[USRP-users] synchronizing multiple USRP N310

Marcus D. Leech patchvonbraun at gmail.com
Fri Feb 22 09:09:06 EST 2019


On 02/22/2019 08:15 AM, Jorge Chen wrote:
> Hi Marcus
>
> Thanks for your reply.
>
> Since I thought it works in the case using channel 0,4 with default 
> subdev spec setup(“A:0 A:1 B:0 B:1”), so I ignore setting the subdev spec.
> However, I add the subdev spec setting and test again, but still 
> failed to transmit synchronized signal from 2 N310s.
> Any other advices?
Yesterday, you said you failed to transmit *ANY* signal.  Please clarify 
as to whether you mean you're transmitting, but the result is
   unsynchronized, or whether there's no signal at all.



>
>
> To take a note, Q3 yesterday,3. When does the N310 re-initialize the 
> daughter board?
> -> I found that the time is after set_clock_source(ref) and 
> set_time_source(pps) commands.
>
> All the best!
> Jorge
>
>
> Marcus D. Leech via USRP-users <usrp-users at lists.ettus.com 
> <mailto:usrp-users at lists.ettus.com>> 於 2019年2月22日 週五,上午3:27寫道:
>
>     On 02/21/2019 10:18 AM, Jorge Chen via USRP-users wrote:
>>     Hi USRP Users
>>
>>     I tried to synchronize 2 N310s throught the external PPS and
>>     reference clock, and tested by the application below.
>>     */tx_waveforms.exe  --args
>>     "addr0=192.168.30.3,addr1=192.168.40.3,clock_source=external,time_source=external,master_clock_rate=122.88e6"
>>     --rate 30.72e6 --freq 3.5e9 --wave-type SINE --wave-freq 10e6
>>     --gain 20 --channels "0,4"--ref "external" --pps "external"/*
>>     The program runs without errors, but no signal outputs from the
>>     corresponding channels. ( No sine waveform on the scope, and the
>>     LED light are dark.)
>     You have not included a subdev specification, so it's not going to
>     be able to intuit what you mean.
>
>     https://kb.ettus.com/N300/N310_Getting_Started_Guides#Subdevice_Specification_Mapping
>
>
>
>>
>>     I've checked if the external PPS is available by the application
>>     "test_pps_input.exe".
>>     And if I only use 1 N310, it works normally.
>>     But failed in the 2 N310s synchronized case.
>>
>>     The OS is Win10, and I use the UHD 3.13.1.
>>
>>     My questions are:
>>     1. Is the commands or the hardware/environment setting causing
>>     the failure on synchronizing the 2 N310s?
>>     2. I found the eeprom_version and the rev information are
>>     different, does this difference affect?
>>     And two further questions:
>>     3. When does the N310 re-initialize the daughter board? In the
>>     log (please see the attached file), it executes re-initializing
>>     routine 3 times.
>>     4. What's the difference between specifying
>>     "clock_source=external, time_source=external" in the device
>>     argument and use the UHD API set_time_source("external"),and
>>     set_clock_source("external") if I'd like to synchronize multiple
>>     N310s.
>>     Are they both necessary?
>>
>>
>>     |    /
>>     |   |       Mboard: ni-n3xx-3151CB0
>>     |   |   eeprom_version: 1
>>     |   |   mpm_version: 3.13.1.0-gbbce3e45
>>     |   |   pid: 16962
>>     |   |   product: n310
>>     |   |   rev: 5
>>     |   |   rpc_connection: remote
>>     |   |   serial: 3151CB0
>>     |   |   type: n3xx
>>     |   |   MPM Version: 1.2
>>     |   |   FPGA Version: 5.2
>>     |   |   FPGA git hash: d0360f7.clean
>>     |   |   RFNoC capable: Yes
>>     |   |
>>     |   |   Time sources:  internal, external, gpsdo, sfp0
>>     |   |   Clock sources: external, internal, gpsdo
>>     |   |   Sensors: temp, gps_locked, gps_time, gps_sky, gps_tpv,
>>     ref_locked, fan
>>     | _____________________________________________________
>>     |    /
>>     |   |       Mboard: ni-n3xx-3175D90
>>     |   |   eeprom_version: 2
>>     |   |   mpm_version: 3.13.1.0-gbbce3e45
>>     |   |   pid: 16962
>>     |   |   product: n310
>>     |   |   rev: 6
>>     |   |   rpc_connection: remote
>>     |   |   serial: 3175D90
>>     |   |   type: n3xx
>>     |   |   MPM Version: 1.2
>>     |   |   FPGA Version: 5.2
>>     |   |   FPGA git hash: d0360f7.clean
>>     |   |   RFNoC capable: Yes
>>     |   |
>>     |   |   Time sources:  internal, external, gpsdo, sfp0
>>     |   |   Clock sources: external, internal, gpsdo
>>     |   |   Sensors: gps_locked, fan, ref_locked, gps_tpv, gps_sky,
>>     gps_time, temp
>>
>>
>>
>>     Any feedback or help are appreciated!
