[USRP-users] Why do we need 1 PPS and 10 MHz signal to synchronize
Hello Community, Like in the topic, I know that a stable 10 MHz source is needed as a clock signal but why do we need 1 PPS signal? How is it used by the USRP hardware? Can someone explain that to me? Thanks Marcin ___ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
[USRP-users] Re: Why do we need 1 PPS and 10 MHz signal to synchronize
Marcus, Thank you very much for the answer. Does it mean that 1 PPS signal is optional? Can I only provide an external 10 MHz clock without 1 PPS? *Z poważaniem * *Marcin Puchlik* śr., 11 maj 2022 o 14:24 Marcus D. Leech napisał(a): > On 2022-05-11 06:17, Marcin Puchlik wrote: > > Hello Community, > Like in the topic, I know that a stable 10 MHz source is needed as a clock > signal but why do we need 1 PPS signal? How is it used by the USRP > hardware? Can someone explain that to me? > Thanks > Marcin > > ___ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-le...@lists.ettus.com > > 1PPS is used to provide timestamp-clock synchronization across multiple > devices, typically. This is important when your application requires this, > such as in MIMO or > multi-receiver TDOA schemes, etc. > > Basically, when you have multiple devices you use set_time_unknown_pps() > or set_time_next_pps() to signal to all devices in your multi_usrp object > that at the next > 1PPS, to set the timestamp clock to the value given in the the API call. > > This turns out to be useful even in single devices that are "bicameral", > such as B210 and X310, where there are (for historic and architectural > reasons) > TWO timestamp clocks. Use the 1PPS synchronization primitives causes > the internal timestamp clocks to become synchronized. > > > ___ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-le...@lists.ettus.com > ___ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
[USRP-users] Re: Why do we need 1 PPS and 10 MHz signal to synchronize
Will it be enough to clock USRP from the external 10 MHz signal generator? When I run the flowgraph I cannot see the information that is using the external clock. Here is the output from GNU Radio: [INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100; UHD_3.15.0.HEAD-0-gaea0e2de [INFO] [B200] Detected Device: B200 [INFO] [B200] Operating over USB 2. [INFO] [B200] Initialize CODEC control... [INFO] [B200] Initialize Radio control... [INFO] [B200] Performing register loopback test... [INFO] [B200] Register loopback test passed [INFO] [B200] Setting master clock rate selection to 'automatic'. [INFO] [B200] Asking for clock rate 16.00 MHz... [INFO] [B200] Actually got clock rate 16.00 MHz. [INFO] [B200] Asking for clock rate 51.20 MHz... [INFO] [B200] Actually got clock rate 51.20 MHz. [INFO] [MULTI_USRP] 1) catch time transition at pps edge [INFO] [MULTI_USRP] 2) set times next pps (synchronously) [INFO] [B200] Asking for clock rate 51.20 MHz... [INFO] [B200] OK [INFO] [B200] Asking for clock rate 51.20 MHz... [INFO] [B200] OK [WARNING] [AD936X] Selected Tx sample rate (0.2 MHz) is less than analog frontend filter bandwidth (0.2 MHz). [image: image.png] śr., 11 maj 2022 o 15:24 Marcus D. Leech napisał(a): > On 2022-05-11 09:18, Marcin Puchlik wrote: > > Marcus, > Thank you very much for the answer. Does it mean that 1 PPS signal is > optional? Can I only provide an external 10 MHz clock without 1 PPS? > *Z poważaniem * > *Marcin Puchlik* > > > > > > > > > > *Yes, absolutely. If timestamp synchronization is not important to you, > then you can just provide a 10MHz reference when you want better > frequency accuracy and drift characteristics than are offered by the > on-board clock and/or you want some type of phase-synchronization but > don't care much about mutual phase offsets * > > > > śr., 11 maj 2022 o 14:24 Marcus D. Leech > napisał(a): > >> On 2022-05-11 06:17, Marcin Puchlik wrote: >> >> Hello Community, >> Like in the topic, I know that a stable 10 MHz source is needed as a >> clock signal but why do we need 1 PPS signal? How is it used by the USRP >> hardware? Can someone explain that to me? >> Thanks >> Marcin >> >> ___ >> USRP-users mailing list -- usrp-users@lists.ettus.com >> To unsubscribe send an email to usrp-users-le...