Hello Josh,
I ran the single USRP 4MS/s channel recorded to four files at 500MS/s script
again for longer durations. I now saw more overruns just as I would with the
four USRP 1MS/s channels recorded to four files at 500MS/s.
I also looked at the GRC script for the older libusrp version. The USRP block
is a custom written one that has four outputs. I'm not sure how the
interleaver/de-interleaver is handled in that custom block istelf, but in the
rest of the GRC script there is no additional interleave or de-interleave block
used. The particular USRP block I'm using was written by a GNURadio user in
2009.
Given all of the above it seems like maybe the combination of ubuntu 12.04 and
libuhd requires more processing power than the older setup that has worked
flawless? It would be nice to make the newer setup work with overruns but I'm
out of ideas.
Thanks, -Tom
________________________________
From: Josh Blum <j...@ettus.com>
To: Tom Hendrick <sdtom...@yahoo.com>
Cc: "discuss-gnuradio@gnu.org" <discuss-gnuradio@gnu.org>
Sent: Sunday, March 10, 2013 10:29 PM
Subject: Re: [Discuss-gnuradio] LibUSRP vs LibUHD Performance on older machines
On 03/08/2013 02:44 PM, Tom Hendrick wrote:
> Hi Josh,
>
> Would you happen to suggest any more setting changes I could try before just
> deciding I need to depend on the older libusrp/gnuradio for recording 4
> channels to disk from a USRP?
On this particular machine, are you able to sustain one channel at 8Msps
but not 4 channels at 2Msps? That might indicate that there isnt enough
headroom for the deinterleaving. The old driver just output interleaved
data, and you would deinterleave samples in a separate block.
-josh
> Thanks, - Tom
>
>
>
>
>
> ________________________________
> From: Josh Blum <j...@ettus.com>
> To: Tom Hendrick <sdtom...@yahoo.com>
> Cc: "discuss-gnuradio@gnu.org" <discuss-gnuradio@gnu.org>
> Sent: Saturday, March 2, 2013 9:18 AM
> Subject: Re: [Discuss-gnuradio] LibUSRP vs LibUHD Performance on older
> machines
>
>
>
> On 03/01/2013 05:16 PM, Tom Hendrick wrote:
>> Josh,
>>
>> Thank you so much for the suggestion. I will try this. I have 4GB of
>> ram and a 4GB swapfile size. Do you recommend any particular setting
>> for set_max_output_buffer(long max_output_buffer)?
>>
>>
>
> Make it 10s of megabytes, see if it helps.
>
>> Should I leave tb.run() as is, or modify the number of n_output_items
>> in conjunction with the
>
> I think that part of the API is deprecated (the argument to run). There
> is a similar call on top block, but Im recommending just the usrp source
> block.
>
>>
>> void set_max_output_buffer(long max_output_buffer)?
>>
>>
>> Also, do you recommend any particular settings using uhd_usrp_probe
>> --args="serial=123456, recv_frame_size=XXXX,num_recv_frames=XXXX",
>> send_frame_size=XXXX,send_recv_frames=XXX"
>>
>>
>> or should I leave it default? The custom 4 channel usrp block in the
>> older gnuradio version had the fusb_block and fusb_nblocks both set
>> to 512*32
>>
>
> Go with the default while trying the above.
>
> -josh
>
>> Thanks, -Tom
>>
>>
>>
>>
>> ________________________________ From: Josh Blum <j...@ettus.com> To:
>> discuss-gnuradio@gnu.org Sent: Friday, March 1, 2013 2:55 PM Subject:
>> Re: [Discuss-gnuradio] LibUSRP vs LibUHD Performance on older
>> machines
>>
>>
>>
>> On 03/01/2013 04:51 PM, Tom Hendrick wrote:
>>> Hello all,
>>>
>>> I've had trouble making a 4 channel USRP samples at 1Ms/s write to
>>> file at 500 kS/s with ubuntu 12.04 and libuhd. I am getting
>>> several overruns and I had tried adjusting some of the parameters
>>> using usrd_probe_devices but with no success. I have a laptop with
>>> a duo core centrino processor which should be enough.
>>>
>>> I've made this 4 channel work successfully with the same exact
>>> laptop and with ubuntu 10.04 and the older version of gnuradio that
>>> uses libusrp. I get no underruns at all even for an entire hour of
>>> writing to file.
>>>
>>>
>>> Has anyone else experienced performance differences between libusrp
>>> and libuhd? I just want to make sure it isn't a configuration
>>> problem or something I'm doing wrong causing the overruns. If its
>>> likely an issue with libuhd, I guess I will just keep a backup of
>>> ubuntu 10.04 and gnuradio libusrp version installation files and
>>> leave my dual boot setup intact.
>>>
>>> Thank you very much, - Tom
>>>
>>>
>>
>> You might try setting a very large output buffer on the usrp source
>> block. I heard this helps (you should be able to call this in python
>> after the block constructs):
>>
>> /*! * \brief Sets max buffer size on all output ports. */ void
>> set_max_output_buffer(long max_output_buffer)
>>
>> -josh
>>
>>>
>>> _______________________________________________ Discuss-gnuradio
>>> mailing list Discuss-gnuradio@gnu.org
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>
>>
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