Re: [Discuss-gnuradio] USB2 <-> fast ADC & DAC

[Andy Green]

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On Tuesday 27 May 2003 16:58, Paul A. Scott wrote:
> > it was possible to transfer 20MBytes/sec like this with latencies
> > of under 2mS over USB2.  It is this transfer rate which is the
> > limiting factor, not the conversion rates on the ADC or DACs.

Hi Paul -

> Why not use 400MB/sec IEEE 1394 (Firewire) instead?

Here is the reasoning:

 - Firewire is less common than USB2, which is present on all new 
motherboards

 - While not wishing to be a troll, Firewire seems to be headed in the 
opposite direction in terms of port availability

 - Firewire is 400Mbits/sec, USB2 is nominally 480Mbits/sec.   So 
there is no advantage in wire speed to use Firewire.  We found a 
simple blocking IO setup delivered the ~20MBytes/sec performance I 
mentioned, with <2mS latencies.  So this is what we take as our 
deliverable performance.

 - Firewire device chips are less available and more expensive

These considerations make us settle on USB2.

- -Andy
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