Thanks, I'll try it without isolation and see how it works.

> Marc,
>
> Opto isolating USB is generally not normally practiced. I think this
> is because the highish speeds (full speed) and the bi-directional
> comms make it difficult. Opto-isolating high speed USB is not
> practiacl, although there are alternative isolators that will handle
> the speed USB is designed to be used over short distances (and
> generally light-duty equipment) anyway, so earth currents are not much
> of a problem. (Mostly)..
>
> My recommendation would be not to attempt it unless there was a real
> need. If there is a real need, can you isolate at another point
> instead? - e.g an SPI bus is a lot easier to isolate as it is
> uni-directional. . Same with RS232..
>
> If you do have a problem with an earth loop, try placing a low
> resistance (heavy duty) bond wire between the earths of the equipment
> concerned. Most of the current will flow through the bond wire and
> less through your USB earth.
>
> Just my 2c
>
> RP


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