Re: Switching device types in a USB device

In article <MeedncHnN8cEgKnVnZ2dneKdnZydnZ2d@xxxxxxxxxxxxxx>,
alj@xxxxxxxxxx says...
Paul Carpenter wrote:
In article <ts-dnV9x5ujJVK7VRVnyjgA@xxxxxxxxxxxxxx>, alj@xxxxxxxxxx
says...
A similar technique used by people like Picotech for their scopes.

Enumerate as V1.1 device with next to no endpoints. Will only do anything
after driver initialised to load firmware, and then if possible
reenumerate as USB 2.0 device with LOTS and LOTS of endpoints.
Really ridiculous as Flash memory is not that expensive and would be
easier to upload the code when it changes, and make for easier use!
Having seen USB 2.0 systems wait for the USB V1.1 transfer to complete
the transfer several times, when it gets confused (just today saw
one logging error codes as data so upto -150V data points for device
being monitored that could only produce -12V MAX!

That system needs more recycling for USB drivers than anything else.

Does this happen often?

If yo mean recycling the system to reenumerate because the drivers
are out of sync, for those devices too often for my liking. Whne
developing it can be many times a day. Sometimes pulling lead out and
reenumerating sorts it out but not always.

I meant when using the Picotech stuff. I wouldn't be very happy having
to unplug/plug a commercial product all the time.

I was talking about the Picotech stuff, they are the reason for the re-
enumerations and sonetimes system cycling. I *personally* would not
use them, however I have a customer who loves them.

If it stays in sync (driver and device) it is fine, otherwise it is
just as bad as many inkjet USB printers.

There are other reasons as well why I would not use them, that I will
not discuss here.

--
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