[USRP-users] B210 RF DC Offset Calibration Failure

Marcus D. Leech mleech at ripnet.com
Tue Dec 16 18:20:26 EST 2014


On 12/16/2014 05:58 PM, Perelman, Nathan via USRP-users wrote:
>
> So is there no way to reliably sample at 61.44 MHz from a B210?
>
> -Nathan
>
The highest sample-rate on the B210 *when using both channels* is 
30.72Msps, whereas in single-channel mode, it should be 61.44Msps, 
provided you
   make the master clock 61.44MHz--the default master clock if you don't 
specify anything is 32MHz.

The AD9361 supports a maximum of 30.72Msps when you're streaming both 
sides out of it, and that is a restriction on the way the clocking
   works on that chip, not an arbitrary limitation based on FPGA policy 
or anything like that, as far as I know.

Not sure why master clock above 56MHz doesn't work--it should, and 
perhaps Balint or Ben or one of the other B2xx-involved R&D people could
   comment.  I know that I've set 61.44MHz master clock on my B210 in 
the past, and that has worked OK, but perhaps this is a "chip by chip"
   thing.  There's no hint of that in the AD9361 data sheet.


> *From:*USRP-users [mailto:usrp-users-bounces at lists.ettus.com] *On 
> Behalf Of *Perelman, Nathan via USRP-users
> *Sent:* Monday, December 1, 2014 6:59 PM
> *To:* Ian Buckley
> *Cc:* usrp-users at lists.ettus.com
> *Subject:* Re: [USRP-users] B210 RF DC Offset Calibration Failure
>
> As advertised by the driver, the error does go away when I request a 
> master clock rate of 56 MHz. Other values between 56 and 61.44 MHz did 
> not work (I tried 57, 58, and 60). I was hoping to be able to sample 
> at 61.44 MHz for my application.
>
> -Nathan
>
> *From:*Ian Buckley [mailto:ianb at ionconcepts.com]
> *Sent:* Monday, December 1, 2014 6:16 PM
> *To:* Perelman, Nathan
> *Cc:* usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>
> *Subject:* Re: [USRP-users] B210 RF DC Offset Calibration Failure
>
> This is a vague answer since I've never worked on this aspect of 
> AD9361 and someone may respond with a better response.....
>
> My recollection is that despite the actually radio being spec'ed to 
> 61.44MHz, experience demonstrated that some of the internal algorithms 
> that perform calibrations start to have problems converging above 
> 56MHz, which generally results in larger elapsed times before the 
> device is ready to by used after configuration. Thus the origins of 
> the warning message UHD gives for rates >56MHz. I don't recall hearing 
> a good reason "why" this should be so from any ADI engineering folks.
>
> So perhaps slow to converge manifests as failed to converge for some 
> possible configurations? What happens if you back it off a little from 
> the limit..say 61.0HMz?
>
> -Ian
>
> On Dec 1, 2014, at 1:58 PM, "Perelman, Nathan via USRP-users" 
> <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>> wrote:
>
> I'm seeing this error attempting to use a B210 with a master clock 
> rate of 61.44 MHz. This is with UHD 3.8.0. I've been just trying to 
> test it out with the benchmark_rate application, but this is what happens:
>
> $ ./benchmark_rate --rx_rate 61.44e6 --channels 0 --args 
> "master_clock_rate=61.44e6" --rx_cpu=sc16
>
> linux; GNU C++ version 4.8.3 20140624 (Red Hat 4.8.3-1); Boost_105500; 
> UHD_003.008.000-0-unknown
>
> Creating the usrp device with: master_clock_rate=61.44e6...
>
> -- Operating over USB 3.
>
> -- Detecting internal GPSDO.... Found an internal GPSDO
>
> -- Initialize CODEC control...
>
> -- Initialize Radio control...
>
> -- Performing register loopback test... pass
>
> -- Performing register loopback test... pass
>
> -- Performing CODEC loopback test... pass
>
> -- Performing CODEC loopback test... pass
>
> -- Asking for clock rate 61.440000 MHz
>
> UHD Warning:
>
>     The requested clock rate 61.440000 MHz may cause slow configuration.
>
>     The driver recommends a master clock rate less than 56.000000 MHz.
>
> Error: RuntimeError: [ad9361_device_t] RF DC Offset Calibration Failure
>
> I get the same error for other rates I've tried in excess of 56 MHz. 
> Any idea what causes this error and what I could do to resolve it? Thanks.
>
> -Nathan
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com


-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/attachments/20141216/7cbf7af6/attachment-0002.html>


More information about the USRP-users mailing list