Hi Sanjoy,

 if you have an octoclock, you don't need the connection from the
 first X310 to the octoclock. And you *must* set all USRPs to
 external, if you want to use the external clock for all USRPs.

 So, your diagram is still impossible, because it includes a
 loopback on the leftmost X310. I don't understand why you think
 you need to make the connection from the left USRP to the
 Octoclock, could you explain?


 Best regards,
 Marcus


 On 27.10.2016 10:32, Sanjoy Basak wrote:

 Hi Marcus,
 Thanks for the explanation. Now I understand. 
 We have 4 X310s and one equipped with GPSDO. We are trying to
 make time and phase synchronized MIMO operation. So the final
 goal is to make this configuration work.
 Inline image 1

 As we already have one GPSDO module, we are willing to buy one
 Octoclock without GPSDO. It would also save some money. 
 But if I want to make this configuration work, I will have to put
 all the USRPs on external. If I put one on internal and others on
 external, then it would be the same as daisy chained. 

 Could you please tell me if this configuration is anyhow possible
 with Octoclock (without GPSDO), by modifying UHD code or using
 any patch. 
 Or we must buy Octoclock-G.

 Best regards
 Sanjoy



 On Wed, Oct 26, 2016 at 4:50 PM, Marcus Müller via USRP-users
 <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>
 wrote:

     Hi Sanjoy,

     you've got a misunderstanding there.

     If you set the reference input to external, the USRP stops
     using its own reference oscillator, but uses what you feed in
     externally.

     So, the USRP used to generate the reference for the other one
     must be set to use its internal oscillator, or else there's
     no active 10MHz reference in your overall system.

     Best regards,

     Marcus


     On 10/26/2016 04:43 PM, Sanjoy Basak via USRP-users wrote:

     Hello everyone,
     I am planning to make the following configuration to test
     the phase and time coherence between 2 X310s. One X310 is
     with GPSDO. I am taking 10 MHz reference and 1 pps signal
     from that usrp and then feed both USRPs with the same signal
     distributed from a T connector.  


     Inline image 3

     However, it did not work.

     Afterwards I found out that the problem is in this
     configuration. If I take the 10 MHz signal and 1 pps signal
     from ref_out and pps_out and feed that USRP with the same
     signal (with time and clock reference External), it does not
     work.
     Inline image 4

     Could anyone tell me how to make it work. I am using uhd 3.9.2

     Best regards
     Sanjoy




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Dear Sanjok, as explained, you can't use an internal and an external reference at the same time; there's a causality problem there... What you should do is just take the GPSDO from the first USRP and installl it in the Octoclock. Alternatively, you can also just use the first USRP (with the GPSDO installed) as "master" and don't make a connection from the octoclock to that USRP, but then you'll have to measure and calibrate the delay between that USRP and the others. Best regards, Marcus On 27.10.2016 11:31, Sanjoy Basak wrote: > Hi Marcus, > I actually have 4 X310s in total. With these I am trying to make a > MIMO receive array, with as many rx elements as possible. My > application is to implement DoA estimation of incoming signal with > Music/digital beamforming (test both actually). Now if I am not > including one X310 (the reference feeding USRP) then I am losing rx > elements. I also want a complete coherent system. > > My boss wanted me to make sure if buying one Octoclock without gpsdo > is enough. > So I am looking at the possibilities. > If its not possible then we will go for the Octoclock-G. > > Best regards > Sanjoy > > > > On Thu, Oct 27, 2016 at 10:43 AM, Marcus Müller > <marcus.mueller@ettus.com <mailto:marcus.mueller@ettus.com>> wrote: > > Hi Sanjoy, > > if you have an octoclock, you don't need the connection from the > first X310 to the octoclock. And you *must* set all USRPs to > external, if you want to use the external clock for all USRPs. > > So, your diagram is still impossible, because it includes a > loopback on the leftmost X310. I don't understand why you think > you need to make the connection from the left USRP to the > Octoclock, could you explain? > > > Best regards, > Marcus > > > On 27.10.2016 10:32, Sanjoy Basak wrote: >> Hi Marcus, >> Thanks for the explanation. Now I understand. >> We have 4 X310s and one equipped with GPSDO. We are trying to >> make time and phase synchronized MIMO operation. So the final >> goal is to make this configuration work. >> Inline image 1 >> >> As we already have one GPSDO module, we are willing to buy one >> Octoclock without GPSDO. It would also save some money. >> But if I want to make this configuration work, I will have to put >> all the USRPs on external. If I put one on internal and others on >> external, then it would be the same as daisy chained. >> >> Could you please tell me if this configuration is anyhow possible >> with Octoclock (without GPSDO), by modifying UHD code or using >> any patch. >> Or we must buy Octoclock-G. >> >> Best regards >> Sanjoy >> >> >> >> On Wed, Oct 26, 2016 at 4:50 PM, Marcus Müller via USRP-users >> <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> >> wrote: >> >> Hi Sanjoy, >> >> you've got a misunderstanding there. >> >> If you set the reference input to external, the USRP stops >> using its own reference oscillator, but uses what you feed in >> externally. >> >> So, the USRP used to generate the reference for the other one >> must be set to use its internal oscillator, or else there's >> no active 10MHz reference in your overall system. >> >> Best regards, >> >> Marcus >> >> >> On 10/26/2016 04:43 PM, Sanjoy Basak via USRP-users wrote: >>> Hello everyone, >>> I am planning to make the following configuration to test >>> the phase and time coherence between 2 X310s. One X310 is >>> with GPSDO. I am taking 10 MHz reference and 1 pps signal >>> from that usrp and then feed both USRPs with the same signal >>> distributed from a T connector. >>> >>> >>> Inline image 3 >>> >>> However, it did not work. >>> >>> Afterwards I found out that the problem is in this >>> configuration. If I take the 10 MHz signal and 1 pps signal >>> from ref_out and pps_out and feed that USRP with the same >>> signal (with time and clock reference External), it does not >>> work. >>> Inline image 4 >>> >>> Could anyone tell me how to make it work. I am using uhd 3.9.2 >>> >>> Best regards >>> Sanjoy >>> >>> >>> >>> >>> _______________________________________________ >>> USRP-users mailing list >>> USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> >> _______________________________________________ USRP-users >> mailing list USRP-users@lists.ettus.com >> <mailto:USRP-users@lists.ettus.com> >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> >> >>