1. Re: USRP buffering and latencies (Josh Blum)
2. Can not remove the receiving spike (DC component) by advanced
   tune request at USRP N210. (Alex Zhang)
3. Re: USRP with Matlab (Mike McLernon)
4.  How to use UHD USRP2 IFace (Tim Schuschies)
5. Re: USRP with Matlab (Mohamed Ismail)
6. Re: USRP with Matlab (Mike McLernon)
7. Re: USRP with Matlab (Mike McLernon)
8. Re: USRP with Matlab (Mohamed Ismail)

     tune_req = uhd.tune_request(options.freq, 5e6)   # with lo_offset =

Thanks Josh On Mon, Oct 1, 2012 at 9:30 PM, <usrp-users-request@lists.ettus.com> wrote: > Send USRP-users mailing list submissions to > usrp-users@lists.ettus.com > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > or, via email, send a message with subject or body 'help' to > usrp-users-request@lists.ettus.com > > You can reach the person managing the list at > usrp-users-owner@lists.ettus.com > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of USRP-users digest..." > > > Today's Topics: > > 1. Re: USRP buffering and latencies (Josh Blum) > 2. Can not remove the receiving spike (DC component) by advanced > tune request at USRP N210. (Alex Zhang) > 3. Re: USRP with Matlab (Mike McLernon) > 4. How to use UHD USRP2 IFace (Tim Schuschies) > 5. Re: USRP with Matlab (Mohamed Ismail) > 6. Re: USRP with Matlab (Mike McLernon) > 7. Re: USRP with Matlab (Mike McLernon) > 8. Re: USRP with Matlab (Mohamed Ismail) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sun, 30 Sep 2012 16:11:25 -0700 > From: Josh Blum <josh@ettus.com> > To: usrp-users@lists.ettus.com > Subject: Re: [USRP-users] USRP buffering and latencies > Message-ID: <5068D19D.8060803@ettus.com> > Content-Type: text/plain; charset=ISO-8859-1 > > > > On 09/30/2012 03:26 AM, Usrp IITM wrote: > > Hi, > > > > I am trying to find out how USRP implements data buffers in the > hardware. > > I have a few questions regarding this: > > > > 1) Do the USRP and the host (computer) communicate by UDP? Does the UHD > > use VITA49 as encapsulation above the UDP layer? > > > > The packets for the network devices are simple VITA49 on top of UDP > datagrams. Some notes on this: > http://files.ettus.com/uhd_docs/manual/html/stream.html > > > 2) Once the packet (udp) reaches the USRP, where does the USRP store the > > data? > > > > a) Does it have a circular (or a normal) buffer? > > b) What is the size of this buffer? Can this size be changed? > > c) Does the USRP read from this buffer continuously (at the > > sampling rate)? Or does it wait for the buffer to get full? > > > > ---On transmit, there is a 1MB SRAM on the USRP which is used as a > sample FIFO. When this buffer fills, the API call to > usrp_tx_stream->send(...) will actually block until there is space > available on the USRP. > > A software change could be used to shrink how much SRAM can be filled > with samples, but there is no way to increase the buffering without > swapping out the RAM with something larger. > > The USRP will read from this SRAM ASAP when the TX DSP is consuming > samples. > > ---On receive. There is a rather large kernel socket buffer. By default > the UHD sizes it to 50MB, but it can be arbitrary. When the buffer is > full, UDP datagrams are dropped. > > > http://files.ettus.com/uhd_docs/manual/html/transport.html#resize-socket-buffers > > > http://files.ettus.com/uhd_docs/manual/html/general.html#overflow-underflow-notes > > > 3) What is the typical latency of a packet (UDP) to reach the USRP > > (assuming default settings with almost zero cpu load at the host)? > > > > about 100us for gigabit ethernet. See the note about interrupt > coalescing > > http://files.ettus.com/uhd_docs/manual/html/transport.html#latency-optimization > > -josh > > > > ------------------------------ > > Message: 2 > Date: Mon, 1 Oct 2012 01:59:27 -0500 > From: Alex Zhang <cingular.alex@gmail.com> > To: gnuradio mailing list <discuss-gnuradio@gnu.org>, usrp-users > <usrp-users@lists.ettus.com> > Subject: [USRP-users] Can not remove the receiving spike (DC > component) by advanced tune request at USRP N210. > Message-ID: > <CA+FEAnf25ZLWvHsAuJwutNMVRJ0QoCFSQXEUbCK6Vkhn= > xxquw@mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > Hi, > > I always get a strong spike in the attachment, when using uhd_fft to > measure the noise. Please note there is no any signal on the air, only > noise, but I got this spike. > I guess this is the so called DC component. Thus I tried to remove this > spike, as stated in > http://files.ettus.com/uhd_docs/manual/html/general.html#tuning-notes, > using the advanced tuning request. > > My sample rate is 2Ms, so as my understanding, I need to set the lo_offset > as >= 4MHz, to get the spike out my band, like this: > > tune_req = uhd.tune_request(options.freq, 5e6) # with lo_offset = > 5MHz > usrp.set_center_freq(tune_req, 0) > > Then I get the tune result as: > > Tune Result: > Target RF Freq: 2405.000000 (MHz) > Actual RF Freq: 2405.000000 (MHz) > Target DSP Freq: 5.000000 (MHz) > Actual DSP Freq: 5.000000 (MHz) > > However, the spike is still there, almost the same, and the center > frequency is even still the same (this could be due to the some GUI usage)! > I really don't know if the advanced tuning works or not. It seems that the > incoming streaming still contains the DC component. > > Spike of the received noise. > > > [image: Inline image 1] >