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: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
George Nychis
Sent: Tuesday, April 29, 2008 10:13 AM
To: Eric Blossom
Cc: discuss-gnuradio@gnu.org
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
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