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Re: [Discuss-gnuradio] 8-bit samples on USRP2 at 33.333Msps
From: |
Josh Blum |
Subject: |
Re: [Discuss-gnuradio] 8-bit samples on USRP2 at 33.333Msps |
Date: |
Wed, 09 Nov 2011 19:36:40 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1 |
On 11/09/2011 07:07 PM, Marcus D. Leech wrote:
> Just did a quick test of 8-bit samples on a USRP2, on one of my 6-core
> AMD machines.
>
> I can get to 33Msps with a fairly simple SOURCE-->MULT-->FFT_SINK
> flow-graph, but anything more complicated causes overruns.
>
> If I try 50Msps, I get near-continuous overruns.
>
> This is on an AMD Phenom II X6-1055 -- the cores run at 2.8GHz, and I
> have 4GB of 1333MHz memory.
>
> It's a fairly-wimpy machine as multi-core DSP monsters go, but I thought
> I'd give it a try.
>
My AMD Athlon(tm) II X4 620 Processor does jyst fine with 50Msps FFT
plotter. Just sayin :-)
> People should be aware that since this uses the upper-half (as far as I
> know) of the ADC, you'll need more gain to drive those
> 8 bits.
There is a configurable scale factor (see the stream args in the grc
block). It defaults to a value that gives you the upper 8.
-Josh