# Issues with syncing two USRPs! **URL:** \ **Category:** GNU Radio\ **Created:** [June 10, 2014, 10:10pm UTC](https://www.ruby-forum.com/t/issues-with-syncing-two-usrps/230327 "2014-06-10T22:10:18Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 10, 2014, 10:10pm UTC](https://www.ruby-forum.com/t/issues-with-syncing-two-usrps/230327/1 "2014-06-10T22:10:18Z")
Hi, I am a new user of USRP/GNU Radio. I am experimenting with a system comprised of one transmitter and multiple receivers. For now, I have two USRP N200. On the first USRP, I got one LFTX and one LFRX daughter boards. On the other, I got one LFRX daughter board. In my application, it is important that the transmit and receive channels are synchronized (i.e., both device time and channel phase). For this, I am using my own GPS and PPS signals. For the sake of testing, I am feeding the output of LFTX to all the inputs in LFRX (i.e., four receive channels). The output/input type is Complexfloat32. In GRC, when I use a separate USRP source block for each motherboard (i.e., without synchronization), the system is working and I can receive four unsynchronised replicas of my transmitted signal. However, when I a use a single USRP source with two-motherboard and four-channel options, I get the following error message: linux; GNU C++ version 4.8.2; Boost\_105400; UHD\_003.007.001-68-gc4b1f810 – Opening a USRP2/N-Series device… – Current recv frame size: 1472 bytes – Current send frame size: 1472 bytes – Opening a USRP2/N-Series device… – Current recv frame size: 1472 bytes – Current send frame size: 1472 bytes – 1) catch time transition at pps edge – 2) set times next pps (synchronously) Using Volk machine: sse4\_a\_64\_orc _thread[thread-per-block[4]: \]: RuntimeError: fifo ctrl timed out looking for acks_ > > > Done My sample rate is 100e6/128 Hz. In the USRP source I set synch to: UnknownPPS, Mb0/1 clock source and Mb0/1 time source to EXTERNAL. Mb0/1 subdev spec: A:A A:B. I tried to change the WireFormat from AUTOMATIC to ComplexInt16 without any difference. I checked ./test\_pps\_input and I got a ‘success’. I think the issue has to do with the settings for syncing. Any ideas on what causes this problem? BTW, I am also aware of this link ( [http://files.ettus.com/uhd\_docs/manual/html/sync.html](http://files.ettus.com/uhd_docs/manual/html/sync.html)), but I am not sure where the commands of synchronizing the device time and channel phase should be applied? Thank you. Best regards, Khalid ---
**Author:** ![khalid.el-darymli](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6a8cbe/32.png) [@khalid.el-darymli](https://www.ruby-forum.com/u/khalid.el-darymli)\ **Post date:** [June 11, 2014, 3:21pm UTC](https://www.ruby-forum.com/t/issues-with-syncing-two-usrps/230327/2 "2014-06-11T15:21:56Z")
On 10.06.2014 22:09, khalid.el-darymli wrote: > I am a new user of USRP/GNU Radio. I am experimenting with a system > comprised of one transmitter and multiple receivers. For now, I have two > USRP N200. On the first USRP, I got one LFTX and one LFRX daughter > boards. On the other, I got one LFRX daughter board. > > In my application, it is important that the transmit and receive > channels are synchronized (i.e., both device time and channel phase). > For this, I am using my own GPS and PPS signals. What’s the source of these signals? Have you made sure they are generating the right thing (i.e. 10 MHz ref)? Out of curiousity, do you have a MIMO cable and are willing to test that? > For the sake of testing, I am feeding the output of LFTX to all the > inputs in LFRX (i.e., four receive channels). The output/input type is > Complexfloat32. In GRC, when I use a separate USRP source block for > each motherboard (i.e., without synchronization), the system is working > and I can receive four unsynchronised replicas of my transmitted signal. You’re saying you get 2 channels per LFRX, correct? Also, are you attenuating the signal? > – Current recv frame size: 1472 bytes > subdev spec: A:A A:B. I tried to change the WireFormat from AUTOMATIC to > ComplexInt16 without any difference. Just to confirm: You’re setting _both_ clock and time sources to external? M ---
