# Mulitple USRP Stream Confusion **URL:** \ **Category:** GNU Radio\ **Created:** [September 30, 2014, 10:03pm UTC](https://www.ruby-forum.com/t/mulitple-usrp-stream-confusion/232290 "2014-09-30T22:03:27Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [September 30, 2014, 10:03pm UTC](https://www.ruby-forum.com/t/mulitple-usrp-stream-confusion/232290/1 "2014-09-30T22:03:27Z")
Hello! I am having trouble trying to create a continuous stream of complex shorts from multiple (2) X310 USRPs (each running 2 channels) over a single 1gigE switch (at a very low sampling rate); currently it appears as though I can only stream from one USRP at a time and I can’t seem to figure out why. I should note I don’t have this problem running each USRP on its own dedicated network (but unfortunately that won’t be possible moving forward). To date, I have been using the rx\_multi\_samples example provided with UHD (source 003.007.002). I dont seem to have any issue connecting to both USRPs and setting the parameters via the args=addr0=192.168.10.2, addr1=192.168.10.3 command. It is just that when I call rx\_stream-\>recv only the lights on the USRP which was listed first in args turn on. The subdev spec and channel selection for each USRP is set to “A:A B:A” and “0,1” and the incoming data from rx\_stream is two channels of complex shorts (not 4 like I would expect from 2 USRPs). Do I have to initiate the streams differently or am I missing something? Thanks! -Andrew ---
**Author:** ![DaigleS\_AndrewS10](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed655f/32.png) [@DaigleS\_AndrewS10](https://www.ruby-forum.com/u/DaigleS_AndrewS10)\ **Post date:** [September 30, 2014, 11:05pm UTC](https://www.ruby-forum.com/t/mulitple-usrp-stream-confusion/232290/2 "2014-09-30T23:05:44Z")
Hey Andrew, First, that subdev seems off – I’d assume it’s something like “A:0 B:0”? Next, I’m not even sure what you mean you set the channels to “0,1” on both devices. You should have 1 streamer, with a channel setting of “0,1,2,3”. The ‘args’ string seems correct. Does this help? M ---
**Author:** ![DaigleS\_AndrewS10](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed655f/32.png) [@DaigleS\_AndrewS10](https://www.ruby-forum.com/u/DaigleS_AndrewS10)\ **Post date:** [October 1, 2014, 2:57pm UTC](https://www.ruby-forum.com/t/mulitple-usrp-stream-confusion/232290/3 "2014-10-01T14:57:54Z")
Hello Martin, Thanks for the response. I should have mentioned that the subdev spec was set to A:A B:A because I am using the basic RX boards. Trying “0:A 0:B” instead gives the following error: “0:A is not a valid rx subdevice specification on mboard 0. possible values are: [A:AB, A:BA, A:A, A:B, B:AB, B:BA, B:A, B:B].” Your suggestion to set the channel as 0,1,2,3 seemed to work perfectly (not sure how I missed that) as now I am getting four complex shorts out of my setup (an example of what is now in the buffer is shown below): (-3,-2)(3,0)(-1,0)(1,0) (2,-1)(0,0)(-3,0)(-2,0) (3,5)(1,0)(-1,0)(-1,0) (4,-2)(-4,0)(-1,0)(2,0) In getting the channels to stream however, I ran across another strange occurrence. After looking at the FFT data it appears as though the following commands only set the frequency of the first channel: uhd::tune\_request\_t tune\_request(freq); usrp-\>set\_rx\_freq(tune\_request); Channels 1,2, and 3 all show single peaks centered at 0 Hz in the FFT window. I was able to correct this by directly setting the frequency of each channel independently (as shown below) , but I was under the impression that when you create the usrp devices to begin with it should apply commands across all channels? uhd::tune\_request\_t tune\_request(freq); usrp-\>set\_rx\_freq(tune\_request, 0); usrp-\>set\_rx\_freq(tune\_request, 1); usrp-\>set\_rx\_freq(tune\_request, 2); usrp-\>set\_rx\_freq(tune\_request, 3); Thanks again! This is really a great product and I look forward to getting more acquainted with what it can do. -Andrew * * * From: [discuss-gnuradio-bounces+andrew.daigle=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+andrew.daigle=removed_email_address@domain.invalid) [discuss-gnuradio-bounces+andrew.daigle=removed\_email\_address@domain.invalid] on behalf of Martin B. [removed\_email\_address@domain.invalid] Sent: Tuesday, September 30, 2014 5:04 PM To: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Subject: Re: [Discuss-gnuradio] Mulitple USRP Stream Confusion Hey Andrew, First, that subdev seems off – I’d assume it’s something like “A:0 B:0”? Next, I’m not even sure what you mean you set the channels to “0,1” on both devices. You should have 1 streamer, with a channel setting of “0,1,2,3”. The ‘args’ string seems correct. Does this help? M On 30.09.2014 13:01, Daigle, Andrew - 1008 - MITLL wrote: > To date, I have been using the rx\_multi\_samples example provided with > Thanks! > > -Andrew > > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) * * * Discuss-gnuradio mailing list [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > **[Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)** ---
**Author:** ![DaigleS\_AndrewS10](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed655f/32.png) [@DaigleS\_AndrewS10](https://www.ruby-forum.com/u/DaigleS_AndrewS10)\ **Post date:** [October 1, 2014, 3:49pm UTC](https://www.ruby-forum.com/t/mulitple-usrp-stream-confusion/232290/4 "2014-10-01T15:49:12Z")
No, since you can easily have independent channels inside a multi-usrp block, gain and frequency parameters need to be set for each channel. You can see how this works when you do the same thing from within GRC, and look at the generated code. On 2014-10-01 08:54, Daigle, Andrew - 1008 - MITLL wrote: > (3,5)(1,0)(-1,0)(-1,0) > usrp-\>set\_rx\_freq(tune\_request, 0); > To: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > > M > > On 30.09.2014 13:01, Daigle, Andrew - 1008 - MITLL wrote: > > > Hello! I am having trouble trying to create a continuous stream of complex > > shorts from multiple (2) X310 USRPs (each running 2 channels) over a single 1gigE > > switch (at a very low sampling rate); currently it appears as though I can only > > stream from one USRP at a time and I can’t seem to figure out why. I should note I > > don’t have this problem running each USRP on its own dedicated network (but > > unfortunately that won’t be possible moving forward). To date, I have been using > > the rx\_multi\_samples example provided with UHD (source 003.007.002). I don’t seem > > to have any issue connecting to both USRPs and setting the parameters via the > > args=“addr0=192.168.10.2, addr1=192.168.10.3” command. It is just that when I call > > rx\_stream-\>recv only the lights on the USRP which was listed first in args turn > > on. The subdev spec and channel selection for each USRP is set to “A:A B:A” and > > “0,1” and the incoming data from rx\_stream is two channels of complex shorts (not > > 4 like I would expect from 2 > > USRPs). Do I have to initiate the streams differently or am I missing > > something? Thanks! -Andrew > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Discuss-gnuradio mailing > > list [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) [1] > > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) [1] > > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) [1] Links: