Re: [Discuss-gnuradio] Support for 8-bit USB samples in GRC

[Josh Blum]

According to this:
http://gnuradio.org/trac/browser/gnuradio/trunk/gr-usrp/apps/usrp_rx_cfile.cc#L87

if you dont like half band filters or you want to decimate by 4, 
"std_4rx_0tx.rbf" is the firmware for you

-------->

so, it seems that the correct thing to do in grc would be to set this 
special firmware if your desired decim is 4 and its a usrp source.

Does that make sense (to someone in the know)?

-Josh

Marcus D. Leech wrote:
> Marcus D. Leech wrote:
> > Josh Blum wrote:
> >   
> > > svn up!
> > >
> > > let me know if something goes wrong
> > >
> > >     
> > Intersesting.
> >
> > When I use 8-bit samples with decim=8 or higher, things are peachy.
> >
> > But when I use decim=16 with 8-bits samples, I get a continuous stream
> > of -423dB out of the FFT Log Power sink.
> >
> > I think what I'm getting is a pile of 0s from the USRP when decim=4.
> >
> > Can anybody confirm that decim < 8 actually works on the USRP?
> >
> >
> >
> >   
> OK, let's try that again with my brain actually engaged.
>
> Anything with decim=8 or higher, in 8-bit mode, produces "sensible" samples.
>
> Anything with decim lower than 8 (like 4) produces nonsensical results
> in the Log Power FFT sink (a continuous block
>   of -423dB).  I suspect that with decim=4, there ain't nothing but
> zeros going across the USB.
>
> So, does decim=4 actually work on the USRP, or do I need different firmware?