>>
>>     All the best!
>>     Jorge
>>
>>
>>     Florian Kaltenberger via USRP-users <usrp-users at lists.ettus.com
>>     <mailto:usrp-users at lists.ettus.com>> 於 2018年12月20日 週四 下午
>>     4:48寫道:
>>
>>         Hi Michael,
>>
>>         halleluja! that was it! Thanks for spotting this.
>>
>>         Florian.
>>
>>         On 20/12/2018 02:34, Michael West wrote:
>>>         Hi Florian,
>>>
>>>         The device arguments are "clock_source" and "time_source". 
>>>         I noticed in your command you had them as "clock_src" and
>>>         "time_src".  That may be the source of the problem.
>>>
>>>         Regards,
>>>         Michael
>>>
>>>         On Mon, Dec 10, 2018 at 11:33 AM Florian Kaltenberger via
>>>         USRP-users <usrp-users at lists.ettus.com
>>>         <mailto:usrp-users at lists.ettus.com>> wrote:
>>>
>>>             Dear Nate,
>>>
>>>             no it says something like this is not supported with the
>>>             N310 and I should pass it using the args options. Sorry,
>>>             I don't have access to the N310 right now, so I can't
>>>             give you the exact message, but I have tried that.
>>>
>>>             Florian.
>>>
>>>             On 10/12/2018 19:00, Nate Temple wrote:
>>>>             Hi Florian,
>>>>
>>>>             If you pass the arg  "--ref external" to tx_waveforms,
>>>>             does it resolve this frequency offset?
>>>>
>>>>             https://github.com/EttusResearch/uhd/blob/master/host/examples/tx_waveforms.cpp#L62
>>>>
>>>>             Regards,
>>>>             Nate Temple
>>>>
>>>>             On Thu, Dec 6, 2018 at 12:22 AM Florian Kaltenberger
>>>>             via USRP-users <usrp-users at lists.ettus.com
>>>>             <mailto:usrp-users at lists.ettus.com>> wrote:
>>>>
>>>>                 Hi Marcus,
>>>>
>>>>                 I have measured this with a spectrum analyzer
>>>>                 simply by setting markers to the peak of the
>>>>                 sinusoid (one marker per measured USRP) and then
>>>>                 taking the delta.
>>>>
>>>>                 Could it be that the USRP is ignoring the external
>>>>                 reference when used alone? Remember, I am doing the
>>>>                 test with one USRP at a time, as the test using
>>>>                 multiple USRP simultaneously does not work.
>>>>
>>>>                 Florian.
>>>>
>>>>                 On 06/12/2018 00:29, Marcus Müller wrote:
>>>>>                 oh! That means 341 ppb frequency error, which *really* shouldn't be
>>>>>                 happening.
>>>>>
>>>>>                 I'd like to get some statistics of that error, how are you measuring
>>>>>                 it?
>>>>>
>>>>>                 Best regards,
>>>>>                 Marcus
>>>>>
>>>>>                 On Wed, 2018-12-05 at 12:55 +0100, Florian Kaltenberger wrote:
>>>>>>                 Sorry typo. I did use a frequency of 3.51GHz.
>>>>>>
>>>>>>>                 On 5 Dec 2018, at 12:54, Marcus Müller<marcus.mueller at ettus.com>  <mailto:marcus.mueller at ettus.com>
>>>>>>>                 wrote:
>>>>>>>
>>>>>>>                 Hi Florian,
>>>>>>>
>>>>>>>                 trying to get my head to understand the order of problems here:
>>>>>>>                 Could you try to use a higher frequency (say, --freq 2e9 instead of
>>>>>>>                 3.5e6)?
>>>>>>>                 I'd thing 3.51 MHz is out of range for the N310, anyway?
>>>>>>>
>>>>>>>                 Best regards,
>>>>>>>                 Marcus
>>>>>>>
>>>>>>>                 On Wed, 2018-12-05 at 11:49 +0100, Florian Kaltenberger via USRP-
>>>>>>>                 users
>>>>>>>                 wrote:
>>>>>>>>                 So I can confirm that there is a frequency offset between the two
>>>>>>>>                 USRP N310s when using only an octoclock (10MHz + PPS) to
>>>>>>>>                 synchronize.
