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


From: George Nychis
Subject: Re: [Discuss-gnuradio] help with tuning RFX2400 MIMO_b, weird RX results
Date: Tue, 29 Apr 2008 14:08:45 -0400
User-agent: Thunderbird 2.0.0.12 (X11/20080227)

So, I am finally able to decode something after setting the correct RX mux... I suppose it was incorrect for this daughterboard.

Does the RX2 port need to be enabled for the RX/TX port on the card to receive properly?

If I setup the RX as follows......
d_rx->_write_oe(d_side,POWER_UP|RX2_RX1N|ENABLE,0xffff);
d_rx->write_io(d_side,(~POWER_UP)|RX2_RX1N|ENABLE,POWER_UP|RX2_RX1N|ENABLE);
d_rx->write_io(d_side,0,RX2_RX1N);
d_tx->write_io(d_side,~RX_TXN,RX_TXN);

...what I receive looks like this:
http://cyprus.cmcl.cs.cmu.edu/tmp/flex_graphs/flex_rx2dis.jpg

If I enable RX port 2 also, such that I only add this line....
d_rx->write_io(d_side,RX2_RX1N,RX2_RX1N);

... what I receive looks like this:
http://cyprus.cmcl.cs.cmu.edu/tmp/flex_graphs/flex_rx2en.jpg

... and I am now able to get pretty accurate decoding.

But, I was simply wondering if someone can provide insight in to why this is. Does RX2 need to be enabled?

Thanks,
George


Long, Jeffrey P. wrote:
Yeah, looks better but still some offset on the I rail. The wideness of
the ring could be ISI(whats your BT?) in concert with carrier mismatch
spin if you are using two boards. The only reason I say this is that
the width does not look to be very noise like. Just a guess of course.
:)

-Jeff

-----Original Message-----
From: George Nychis [mailto:address@hidden Sent: Tuesday, April 29, 2008 11:10 AM
To: Long, Jeffrey P.
Cc: Eric Blossom; address@hidden
Subject: Re: [Discuss-gnuradio] help with tuning RFX2400 MIMO_b,weird
RX results

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


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