuitry inside the scope probe body
> and/or the USB A connector body. It would essentially compete with all
> the other USB oscilloscopes out there, but it would be in a single
> cable design - no extra boxes, etc.
> 
>    1. Is this a product you would like?

Definately.

>    2. What are your minimum specifications for this type of product?

At least 50MSps for the work I'm currently doing with a realtime trace
and half decent triggering. Comfortable in the hand!

>    3. What are your ideal specifications for this type of product?

200MSps would be pushing it, no?

>    4. Would this be any more useful or desirable than the current USB
> oscilloscopes available?

Yes. Low power and less desk clutter is never a bad thing.

> My biggest concerns are:
> 
>     * Obtaining the speed necessary to be reasonably useful without
> requiring a lot of components
>     * Synchronizing multiple probes into the computer (Getting nS
> accuracy without wiring the probes together seems problematic...)
>     * Fitting it all into the form factor and power limitations of a
> USB port (ideally 100mA unpowered hub ~0.5W)
>     * Keeping the assembled cost low
> 
> I'd appreciate feedback on any or all of the above (what you want vs
> how to implement it). Ideally it'd be completely open source, but
> using very tiny surface mount parts it might not be easily assembled
> by hand.
> 
> -Adam
> 
> ---
> http://chiphacker.com/ - EE Q&A site

I have definitely thought about that idea a few times. The main problem I
found was being able to isolate the USB power from the signals in a small
and cheap way.

The next fun part is choosing an MCU with good enough raw data->USB
throughput for any kind of decent sample rate. The more you actually
delve deep into the delays associated with getting that data into the PC,
the more a small FPGA (Actel IGLOO, etc) and USB2.0 PHY seem desirable.

Anyway, if your design gets further than just initial scribblings you
deserve a pat on the back.

- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan {a} brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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