@lists.ettus.com >> >> 1PPS is used to provide timestamp-clock synchronization across multiple >> devices, typically. This is important when your application requires this, >> such as in MIMO or >> multi-receiver TDOA schemes, etc. >> >> Basically, when you have multiple devices you use set_time_unknown_pps() >> or set_time_next_pps() to signal to all devices in your multi_usrp object >> that at the next >> 1PPS, to set the timestamp clock to the value given in the the API call. >> >> This turns out to be useful even in single devices that are "bicameral", >> such as B210 and X310, where there are (for historic and architectural >> reasons) >> TWO timestamp clocks. Use the 1PPS synchronization primitives causes >> the internal timestamp clocks to become synchronized. >> >> >> ___ >> USRP-users mailing list -- usrp-users@lists.ettus.com >> To unsubscribe send an email to usrp-users-le...@lists.ettus.com >> > > ___ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
[USRP-users] Re: Why do we need 1 PPS and 10 MHz signal to synchronize
But you know what I observed and what is weird? When I ask for an external source and I intentionally turn off the external generator providing a 10 MHz signal, USRP behaves as if it was still seeing a 10 MHz reference signal at its input. Doesn't matter if the generator is switched on or off - USRP behaves the same way. Because of that I am not sure if USRP is being clocked from an internal or external clock source. Is it the bug in the GNU radio or UHD or am I doing something wrong? How can I get the feedback from the USRP hardware that it was locked to the external clock? Is it even possible? śr., 11 maj 2022 o 16:14 Marcus D. Leech napisał(a): > On 2022-05-11 09:51, Marcin Puchlik wrote: > > Will it be enough to clock USRP from the external 10 MHz signal generator? > When I run the flowgraph I cannot see the information that is using the > external clock. Here is the output from GNU Radio: > [INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100; > UHD_3.15.0.HEAD-0-gaea0e2de > [INFO] [B200] Detected Device: B200 > [INFO] [B200] Operating over USB 2. > [INFO] [B200] Initialize CODEC control... > [INFO] [B200] Initialize Radio control... > [INFO] [B200] Performing register loopback test... > [INFO] [B200] Register loopback test passed > [INFO] [B200] Setting master clock rate selection to 'automatic'. > [INFO] [B200] Asking for clock rate 16.00 MHz... > [INFO] [B200] Actually got clock rate 16.00 MHz. > [INFO] [B200] Asking for clock rate 51.20 MHz... > [INFO] [B200] Actually got clock rate 51.20 MHz. > [INFO] [MULTI_USRP] 1) catch time transition at pps edge > [INFO] [MULTI_USRP] 2) set times next pps (synchronously) > [INFO] [B200] Asking for clock rate 51.20 MHz... > [INFO] [B200] OK > [INFO] [B200] Asking for clock rate 51.20 MHz... > [INFO] [B200] OK > [WARNING] [AD936X] Selected Tx sample rate (0.2 MHz) is less than > analog frontend filter bandwidth (0.2 MHz). > > > [image: image.png] > > Yeah, I don't think it puts out an "i'm locked to the external reference" > message. > > But you've asked for "external" clock source, so you should be good to go, > assuming your external generator meets the requirements. > > > śr., 11 maj 2022 o 15:24 Marcus D. Leech > napisał(a): > >> On 2022-05-11 09:18, Marcin Puchlik wrote: >> >> Marcus, >> Thank you very much for the answer. Does it mean that 1 PPS signal is >> optional? Can I only provide an external 10 MHz clock without 1 PPS? >> *Z poważaniem * >> *Marcin Puchlik* >> >> >> >> >> >> >> >> >> >> *Yes, absolutely. If timestamp synchronization is not important to you, >> then you can just provide a 10MHz reference when you want better >> frequency accuracy and drift characteristics than are offered by the >> on-board clock and/or you want some type of phase-synchronization but >> don't care much about mutual phase offsets * >> >> >> >> śr., 11 maj 2022 o 14:24 Marcus D. Leech >> napisał(a): >> >>> On 2022-05-11 06:17, Marcin Puchlik wrote: >>> >>> Hello Community, >>> Like in the topic, I know that a stable 10 MHz source is needed as a >>> clock signal but why do we need 1 PPS signal? How is it used by the USRP >>> hardware? Can someone explain that to me? >>> Thanks >>> Marcin >>> >>> ___ >>> USRP-users mailing list -- usrp-users@lists.ettus.com >>> To unsubscribe send an email to usrp-users-le...