DComTalk.com

I've been experimenting with one of these
<http://www.dse.co.nz/cgi-bin/dse.storefront/439e0c5f0b45a650273fc0a87f99
06f5/Product/View/XH1142>, with a view to using it in an application for
a client.

I was able to get documentation for the AT commands for the Intel MD566x
chipset from several sources, e.g.
<http://www.dse.co.nz/isroot/dse/support/MD566xAT.PDF>. The various
versions of the document refer to an "IS-101 Voice Application Note",
which I can't seem to find anywhere. Not sure if it's important or not.

To start with, I've been trying to use the speaker and microphone
connectors to get analog audio in and out of the thing. I tell it
"at+fclass=8" to enable voice mode, then "at+vls=7" to go off-hook and
turn on the speaker and microphone, and "at+vts={5,10},{5,10},{5,10}
....etc" to dial a number. I can hear incoming audio just fine, but I
can't seem to send any audio through the microphone connector.

I've tried various other at+vls values, e.g. "at+vls=13", which is
supposed to enable the external speaker and microphone, as opposed to
the internal ones with "at+vls=7". The document says it is "implemented
as 7" anyway, yet the modem returns "ERROR" when I try this command.

Has anyone else had any experience with this modem or chipset? I haven't
experimented with recording or playing back digitized audio yet. Maybe
I'll try that next.

I haven't experimented with recording or playing back digitized audio yet.

I have now, and both recording and playback do work. One thing though:
the description of the AT+VSM command says that "LIN1" audio encoding
uses "twos-complement signed numbers". This is a lie. The numbers are in
fact excess-128 unsigned.

Still can't get any joy out of the microphone input.