>>>>>>>>                 I have measured with the tx_waveforms program
>>>>>>>>                 ./tx_waveforms --args
>>>>>>>>                 "addr=192.168.x.2,time_src=external,clock_src=external,master_clo
>>>>>>>>                 ck_r
>>>>>>>>                 ate=122.88e6" --rate 122.88e6 --freq 3.51e6 --wave-type SINE --
>>>>>>>>                 wave-
>>>>>>>>                 freq 10e6 --gain 100
>>>>>>>>                 on the first USRP N310 (x=10) and then on the other (x=20). There
>>>>>>>>                 is
>>>>>>>>                 an offset of 1200Hz between the peaks of the sinusoids between
>>>>>>>>                 the
>>>>>>>>                 two measurements.
>>>>>>>>                 Using an external LO didn't change anything either. Unless I need
>>>>>>>>                 to
>>>>>>>>                 provide any other arguments in that case?
>>>>>>>>                 I also tried to do a test where I use both USRPs simultaneously
>>>>>>>>                 ./tx_waveforms --args
>>>>>>>>                 "addr0=192.168.10.2,addr1=192.168.20.2,time_src=external,clock_sr
>>>>>>>>                 c=ex
>>>>>>>>                 ternal,master_clock_rate=122.88e6" --rate 122.88e6 --freq 3.51e6
>>>>>>>>                 --
>>>>>>>>                 wave-type SINE --wave-freq 10e6 --gain 100--channels "0,4"
>>>>>>>>                 but unfortunately that does not work at all at my testbench
>>>>>>>>                 (program
>>>>>>>>                 hangs and no signal transmitted).
>>>>>>>>                 My UHD version is 3.13.0.2 (UHD_3.13.0.HEAD-0-g0ddc19e5)
>>>>>>>>                 Any help appreciated.
>>>>>>>>                 Thanks!
>>>>>>>>                 Florian.
>>>>>>>>
>>>>>>>>>                 On 04/12/2018 21:29, Florian Kaltenberger via USRP-users wrote:
>>>>>>>>>                 Hi Marcus and Robin,
>>>>>>>>>                 thanks for your answers, this is helpful information. I should
>>>>>>>>>                 add,
>>>>>>>>>                 that I actually tried the synchronization with an octoclock
>>>>>>>>>                 (10MHz
>>>>>>>>>                 + PPS), but it did not give me the expected results, i.e., I
>>>>>>>>>                 saw
>>>>>>>>>                 some residual frequency offsets. But maybe I screwed up at some
>>>>>>>>>                 point. Let me do some more measurements and get back to you on
>>>>>>>>>                 this.
>>>>>>>>>                 Florian.
>>>>>>>>>
>>>>>>>>>>                 On 04/12/2018 18:57, Marcus D. Leech via USRP-users wrote:
>>>>>>>>>>                 On 12/04/2018 10:14 AM, Florian Kaltenberger via USRP-users
>>>>>>>>>>                 wrote:
>>>>>>>>>>>                 Hi there,
>>>>>>>>>>>                 I just discovered that in addition to the external 10MHz
>>>>>>>>>>>                 reference in, the USRP N310 also has external local
>>>>>>>>>>>                 oscilator
>>>>>>>>>>>                 inputs, one for each daughterboard and each TX/RX. So does
>>>>>>>>>>>                 that
>>>>>>>>>>>                 mean that in order to synchronize multiple N310 in
>>>>>>>>>>>                 frequency,
>>>>>>>>>>>                 phase, and time, it is no longer sufficient to use an
>>>>>>>>>>>                 octoclock
>>>>>>>>>>>                 to provide a 10MHz reference and PPS? If so, at what
>>>>>>>>>>>                 frequency
>>>>>>>>>>>                 do you have to drive the external LOs and at what power?
>>>>>>>>>>>                 Florian.
>>>>>>>>>>>
>>>>>>>>>>                 In addition to what Robin posted, I'll observe that the
>>>>>>>>>>                 external
>>>>>>>>>>                 LO port is an *additional feature* of this device.
>>>>>>>>>>
>>>>>>>>>>                 You should still be able to use the external 10MHz and 1PPS
>>>>>>>>>>                 ports
>>>>>>>>>>                 the same way you would with a B210 or E310, since the AD9371
>>>>>>>>>>                   front-end chip is similar to the AD9361 chip used in the
>>>>>>>>>>                 B210
>>>>>>>>>>                 and E310.
>>>>>>>>>>
>>>>>>>>>>                 The thing about synchronizing multiple independent PLL
>>>>>>>>>>                 synthesizers, though, compared to a strictly-shared-LO, is
>>>>>>>>>>                 that
>>>>>>>>>>                 the former will
>>>>>>>>>>                   experience both phase ambiguities, and have a higher mutual
>>>>>>>>>>                 phase-noise than the latter, which is why you might decide to
>>>>>>>>>>                 choose
>>>>>>>>>>                   the latter.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>                 _______________________________________________
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