Re: [Discuss-gnuradio] help with tuning RFX2400 MIMO_b, weird RX results

[George Nychis]

OK, this is my last cry for help...  I'm hoping you have an idea of what 
I'm tuning wrong, Matt.

I have added print statements for every single _write_fpga_reg, pga_set, 
 _write_spi, _write_io, _write_oe, etc.... and I compare the function 
calls by a standard python RFX2400 MIMO_b tune with my C++ tuning code.

Everything that I see is mimicked exactly... but that doesn't 
necessarily mean I see everything ;)

The only thing that doesn't match up, that I cannot understand, is that 
when I call d_rx->set_rx/tx_freq(0, -4e6)  (which is what the python 
code does) ... everything goes down hill.  After calling set_tx_freq() 
my transmitter breaks (which works otherwise).

After calling set_rx_freq(), my receiver becomes even more broken and my 
incoming signal looks like this:
http://cyprus.cmcl.cs.cmu.edu/tmp/new_flex/set_rx_freq.jpg

If I do not call set_rx_freq(), my incoming signal looks like this:
http://cyprus.cmcl.cs.cmu.edu/tmp/new_flex/no_set_rx_freq.jpg

I've dug into these function calls and the values are set the same in 
both cases.

If I enable RX2, I see this on my RX/TX:
http://cyprus.cmcl.cs.cmu.edu/tmp/new_flex/gmsk_ivq_flex.jpg

Using a python tuned board, I see this:
http://cyprus.cmcl.cs.cmu.edu/tmp/new_flex/gmsk_ivq_regular.jpg

Major difference.

I'd sincerely appreciate any feedback.

Thanks!
George


George Nychis wrote:
> Hi Bob!
>
> Right, when I side "wide circle", i didn't mean flat, i meant that the 
> circle seemed thick... as if there is a large variation in amplitude.
>
> my newest graph seems a little better:
> http://cyprus.cmcl.cs.cmu.edu/tmp/flex_graphs/flex_rx2en.jpg
>
> Thanks,
> George
>
>
> Bob McGwier wrote:
> > George:
> >
> > The flattened ellipsoid is in the eye of the beholder.  ;-).  It isn't 
> > really.  It is the aspect ratio of your gnuplot.  You are clipped and 
> > it appears there is a slight DC bias on the I channel to plus DC 
> > (pushed slightly to the right).
> >
> > Bob
> >
> >
> > George Nychis wrote:
> > > I'm getting a little closer...
> > > http://cyprus.cmcl.cs.cmu.edu/tmp/flex_graphs/closer.jpg
> > >
> > > it looks like I'm clipping a little bit, and is that "wide circle" 
> > > effect a result of DC offset?
> > >
> > > - George
> > >
> > >
> > > Long, Jeffrey P. wrote:
> > > > Kind of looks like it is clipping to me and possibly some DC offset
> > > > problems.
> > > > -Jeff
> > > > -----Original Message-----
> > > > From: address@hidden
> > > > [mailto:address@hidden On Behalf Of
> > > > George Nychis
> > > > Sent: Tuesday, April 29, 2008 10:13 AM
> > > > To: Eric Blossom
> > > > Cc: address@hidden
> > > > Subject: Re: [Discuss-gnuradio] help with tuning RFX2400 MIMO_b,weird
> > > > RX results
> > > >
> > > >
> > > > > You're not being shunned :)
> > > > >
> > > > > Stating the obvious, it would be great to have 1 complete
> > > > > implementation of the C++ daughterboard code, rather than N partial
> > > > > implementations.
> > > >
> > > > Hopefully once I get passed my May madness I can work with Michael 
> > > > on  this.
> > > >
> > > > Does it look like I am clipping? I am not changing the transmitter  
> > > > between the two dumps. I figured the rx gain was too high but it seems
> > > >
> > > > to be being set correctly.
> > > >
> > > > - George
> > > >
> > > >
> > > > _______________________________________________
> > > > Discuss-gnuradio mailing list
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> > > > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> > >
> > >
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