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Re: [Discuss-gnuradio] USRP2 missing Quadrature samples

From: Leslie Choong
Subject: Re: [Discuss-gnuradio] USRP2 missing Quadrature samples
Date: Wed, 4 Feb 2009 17:24:13 -0800

I'm baffled. I formatted the SD card and made sure the USRP2 didn't
boot up (No LEDs lit). Then reflashed it with the latest firmware and
FPGA image (2 LEDs lit). I still see 0.0 Q samples at 2.4G, 2.45G etc.
I've tried swapping the RFX 2400 daughterboard with a spare AND two
with different USRP2's and still see the same behaviour. I've done
this with the latest trunk of GNURadio (revision 10392).

Are the samples I'm seeing at 2.425G even valid? I'm mainly concerned
with the output range of +/- 2mV. Are others seeing this output range
for their USRP2's?

Thanks for reading and all the help!

On Tue, Feb 3, 2009 at 5:25 PM, Michael Ossmann <address@hidden> wrote:
> I have some samples taken at 2.4, 2.44, 2.45, and 2.5 GHz all with a
> USRP and RFX2400 with recently built firmware, fpga, and software.
> Mine don't exhibit the problems you describe at all.  I'm stumped.
> On Tue, Feb 03, 2009 at 04:50:46PM -0800, Leslie Choong wrote:
>> I was able to compile the firmware with Eric's suggestion but it made
>> no difference on the performance. I tested this out on another USRP2
>> to see if it was a hardware issue but again got the same results.
>> I noticed something interesting though: Using a RFX 2400 board if I
>> try to tune to 2.45G (my original freq), 2.4G or 2.5G I get similar
>> behaviour (Q samples are 0). If I tune away from them I start to
>> receive Q samples!
>> I sampled at 2.425G and compared it to the USRP1. I noticed 2 things:
>> 1. The IQ samples at 2.425G seem like complete noise compared to the
>> USRP1 samples.
>> 2. The Amplitude of the USRP2 IQ samples is much lower than the USRP1
>> I have posted these results at: http://www.cs.ucla.edu/~septikus/usrp2.html
>> Am I setting something up wrong? Why are the IQ samples I'm getting
>> just noise? This is using my own compiled firmware and the latest FPGA
>> image off the GNURadio website.
>> Any further help or comments would be great! Thanks again for all your help!
>> -Leslie
>> On Fri, Jan 30, 2009 at 4:41 PM, Eric Blossom <address@hidden> wrote:
>> > On Fri, Jan 30, 2009 at 04:24:55PM -0800, Leslie Choong wrote:
>> >> So I've pulled down the most recent trunk and re-built gnuradio. One
>> >> thing I noticed that I forgot about was that running make in
>> >> gnuradio/usrp2 does not produce a txrx.bin under usrp2/firmware/apps.
>> >> I must have copied the latest one sitting in the trunk which is dated
>> >> Dec 31st (same date as the FPGA binary blob).
>> >>
>> >> I looked into it and it seems like ./configure did not find mb-gcc
>> >> (the microblaze toolchain). I installed the pre-compiled binary from
>> >> instructions here:
>> >> http://gnuradio.org/trac/wiki/USRP2UserFAQ
>> >>
>> >> And then after configuring and running make I get this error:
>> >> make[3]: Entering directory `/home/leslie/gnuradio/usrp2/firmware/lib'
>> >> if gcc -DHAVE_CONFIG_H -I. -I. -I..  -DHAL_IO_USES_UART  -I../include
>> >> -I../lib  --std=gnu99 -Wall -Werror-implicit-function-declaration
>> >> -mxl-soft-div -msoft-float -mxl-soft-mul -mxl-barrel-shift -g -O2 -MT
>> >> abort.o -MD -MP -MF ".deps/abort.Tpo" -c -o abort.o abort.c; \
>> >>       then mv -f ".deps/abort.Tpo" ".deps/abort.Po"; else rm -f
>> >> ".deps/abort.Tpo"; exit 1; fi
>> >> cc1: error: unrecognized command line option "-mxl-soft-div"
>> >> cc1: error: unrecognized command line option "-mxl-soft-mul"
>> >> cc1: error: unrecognized command line option "-mxl-barrel-shift"
>> >> make[3]: *** [abort.o] Error 1
>> >
>> > Run ./configure from top directory.  Otherwise you get gcc instead of 
>> > mb-gcc.
>> >
>> > Eric
>> >

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