I forgot to mention that I had set three channels to null and kept just one
writing to a file. In this case I still see overruns.
Also if I drop the sampling rate to 500 MS/s on all four channels but leave
them all writing to file at 500 kS/s I don't see any overruns at all. The
problem is I want 1 MS/s sampling for a flatter frequency response.
Does anyone have advice on anything else I can try? Again in the older version
of GNURadio/GRC, I could run four channels at 1MS/s and write all four to
500MS/s sampled files without any overruns at all.
Thank you, -Tom
________________________________
From: Tom Hendrick <[email protected]>
To: "[email protected]" <[email protected]>; "[email protected]"
<[email protected]>
Sent: Thursday, February 21, 2013 2:20 PM
Subject: Re: [Discuss-gnuradio] USRP1 4 Channel Subdev Issue
Thanks Josh.
I've tried some different combinations of uhd_usrp_probe --args="serial=123456,
recv_frame_size=16384,num_recv_frames=16" and varied recv_frame_size up to
something really high like 1,000,000 and num_recv_frames up to 400 and didn't
get the segementation fault error.
When I run my 4 channel RX script after trying some different configurations I
am still getting overruns. If I change the USRP sampling rate to 500kS/s but
leave the file rate at 500kS/s the overruns go away however I want to sample
the USRP at 1MS/s to have a flatter frequency response. This leads me to think
the Overruns are not caused by the file writing part.
The fusb_block and fusb_nblocks setting were both set to 512*32 in the older
GNURadio version and custom USRP 4 channel source block. The same script
in the older GNURadio version still runs with no Overruns even at 1Ms/s for
each of the 4 USRP channels.
Is there anything else I can try? Do I need to also alter the send_frame_size
and num_send_frames in the uhd_usrp_probe calls?
Thank you, Tom
________________________________
From: Josh Blum <[email protected]>
To: Tom Hendrick <[email protected]>; "[email protected]"
<[email protected]>
Sent: Wednesday, February 20, 2013 4:34 PM
Subject: Re: [Discuss-gnuradio] USRP1 4 Channel Subdev Issue
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 <[email protected]>
> To: Tom Hendrick <[email protected]>
> Cc: "[email protected]" <[email protected]>
> 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
>
>
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> [email protected]
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
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