Building a VOIP Device

Discussion in 'Embedded Systems and Microcontrollers' started by gmcmurry, Mar 30, 2010.

  1. gmcmurry

    Thread Starter Member

    Mar 29, 2010
    Can anyone get me started reading about how to connect a micro to a phone line so that it can do things like VOIP / DIAL / ETC...?

    I have designed modems before but never anything that could digitize audio and connect it to a "plain old telephone service" POTS.

    I am looking for chip sets, research material, primers, anything that can get me started.

  2. beenthere

    Retired Moderator

    Apr 20, 2004
    VOIP is done over a somewhat fast internet connection, like cable or DSL. You should realize from your experience -
    - that audio is just what the POTS system is designed for. The internet protocol uses packets of data.

    In the case of digitizing voice, an A to D converter does the digitizing. That's the easy part. Arranging for a connection by TCP/IP and sending/receiving packets of voice data is a bit busy. You might find that a computer's sound card can play a role.

    I would wonder if a "micro" - possibly a microcomputer? - has the horsepower to handle TCP/IP and the digitizing all at once.
  3. BMorse

    AAC Fanatic!

    Sep 26, 2009
  4. n9352527

    AAC Fanatic!

    Oct 14, 2005
    Have a read on this AD Blackfin VOIP article to get a short overview of what is involved in VOIP.

    VOIP can be considered the opposite of modem, where analogue voice signal is transferred through digital TCP/IP connection. Whereas in modem, digital data is transferred through analogue PSTN line.

    So, in VOIP there is no POTS line involved, unless you want to connect standard phone devices or POTS line at the ends (phone, inter-connection with PABX, old phone system, etc.). You will need FXS or FXO port to do these.

    You need to consider the session control and the codec that you are going to use. For example SIP or H.323 and Speex or G.7xx. I strongly suggest going with a reference design at first, for example the Blackfin BRAVO VOIP. This will minimise the work that you need to do to get a prototype running.
  5. rjenkins

    AAC Fanatic!

    Nov 6, 2005