Re: [Discuss-gnuradio] USRP1 4 Channel Subdev Issue

[Josh Blum]

On 02/20/2013 02:22 PM, Tom Hendrick wrote:
> Thanks for the suggestion Marcus.
> 
> I tried adjusting those settings by using the following command:
> 
> uhd_usrp_probe --args="serial=123456, 
> recv_frame_size=4096,num_recv_frames=4096"
> The 123456 is replaced with the actual serial number of the usrp1 when I run 
> the command.  
> 
> 
> When I run that command it shows the USRP1 configuration settings and the 
> daughtercard and then at the bottom it says "Segmentation fault (core 
> dumped)".  This happens with other values of recv_frame_size and 
> num_recv_frames.  Does anyone know what I'm doing wrong or is this even the 
> right way to change those settings?
> 
> What are the default values in case I need to set them back to what they 
> were?  I couldn't find this anywhere in the UHD documentation.
> 

The values arent sticky, so you dont need to worry about that. The
default libusb xfer size if 16384 bytes.

I think the segfault comes from the number of frames. The default is 16,
and you can change this, but 4k is probably way more pending LUTs than
libusb can handle.

-josh

> Thank you, - Tom
> 
> 
> 
> 
> ________________________________
>  From: Marcus D. Leech <address@hidden>
> To: Tom Hendrick <address@hidden> 
> Cc: "address@hidden" <address@hidden> 
> Sent: Wednesday, February 20, 2013 9:53 AM
> Subject: Re: [Discuss-gnuradio] USRP1 4 Channel Subdev Issue
>  
> 
> I tried the suggestion from Marcus and was able to get the USRP1 to work with 
> 4 real channels.  I have a simple GRC script which  samples the USRP at 1MS/s 
> and then resamples the signal to 500kS/s and then writes to a file.  I am 
> getting continuous Overruns with this GRC script on my laptop.  
>>
>> I have the same GRC script with the older GNURadio and when I
>         ran it again on the same laptop (I booted up a prior version of
>         ubuntu with an older gnuradio version that uses the USRP class
>         not UHD) it writes to file with no Overruns at all.  I saw that
>         the custom quad channel USRP block has an fusb_block and
>         fusb_nblocks setting.  These are both set to 512*32 but if I
>         lower them to something like 64*32 I start to see the Overruns.
>>
>> Are there similar type settings I can adjust on the 3.6.2
>         version of GRC or GNURadio python scripts to get rid of the
>         overruns?  I'm not sure if this is possible but I would like to
>         not have to boot into an older ubuntu version when I need 4 real
>         channels.  The only thing that comes to mind is to adjust
>         noutput_items and I tried this but it didn't eliminate the
>         overruns.
>>
>> Thank you, -Tom
>>
>>
>>
>>
> http://files.ettus.com/uhd_docs/manual/html/transport.html#usb-transport-libusb
> 
> The USB parameters shown there can be passed as device args
> 
> 
> 
> 
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