@lists.ettus.com >>> >>> 1PPS is used to provide timestamp-clock synchronization across multiple >>> devices, typically. This is important when your application requires this, >>> such as in MIMO or >>> multi-receiver TDOA schemes, etc. >>> >>> Basically, when you have multiple devices you use set_time_unknown_pps() >>> or set_time_next_pps() to signal to all devices in your multi_usrp object >>> that at the next >>> 1PPS, to set the timestamp clock to the value given in the the API >>> call. >>> >>> This turns out to be useful even in single devices that are "bicameral", >>> such as B210 and X310, where there are (for historic and architectural >>> reasons) >>> TWO timestamp clocks. Use the 1PPS synchronization primitives causes >>> the internal timestamp clocks to become synchronized. >>> >>> >>> ___ >>> USRP-users mailing list -- usrp-users@lists.ettus.com >>> To unsubscribe send an email to usrp-users-le...@lists.ettus.com >>> >> >> > ___ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
[USRP-users] Error while compiling rx_samples_to_udp.cpp
Hi, While compiling this <https://github.com/EttusResearch/uhd/blob/master/host/examples/rx_samples_to_udp.cpp> example I got the error: *Creating the usrp device with: ...[INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100; UHD_4.2.0.0-0ubuntu1~focal1[INFO] [B200] Loading firmware image: /usr/share/uhd/images/usrp_b200_fw.hex...[INFO] [B200] Detected Device: B200[INFO] [B200] Loading FPGA image: /usr/share/uhd/images/usrp_b200_fpga.bin...[INFO] [B200] Operating over USB 2.[INFO] [B200] Detecting internal GPSDO [INFO] [GPS] No GPSDO found[INFO] [B200] Initialize CODEC control...[INFO] [B200] Initialize Radio control...[INFO] [B200] Performing register loopback test... [INFO] [B200] Register loopback test passed[INFO] [B200] Setting master clock rate selection to 'automatic'.[INFO] [B200] Asking for clock rate 16.00 MHz... [INFO] [B200] Actually got clock rate 16.00 MHz.Error: LookupError: IndexError: multi_usrp::mb_root(140722477363728) - LookupError: IndexError: multi_usrp::mb_root(140722477363728) - path not found* The command I am using is: *g++ samples_to_udp.cpp -o out -luhd -lboost_system -lboost_program_options -lboost_thread* I am asking for your guidance. Best *Marcin Puchlik* ___ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
[USRP-users] Re: Error while compiling rx_samples_to_udp.cpp
Sorry, while running :) wt., 7 cze 2022 o 18:44 Marcin Puchlik napisał(a): > Hi, > While compiling this > <https://github.com/EttusResearch/uhd/blob/master/host/examples/rx_samples_to_udp.cpp> > example > I got the error: > > > > > > > > > > > > > > > > *Creating the usrp device with: ...[INFO] [UHD] linux; GNU C++ version > 9.4.0; Boost_107100; UHD_4.2.0.0-0ubuntu1~focal1[INFO] [B200] Loading > firmware image: /usr/share/uhd/images/usrp_b200_fw.hex...[INFO] [B200] > Detected Device: B200[INFO] [B200] Loading FPGA image: > /usr/share/uhd/images/usrp_b200_fpga.bin...[INFO] [B200] Operating over USB > 2.[INFO] [B200] Detecting internal GPSDO [INFO] [GPS] No GPSDO > found[INFO] [B200] Initialize CODEC control...[INFO] [B200] Initialize > Radio control...[INFO] [B200] Performing register loopback test... [INFO] > [B200] Register loopback test passed[INFO] [B200] Setting master clock rate > selection to 'automatic'.[INFO] [B200] Asking for clock rate 16.00 > MHz... [INFO] [B200] Actually got clock rate 16.00 MHz.Error: > LookupError: IndexError: multi_usrp::mb_root(140722477363728) - > LookupError: IndexError: multi_usrp::mb_root(140722477363728) - path not > found* > > The command I am using is: *g++ samples_to_udp.cpp -o out -luhd > -lboost_system -lboost_program_options -lboost_thread* > > I am asking for your guidance. > Best > *Marcin Puchlik* > ___ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
