2006-07-19 22:28:46

by David Geiger

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Subject: [Bluez-users] CSR BlueCore4 dongles

Hi everybody,

I was just doing an internet search on USB bluetooth dongles and would be
happy to get some feed-back on the results.

My requirements were:
- CSR BlueCore4 (as I have heard it is best supported with btsco)
- Class1
Are there any other important criteria?

The only devices I have found are:
- Level One MDU-0025USB (A2DP, USB 1.1)
- B-Speech Data speed (A2DP)
- Cellink BTA-6030 (USB 2.0)
- EPoX BT-DG07A+ (A2DP?)
- Bluetake BT007EX (A2DP, USB 1.1)

Any experiences with one of the devices or additions are welcome! :)

There are a few questions left, maybe someone can help me here:
- Does the dongle explicitely have to support A2DP?
- What is an "AV profile"? Almost all websites list the "Advanced Audio
Distribution Profile" as an AV profile and say Windows only. Does that mean
it doesn't support A2DP on linux?
E.g.
http://www.b-speech.de/en/produkt-information/stereo-headsets-und-adapter/b-speech_data-speed/
- Does it make sense to buy a dongle with USB 2.0 support? The USB 1.1
datarate is already 12mbit/s which should be enough by far.

Best regards,
David
--
David Geiger
[email protected]

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2006-07-20 16:17:46

by Brad Midgley

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Subject: Re: [Bluez-users] CSR BlueCore4 dongles

Wolfgang

>>>the bus has to fall back to usb1 speeds when a usb1 device
>>>on the bus is active.

> The truth is: every USB device needs time to make their transfers.
> Slow devices need more time than fast. The host is switching between
> slow, fast and high speed devices dynamicly.

Sure... I didn't mean to imply that usb2-to-usb2 transfers would start
using usb1 speeds, only that the usb1 device keeps the bus busier than
you might expect. By active I meant transferring data.

All bets are off when data starts getting constricted. My usb2 burner
would choke while burning sometimes if I used a usb mouse on the same bus.

Brad

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2006-07-20 15:52:47

by Wolfgang Mües

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Subject: Re: [Bluez-users] CSR BlueCore4 dongles

On Thursday 20 July 2006 09:04, Per Thomas Jahr wrote:
> On Wed, 2006-07-19 at 17:47 -0600, Brad Midgley wrote:
> > the bus has to fall back to usb1 speeds when a usb1 device
> > on the bus is active.
>
> That was really useful information!

And a really wrong information....

The truth is: every USB device needs time to make their transfers.
Slow devices need more time than fast. The host is switching between
slow, fast and high speed devices dynamicly.

So a slow device can "steal" much of the available transfer time of the
bus, and slow down fast devices on the same bus. But a slow device can
not urge the host to serve a high speed device with a lower speed.

regards
Wolfgang
--
We're back to the times when men were men
and wrote their own device drivers.

(Linus Torvalds)

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2006-07-20 07:04:35

by Per Thomas Jahr

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Subject: Re: [Bluez-users] CSR BlueCore4 dongles

On Wed, 2006-07-19 at 17:47 -0600, Brad Midgley wrote:
> the bus has to fall back to usb1 speeds when a usb1 device
> on the bus is active.

That was really useful information! I have always wondered where the
usb2 speed had gone on my system. Thanks!

--
Per Thomas


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2006-07-19 23:47:56

by Brad Midgley

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Subject: Re: [Bluez-users] CSR BlueCore4 dongles

David

> I was just doing an internet search on USB bluetooth dongles and would be
> happy to get some feed-back on the results.
>
> My requirements were:
> - CSR BlueCore4 (as I have heard it is best supported with btsco)
> - Class1
> Are there any other important criteria?
>
> The only devices I have found are:
> - Level One MDU-0025USB (A2DP, USB 1.1)
> - B-Speech Data speed (A2DP)
> - Cellink BTA-6030 (USB 2.0)
> - EPoX BT-DG07A+ (A2DP?)
> - Bluetake BT007EX (A2DP, USB 1.1)
>
> Any experiences with one of the devices or additions are welcome! :)

the bt007ex is a nice adapter. it's also just about the only one that is
easy to find in the US but that doesn't necessarily mean you'll find it
in Germany. fwiw, it includes a2dp drivers for xp that we've used for
testing interoperation (the w2k driver wouldn't work for me)

> There are a few questions left, maybe someone can help me here:
> - Does the dongle explicitely have to support A2DP?

when a dongle is advertised to support a2dp, it either means that you
can add a driver that provides a2dp or that such a driver is included
for windows. every dongle should support a2dp as long as it's not
seriously broken, so it really doesn't mean anything.

> - What is an "AV profile"? Almost all websites list the "Advanced Audio
> Distribution Profile" as an AV profile and say Windows only. Does that mean
> it doesn't support A2DP on linux?

this only relates to windows drivers. you can drive a2dp from linux
(such as we have it)

> http://www.b-speech.de/en/produkt-information/stereo-headsets-und-adapter/b-speech_data-speed/
> - Does it make sense to buy a dongle with USB 2.0 support? The USB 1.1
> datarate is already 12mbit/s which should be enough by far.

the only real reason for usb2 is coexistence with other usb2 devices on
the same bus. the bus has to fall back to usb1 speeds when a usb1 device
on the bus is active.

brad

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