How to setup adc_rate in grc_usrp.simple_source_c


#1

Hi All,

i noticed that there will be used in the most example some
special sources. Not the <grc_usrp.simple_source_c> as in my program.

Do i have to use for example <usrp.source_c> to adjust the adc_rate ?
Which one is the better ?
Do i need <grc_usrp.simple_source_c> to visualize it in my Companion ?

Regards Markus


#2

I can not find the class <grc_usrp.simple_source_c>
in the doxygen generated API.
Where to find it ?


#3

Josh B. <josh joshknows.com> writes:

Simple source exists because actual usrp api is sooo crazy. The goal of
the simple source and simple sink is to provide the most useful options
to the usrp user.

Thank you for your Reply.

Is it possible to make an offset so that i get the
right dB not dBFS ?


#4

On Fri, Mar 06, 2009 at 11:59:13AM +0000, feldmaus wrote:

Josh B. <josh joshknows.com> writes:

Simple source exists because actual usrp api is sooo crazy. The goal of
the simple source and simple sink is to provide the most useful options
to the usrp user.

Thank you for your Reply.

Is it possible to make an offset so that i get the
right dB not dBFS ?

Marcus,

To reiterate what other people have said over the past few days,
calibrating the USRP requires an understanding of all of the analog
and digital controls that are in the path, and then computing
calibration coefficients for each possible combination. E.g.,
changing the gain would change the calibration. Changing the ambient
temperature will change the calibration. Changing daughterboard
types will change the calibration, changing daughterboards instances
will change the calibration. Changing the interpolation or decimation
will change the calibration…

Spending some time with the USRP FAQ should allow you to understand
what’s going on. This diagram page, RFX-2400 specific, should help too:
http://gnuradio.org/trac/wiki/UsrpRfxDiagrams

Eric


#5

To see the usrp simple source in doxygen, you will have to generate
doxygen for your gnuradio install (./configure --enable doxygen). The
documentation at gnuradio.org will not have it.

It may help you to look at
http://gnuradio.org/trac/browser/gnuradio/trunk/grc/src/grc_gnuradio/usrp/simple_usrp.py

Simple source exists because actual usrp api is sooo crazy. The goal of
the simple source and simple sink is to provide the most useful options
to the usrp user.

You can change the decimation, but I have never heard of “setting adc
rate” for usrp. I think the adc rate is always 64e6 msamps/s… However
usrp always has new surprises (somehow???). If changing the converter
rate is possible, //somebody// please weigh in here.

-Josh