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Date:      Mon, 10 Feb 97  0:27:45 +0000
From:      Andrew.Gordon@net-tel.co.uk
To:        smp@csn.net
Cc:        hardware@FreeBSD.ORG, multimedia@FreeBSD.ORG
Subject:   Re(2): isdn cards
Message-ID:  <"be7-970210002711-4D07*/G=Andrew/S=Gordon/O=NET-TEL Computer Systems Ltd/PRMD=NET-TEL/ADMD=Gold 400/C=GB/"@MHS>
In-Reply-To: <199702092254.PAA27689@clem.systemsix.com>

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> I previously said:
> > I know there are currently no drivers available for North American ISDN
> > systems, but several people have proposed working on such a beast.
> >I have a chance to pick up a couple cheaply and am wondering whether
> 
> I have just been kicking around the idea of using the motorola isdn
> bitsurfr pro ISA (ie, the internal card as oppossed to the external
> device) as one would the external device.  Specifically the box says
> is uses an internal 16550 with the standard AT command set.  So given
> that I have already setup a PPP connection on FreeBSD with kernel PPP
> and an external bitsurfr, wouldn't it also be possible to do the same
> with the ISA card version (although I suspect I would have no access to
> the fancy SOHO features till a true driver was written)?
> Has anyone tried this?

Are you sure that the internal bitsurfr is actually any different to
the external (in the sense that an internal modem is no different
to an external one).  On the one hand, if it really does emulate
a 16550 faithfully, it will work straight away but give you all 
the limitations of an external TA; on the other hand, if it doesn't
you will be straight into writing a device driver for undocumented
hardware before you even get started.

Looking at:
http://www.mot.com/MIMS/ISG/Products/bitsurfr_pc/app-notes.html
it suggests you are right about the 16550 - though it's PnP with
the associated inconvenience - but gives no hint that it can do
any more than be an external TA, emphasising its "modem like"
character.  Doing PPP this way (ie. encode once as async PPP then
decode/re-encode as sync PPP in the TA) will inevitably give some
additional latency compared to driving a real piece of hardware
more directly.

So, IMHO, if you want a quick getaway stick with the external TA
(avoiding the PnP aggro), but if you are talking of a real development
project, why not leverage the work that has been done for Euro-ISDN
and go for one of the cards already supported under FreeBSD by
the BISDN package?  The hardware reverse-engineering has already been done,
so the remaining work is to implement whichever D channel protocol
your teleco has implemented.

The two main cards supported by BISDN are the Teles BRI/16.3 and the
AVM A1.  Teles certainly sell a USA-specific card "BRI/U", which
is just the 16.3 with an on-board NT1 ("U" interface to "S" interface
convertor - with Euro-ISDN, the Teleco provides the NT1).
Details are at the Teles USA web site http://teles.winterlan.net/
(their 'home' site is http://www.teles.de/).  AVM (http://www.avm.de)
also apparently do a USA version of their A1 card, as their web page
offers drivers for it, but I can't find any more details.

The Teles and AVM cards are almost identical, giving you raw access to
the B and D channels (with HDLC being done by the card where needed,
and with deeper FIFOs than a 16550) and so letting you do anything that
the line itself can do (voice calls, two simultaneous calls to different
destinations etc. which are hard to do with an interface that thinks
its a modem).  For more info about the hardware, see http://www.arg1.demon.co.uk/avm.html



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