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Author Topic: USB to Serial Adapters  (Read 99814 times)

Gian P. Portanova

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Re: USB to Serial Adapters
« Reply #10 on: December 10, 2004, 01:50:27 pm »

Anybody sending USB up or down a snake between FOH and stage?
How?
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Andy Peters

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Re: USB to Serial Adapters
« Reply #11 on: December 10, 2004, 02:21:26 pm »

Gian wrote on Fri, 10 December 2004 11:50

Anybody sending USB up or down a snake between FOH and stage?
How?


NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO.  Can't be done.

Some reasons, all relating to the USB spec:

1) First and foremost, the USB spec has a distance limit given as a cable delay of 26 ns, which ends up being 5 meters.  If this cable length is exceeded, you will see packets colliding or bus contention as the drivers on both sides of the bus are enabled at the same time.

2) USB cables are specified to be a tight 90-ohm differential impedance; audio snake impedances are rarely specified at all.  The impedance spec helps ensure good signal integrity.  Remember that the bandwidth full-speed USB at 12 Mbps exceeds that of baseband video, and you don't send video down a snake, right?

3) USB also sends power down the cable so you'd need four wires in your snake line.  The spec also details acceptable voltage drops in the cable; a long audio snake may have significant voltage drop and so VBUS may be out of spec at the far end.

There are various gizmos that purport to translate USB to "something else" (Wireless, CAT-5 cable, whatever) but those devices may have severe limitations.  For example, the so-called "Wireless USB" is good for only low-speed devices (keyboards, mice, that sort of thing).  And the USB-over-CAT5 things use specialized transceivers and depend on high-quality cable, which is why CAT5 is specified.  You don't send Ethernet down a snake, right?

--a
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KeithBroughton

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Re: USB to Serial Adapters
« Reply #12 on: December 19, 2004, 02:16:44 pm »

The GUC232A is just fine.
Works so well, I bought 2.
As far as running USB along a snake...no way!
Try setting up the wireless serial  Bluetooth system as indicated on this link...works GREAT!
http://www.driverack.com/drug/view_thread.asp?forumid=12& ;thread_id=38790
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I don't care enough to be apathetic.....

DanLynch

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Re: USB to Serial Adapters
« Reply #13 on: January 08, 2005, 12:00:11 pm »

We deal with this literally every day.  No matter what anyone tells you, there is NO SUCH THING as "the right" USB to serial adaptor.

Adapter A will work great with a Soundweb but not with an Extron switcher.  Then on a different computer, it won't work with either.  Adapter B will work perfectly with every product as long as you don't have an IBM laptop.  Adapter C will be fantastic on the IBM as well as a Toshiba and a Dell, but it will fall on its face as soon as you use an HP laptop.

If you're getting ready to try USB to serial, do one of two things.

1: Forget it!  Order an ethernet-to-serial adaptor from Moxa.com

2: In the real world of limited budgets, go to the local CircuitCity/CompUSA/whatever and buy one of each brand they have available.  After you figure out which one works for your combination of laptop/gear, return the rest.

If anyone tells you that the Blahblahwoof XL254 is the perfect USB-serial adapter, they're more likely to be wrong than right unless you're both using the exact same laptop with the exact same gear.  Buy a bunch of adaptors and try them all until you find the one that works for you.

Dan
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ProSoundWeb Community

Re: USB to Serial Adapters
« Reply #13 on: January 08, 2005, 12:00:11 pm »


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