[USRP-users] b200 Overflows

Robert Kossler Robert.D.Kossler.3 at nd.edu
Mon Sep 29 10:09:18 EDT 2014


Even after upgrade, sc12 only works with cpu format fc32 (not sc16).  So,
if you want to use sc12, you need to choose fc32 as cpu format.
Rob

On Mon, Sep 29, 2014 at 10:04 AM, Marcus D. Leech via USRP-users <
usrp-users at lists.ettus.com> wrote:

>  On 09/29/2014 03:00 AM, Simon Brown wrote:
>
>  Marcus,
>
>
>
> Using the 007.003.001 codebase uhd::stream_args_t(“sc16”, “sc12”) crashes
> inside usrp->get_rx_stream. I don’t see any reference to sc12 in the
> https://github.com/EttusResearch/uhd/blob/master/CHANGELOG, so I’m a bit
> lost now.
>
>
>
> Please clarify (I’ve read the source) if I get an overrun then the data is
> being delivered from the B200 faster than the UHD.dll is reading it? If
> this is the case I also believe that there’s no way I can tell the
> underlying code to flush the LibUSB buffers?
>
>
>
> I’m currently having considerable success with all Ettus hardware flavours
> but am a tad stuck with the whole UHD concept / way of life, your help is
> greatly appreciated.
>
>
>
> Simon Brown G4ELI
> http://v2.sdr-radio.com
>
>
> http://files.ettus.com/manual/structuhd_1_1stream__args__t.html#aa54b7dc3e2c71d11c774d8b4a15984cc
>
> Describes the components of stream_args_t.  In particular, the first
> component is the desired host-side ("CPU") format, the second the wire-side
>   format.
>
> I think sc12 was introduced after UHD 3.7.1, so upgrade.
>
>
>
>
>
> *From:* Marcus D. Leech [mailto:mleech at ripnet.com <mleech at ripnet.com>]
> *Sent:* 27 September 2014 19:41
> *To:* Simon Brown
> *Cc:* usrp-users at lists.ettus.com
> *Subject:* Re: [USRP-users] b200 Overflows
>
>
>
> On 09/27/2014 02:30 PM, Simon Brown via USRP-users wrote:
>
> Hi Marcus,
>
>
>
> I’ll try sc12 tomorrow, possibly later this evening. I’m currently
> preparing food and adding some diagnostics.
>
>
>
> It’s probably in the manual, but is there a way to determine the most
> efficient format for a device without losing resolution, for example sc12
> for b200, (maybe) sc16 or fc21 for the N210 etc.? I would like to reduce
> any network / bus traffic where possible.
>
>
>
> Simon Brown G4ELI
> http://v2.sdr-radio.com
>
> The number of over-the-wire-formats is strictly-limited---it's not
> open-ended.
>
> For all products other than B200, the only available formats are sc16 and
> sc8.   B200 has the additional sc12 over-the-wire format.
>
> These "wire formats" are then converted by the driver into one of a few
> host-side formats, the most natural for a lot of work being
>   fc32.
>
> The idea behind "wire formats" is to preserve a strictly-limited resource,
> namely, over-the-wire bandwidth.  No amount of "buying the very best"
>   1GiGe controller, for example, will get you beyond 1Gigabit of bandwidth
> over that medium.  Which is why to support 50Msps on the N2xx, you
>   have to use 8-bit wire format.    On the B200, you can reduce USB bus
> bandwidth, but preserve ADC/DAC dynamic range by using SC12.  I think
>   that only really "plays out" (normally) over USB-2.0.  Over USB-3.0, you
> *should* have plenty of bandwidth available, at least over the USB-3.0
>   bus and inside the controller.   But outside the controller, there may
> be host-bus limitations that may drive on to using more
> byte-per-second-conserving
>   formats.
>
>
>
>
>
> *From:* USRP-users [mailto:usrp-users-bounces at lists.ettus.com
> <usrp-users-bounces at lists.ettus.com>] *On Behalf Of *Marcus D. Leech via
> USRP-users
> *Sent:* 27 September 2014 19:11
> *To:* usrp-users at lists.ettus.com
> *Subject:* Re: [USRP-users] b200 Overflows
>
>
>
> On 09/27/2014 02:00 PM, Simon Brown via USRP-users wrote:
>
> Thanks,
>
>
>
> I’ve tried changing these, still get overruns with sample rates of 8MS/s
> or higher.
>
>
>
> Simon Brown G4ELI
> http://v2.sdr-radio.com
>
>
>
> Are you sure that your USB-3.0 interface is actually dealing with the
> device as a USB-3.0 and not a USB-2.0 device?
>
> If you specify a wire-format of sc8 or sc12, do the overruns go away?
> This will help distinguish between cases involving CPU exhaustion, and
> interior
>   bus deficiencies  (I found this on one of my embedded systems--could
> sustain only 6.4Msps with full-width samples, but was perfectly happy to
>   stream 12.8Msps with 8-bit samples).
>
>
>
>
>   *From:* USRP-users [mailto:usrp-users-bounces at lists.ettus.com
> <usrp-users-bounces at lists.ettus.com>] *On Behalf Of *Marcus D. Leech via
> USRP-users
> *Sent:* 26 September 2014 20:03
> *To:* usrp-users at lists.ettus.com
> *Subject:* Re: [USRP-users] b200 Overflows
>
>
>
> On 09/26/2014 02:18 PM, Simon Brown via USRP-users wrote:
>
> Hi,
>
>
>
> Windows 64-bit: I’m streaming nicely, none of my threads indicate CPU
> problems (plenty of headroom). At 8MB/s and higher I’m getting fastpath
> Overrun messages every second or so even though I’m pulling data from the
> b200 as fast as it’s available, I am not CPU limited in any way. Using
> Intel USB 3.
>
>
>
> FWIW I don’t see any way to tune the uhd::rx_streamer – bigger / more
> buffers, also I don’t see any way to flush either.
>
>
>
> Interestingly if I get my CUDA card working harder (more work on the bus)
> the Overrun messages appear more frequently. I7 4770k, good motherboard
> (can’t remember what).
>
>
>
> Any suggestions?
>
>
>
> Simon Brown G4ELI
> http://v2.sdr-radio.com
>
>
>
>
>
>
>
>
>  _______________________________________________
>
> USRP-users mailing list
>
> USRP-users at lists.ettus.com
>
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>  The USB transport parameters can be tweaked:
>
> http://files.ettus.com/manual/page_transport.html#transport_usb_params
>
>
>
>
>
>
>
> _______________________________________________
>
> 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
>
>
>
>
>  _______________________________________________
>
> 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 Consortiumhttp://www.sbrac.org
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/attachments/20140929/9108f951/attachment-0002.html>


More information about the USRP-users mailing list