Re: [Bluez-users] Embedded bluetooth recommendations

[Marcel Holtmann <marcel@holtmann.org>]

Hi Wiebe,

> > > I have a question about embedded Bluetooth. I'm working on a feedback
> > > control project which involves 8 devices. Up till now a module has
> > > been used with integrated stack but this is unable to support an
> > > RFCOMM link with seven slaves and the response time of a scatternet is
> > > unacceptable so I'm now looking for a multiprocessor solution with a
> > > separate stack.
> >
> > are you talking about seven RFCOMM links on the same ACL link or about
> > seven different ACL links. If you really wanna work with piconet where
> > the master controls 7 slaves you should use a CSR chip, because all
> > other Bluetooth chips are acting somekind weird. However even with the
> > CSR stuff you must make sure that at least a HCI 18.2 firmware is used.
> 
> Yes the idea is to use seven ACL links. Luckily the current design uses a
> sharp process in combination with a CSR chip.

I just saw that the HCI 18.3 is already released, but I can't find the
release notes or the changelog for that version.

> > > I'm currently experimenting with a sharp LH79520 with embedded Linux
> > > from metrowerks and Bluez but this seems to be overkill because the
> > > application requirements themselves are minimal (7 way cable
> > > replacement).
> >
> > The Sharp uses an ARM7TDMI. Actually this is really overkill and then
> > you should better buy a Bluetooth chip that itself uses this ARM chip
> > like Zeevo etc. However then the above point comes in ...
> 
> I took a look at the Zeevo but it only seems to support 4 simultaneous ACK
> links which is a bit worrying given that it's based on the same ARM chip.

I think that even CSR might not guarantee you to work with 7 ACL links
at the same time and I only tested these with HID and these devices are
using the sniff mode quite often, because there is not so much data.

> > > Does anyone have a suggestion of a combination of stack, operating
> > > system and microprocessor that is known to work together and has
> > > minimum requirements in terms of RAM, ROM and processor speed (cost)?
> >
> > I am not a microprocessor expert, but actually every processor with
> > Linux support should be useable and BlueZ is of course the best choice
> > for a Bluetooth stack.
> 
> Thanks for the advice. This is the route I'm going to be taking.

Maybe I should put out a page with success stories using BlueZ. Be my
guest to write the first report ;)

Regards

Marcel




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