2006-11-28 11:01:29

by Olivier Le Pogam

[permalink] [raw]
Subject: Re: [Bluez-devel] Master / Slave question

Hi Peter,

Many many many thanks for your answer, I was supposing
a low level issue indeed !

I am actually using a generic Bluetooth key, the kind of
ones you can plug everywhere and which are recognised
by Microsoft Drivers. It is a HCI type 1 (Bluetooth 1.1).

So basically ... only 1 slave connection at a time for
each bluetooth adaptor ? How many bluetooth adaptors
do you think I can deal with under BlueZ in the case I
definetely want to be able to deal with concurrent incoming
connections ?

Even if I buy bluetooth 2.0 adaptors, I suppose the problem
will be the same, assuming my mobile phones are anyway
always on a lower bluetooth version ?

Many thanks again,
Oli

----- Original Message -----
From: "Peter Wippich" <[email protected]>
To: "Olivier Le Pogam" <[email protected]>; "BlueZ development"
<[email protected]>
Sent: Tuesday, November 28, 2006 11:24 AM
Subject: Re: [Bluez-devel] Master / Slave question


>
> Hi Olivier,
>
>>> lots of stuff deleted.....
>
> your problem is hardware / general Bluetooth / LM related.
>
> Earlier BT implementations (and may be even actual) support only one slave
> connection at a time. This is why the master slave switch was introduced !
> (I think with BT 1.0B).
> Newer implementations MAY support up to two slave connections or at least
> one Master and one Slave connection.
>
> What hardware are you using ?
>
> Ciao,
>
> Peter
>
>
>
> | Peter Wippich Voice: +49 30 46776411 |
> | G&W Instruments GmbH fax: +49 30 46776419 |
> | Gustav-Meyer-Allee 25, Geb. 12 Email: [email protected] |
> | D-13355 Berlin / Germany |
>
>
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.409 / Virus Database: 268.14.19/555 - Release Date:
> 27/11/2006
>
>



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2006-11-30 17:12:39

by Andrew Kohlsmith

[permalink] [raw]
Subject: Re: [Bluez-devel] Master / Slave question

On Tuesday 28 November 2006 06:34, Peter Wippich wrote:
> You should try to get a newer BT 2.0 device. If I remember right the newer
> CSR devices support two slaves at a time (at least they support one slave
> and one Master connection simultaniously).

I'm confused; I thought the limitation was with early early BT 1.0B
implementations, but now you're saying that BT2.0 even has this limit? I
can't, for example, have one BT dongle and work with 2, 3, 4 or more devices
at the same time?

> For a server application like yours I would suggest to use the role
> switch feature in a more relaxed way. So, once a connection comes in try
> to do a role switch. If it succeed it is fine and you're able to accept an
> additional connection. If it fails you're out of resources but at least
> can service the current connection.

Interesting. Always try to become a slave (i.e. let the phone be the master
if it'll let you), correct?

Regards,
Andrew

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2006-11-28 11:34:30

by Peter Wippich

[permalink] [raw]
Subject: Re: [Bluez-devel] Master / Slave question


Hi Oli,

> I am actually using a generic Bluetooth key, the kind of
> ones you can plug everywhere and which are recognised
> by Microsoft Drivers. It is a HCI type 1 (Bluetooth 1.1).
You should try to get a newer BT 2.0 device. If I remember right the newer
CSR devices support two slaves at a time (at least they support one slave
and one Master connection simultaniously).

> So basically ... only 1 slave connection at a time for
> each bluetooth adaptor ? How many bluetooth adaptors
> do you think I can deal with under BlueZ in the case I
> definetely want to be able to deal with concurrent incoming
> connections ?
There is no real hard limit for the number of adapters you can use with
BlueZ. Link key managment may become a little bit confusing (on the phone
side) because the Link key is bound to the BT address of the adaptor. So
if a phone connects to, say adaptor 1 the first time and then to adaptor 2
the second time it must pair again 8if your application needs security at
all).

> Even if I buy bluetooth 2.0 adaptors, I suppose the problem
> will be the same, assuming my mobile phones are anyway
> always on a lower bluetooth version ?

I think most phones should, in general, support Master/Slave switch.
However, even when th Bluetooth implementation on the phone supports it,
it is possible that a role switch request is rejected on the profile layer
(depends on implementation).
For a server application like yours I would suggest to use the role
switch feature in a more relaxed way. So, once a connection comes in try
to do a role switch. If it succeed it is fine and you're able to accept an
additional connection. If it fails you're out of resources but at least
can service the current connection.

However, if I understand it right you can not set this behaviour in
hcid.conf. You have to implement it in your application.

Ciao,

Peter



| Peter Wippich Voice: +49 30 46776411 |
| G&W Instruments GmbH fax: +49 30 46776419 |
| Gustav-Meyer-Allee 25, Geb. 12 Email: [email protected] |
| D-13355 Berlin / Germany |


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2006-12-01 13:22:53

by Peter Wippich

[permalink] [raw]
Subject: Re: [Bluez-devel] Master / Slave question


Hi Andrew,

On Thu, 30 Nov 2006, Andrew Kohlsmith wrote:
> On Tuesday 28 November 2006 06:34, Peter Wippich wrote:
> > You should try to get a newer BT 2.0 device. If I remember right the newer
> > CSR devices support two slaves at a time (at least they support one slave
> > and one Master connection simultaniously).
>
> I'm confused; I thought the limitation was with early early BT 1.0B
> implementations, but now you're saying that BT2.0 even has this limit? I
> can't, for example, have one BT dongle and work with 2, 3, 4 or more devices
> at the same time?

I think the confusion was caused by the limitations introduced with the
device roles: master and slave. So most modern devices support the
following:

Master with up to 7 slaves.
Master to (6 ?) slaves and Slave to 1 Master.
Slave to 2 Masters.

> > For a server application like yours I would suggest to use the role
> > switch feature in a more relaxed way. So, once a connection comes in try
> > to do a role switch. If it succeed it is fine and you're able to accept an
> > additional connection. If it fails you're out of resources but at least
> > can service the current connection.
>
> Interesting. Always try to become a slave (i.e. let the phone be the master
> if it'll let you), correct?
No, the other way round. Always try to become a master to be able to
service additional connections and let the phone be the slave. See above
for the reason.

Ciao,

Peter



| Peter Wippich Voice: +49 30 46776411 |
| G&W Instruments GmbH fax: +49 30 46776419 |
| Gustav-Meyer-Allee 25, Geb. 12 Email: [email protected] |
| D-13355 Berlin / Germany |


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