Re: [Discuss-gnuradio] Modem and/or ADSL Daughter card

[David Young]

On Wed, May 10, 2006 at 07:24:07PM -0700, Eric Blossom wrote:
> On Thu, May 04, 2006 at 02:01:31PM -0400, Michael Milner wrote:
> > Hello,
> > 
> > I was just wondering if anyone has used GNURadio for any non-radio
> > applications, specifically phone line modulation/demodulation.
> > 
> > It shouldn't be too difficult to design a daughter board for the USRP to
> > sample phone line voltage (with an appropriate line interface circuit of
> > course).  After that it should be rather easy in GNURadio to generate DTMF
> > tones for dialing, and modem tones for data communication.
> > 
> > Any thoughts?
> > Mike
> 
> A simple DAA (Data Access Arrangement) plus the LF daughterboard would
> probably work.  There are two chip DAA's available.  Been a while
> since I looked, but I think that Crystal Semiconductor used to make
> them.  Google "solid state daa" There's also the classic Midcom
> transformer plus a couple of other discretes.  These things are tricky
> to get right.  You definitely want to find somebody's reference design
> and use that.  Or use the pre-approved chipset.
> 
> The USRP is pretty much thermonuclear overkill for this application.
> You could just use a sound card with a DAA.  That's how all the
> "soft-modems" work.  IIRC some of the the AC97 codecs support a second
> channel for telecom (modem) apps.

Here is an example that uses a sound card, <http://www.araneus.fi/audsl/>.

<idle-musing>
It would be neat if there were the PC audio-out equivalents of the
iGo iTips power adapter plugs, with plugs that adapt audio-out to
media such as AC powerline, phone wire, Cat5, and television cable.
A suitable software modem would adapt to whatever medium was on hand,
adding a new dimension to "ad hoc networking."
</idle-musing>

Dave

-- 
David Young             OJC Technologies
address@hidden      Urbana, IL * (217) 278-3933