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Re: [Discuss-gnuradio] Still not working with 2 DBSRX... :(

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] Still not working with 2 DBSRX... :(
Date: Wed, 24 Oct 2007 12:16:53 -0700
User-agent: Mutt/1.5.9i

On Wed, Oct 24, 2007 at 02:29:31PM -0400, Jared Jensen wrote:

> Wow.  I'm still not able to get data out of my 2nd DBSRX.  I have
> verified the board is good.  I modified multi-antenna/multi-fft.py
> to use 2 DBSRX board and the 2rx 2tx fpga build.  It works, and I
> can point the boards at different frequencies and see good data.  So
> I know the hardware is working.  Ergo, the problem is with my code,
> and I'm not sure what to do next.  I've debugged this ad nauseum.
> I've verified that I setup r, n, gc1, gc2... all correctly.  I
> rebuilt usrp_standard.cc with debugging info as well as
> db_dbs_rx.py.  My code does the same things in setup.  I think I'm
> setting up each dbsrx correctly.  They return success on tune, and
> return successfully from all of the write_i2c commands.  I'm using
> I2C_ADDR 0x67 for subdev A, and I2C_ADDR 0x65 for subdev B.  I've
> changed those randomly and found that it correctly fails.  So I'm
> fairly confident that the commands are getting down to the DBSRXs.

> When I call 
> usrp_standard_rx::make(0, decim=64, nchannels=2, mux=0x32103210, 
> fpga_mode=0x00, fusb_block_size=0, fusb_nblocks=0, "std_2rxhb_2tx.rbf", 
> "std.ihx") 
> it returns a valid usrp device, and when I query the number of channels, it 
> says 2.  But when I do a 
> dev->start();  followed by
> nRead = dev->read(arr, buf_size, &bOverrun); and
> fwrite(arr,1,nRead, USRPfid);
> I get perfect data for channel 0 (RXA) , but channel 1 (RXB) is just the 
> noise floor.  Loading it into Matlab and looking at the fft shows RXA is 
> doing perfectly, while RXB has no signal magnitude.  (This is when I point it 
> at two known frequencies where both are looking at signals with good power... 
> and even when I point them at the same frequency.)  Using ASCII art...
> FFT_RXA is like....
>        |||||
>      |||||||
> __|||||||||___
> and FFT_RXB is just....
> _____________.

> I'm brainstorming and I wonder if I setup RXB correctly, but haven't
> sent some command to gate the data through.  Or if there is an
> additional step when using 2 channels that isn't documented.  Any
> ideas of things I could look at?

No magic that isn't contained in db_dbs_rx.py

Can your code, in single channel mode, properly talk to the DBSRX on
the B side?  Do you get good data from it?  Be sure to remove the
DBSRX on the A side just to be sure that you're really talking to the
B side ;)

If not, I suspect that there is some usage of "self._which" in the python
code that you haven't properly mapped to your C++ code.


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