[Discuss-gnuradio] Re: synchronizing sound cards in a cluster (fwd)

[Eugen Leitl]

---------- Forwarded message ----------
Date: Thu, 13 Mar 2003 15:18:37 -0800
From: Michael Stein <address@hidden>
To: Jim Lux <address@hidden>
Cc: alvin <address@hidden>, address@hidden
Subject: Re: synchronizing sound cards in a cluster

two ideas:

a. injection lock the crystal oscillator on the soundcard (assuming
   it has a separate crystal for sampling/ADC processing).  If all sound
   cards in the cluster are the same model/version then they could all be
   run/locked from one source.  This might be as simple as an external
   clock signal feed via a series resistor/capacitor to one pin of the
   existing crystal on the sound card.

b. Use multichannel sound cards and put a timing signal on one
   channel.  Assuming the sampling on each card is driven by the same
   clock (likely if all one chip) then I'd think it would then be
   possible to align the data from multiple sound cards in software
   using the timing channel from each card.

   This does not assume that the cards sample each channel at the same
   time, just that there is a consistant pattern in the how a card
   samples it's multiple channels.  It does "waste" some channels.
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