**Author:** ![khalid.el-darymli](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6a8cbe/32.png) [@khalid.el-darymli](https://www.ruby-forum.com/u/khalid.el-darymli)\ **Post date:** [June 14, 2014, 11:49pm UTC](https://www.ruby-forum.com/t/issues-with-syncing-two-usrps/230327/3 "2014-06-14T23:49:19Z")
Hi Martin, This is a follow up on my earlier email. I am still having issues with getting two N200’s to work together. First, please find a short answer to your questions. > > Out of curiousity, do you have a MIMO cable and are willing to test that? > > No, I do not have a MIMO cable. > > You’re saying you get 2 channels per LFRX, correct? Also, are you > > attenuating the signal? > > Yes, I tried both 2 (i.e., A:A, A:B) and 1 (i.e, A:AB). The signal is > > attenuated by a factor of four 'cuz I’m using two T’s each with two > > outputs. > > Just to confirm: You’re setting _both_ clock and time sources to > > external? > > Yes. I initially thought the issue has to do with syncing, but it seems that it is not due to syncing per se (?!) A quick recap. One N200 acts as a single-channel Tx (i.e., A:AB) and a two-channel Rx (i.e., A:A and A:B). The other N200 only acts as a two-channel Rx (i.e., A:A and A:B). I am using two T’s to split my Tx signal into four signals and I am feeding those to the Rx’s. [i.e., my Rx signal is attenuated by a factor of 4]. In GRC, I always use an USRP sink that is properly configured for the Tx AB channel. At the Rx side, for the sake of testing, I tried multiple configurations as follows. First, I only considered one N200 (i.e., a single motherboard) at a time, and I used a source as above. When I do so, _either I apply external sync and clock or not_, I am able to perfectly receive my signal. This test was successful when I fed-in the source with either the two Rx channels from the first or the second N200, separately. Second, I used one single source with two motherboards and four Rx channels. I tested this\* with and without sync/clocking signals\*. In both cases, I get this error message: > Using Volk machine: sse4\_a\_64\_orc > _thread[thread-per-block[4]: \]: > RuntimeError: fifo ctrl timed out looking for acks_ Please note that, despite this message, the GRC program looks as if it is running, and the GUI shows me the output from the scope (i.e., scope is just placed before the USRP Tx sink). However, the output from the scopes after the Rx USRP is null for the four channels. [For Rx’s with a single source, I also tried a single-channel from the two motherboards (i.e., A:AB) without any success]. Checking the system monitor on my computer confirms that one USRP is transmitting all the time while no receive/incoming traffic whatsoever. Besides this, I tried various diagnostics. I thought that the issue may has to do with the Ethernet controller/card on my computer, and that it may be dropping/delaying some packets. Hence, I ‘unmanaged’ the Ethernet connections, and I applied static configuration. I also tried to disable some options in the network driver such as autoneg, adaptive, coalesce, etc., without any success. Please find below some diagnoses that may give some clues on the FIFO ACK error, T-UD2H:~$ sudo ethtool --show-coalesce eth4 Coalesce parameters for eth4: Adaptive RX: off TX: off stats-block-usecs: 0 sample-interval: 0 pkt-rate-low: 0 pkt-rate-high: 0 rx-usecs: 20 rx-frames: 5 rx-usecs-irq: 0 rx-frames-irq: 5 tx-usecs: 72 tx-frames: 53 tx-usecs-irq: 0 tx-frames-irq: 5 rx-usecs-low: 0 rx-frame-low: 0 tx-usecs-low: 0 tx-frame-low: 0 rx-usecs-high: 0 rx-frame-high: 0 tx-usecs-high: 0 tx-frame-high: 0 T-UD2H:/etc/network$ sudo ethtool --show-coalesce eth3 Coalesce parameters for eth3: Adaptive RX: off TX: off stats-block-usecs: 0 sample-interval: 0 pkt-rate-low: 0 pkt-rate-high: 0 rx-usecs: 20 rx-frames: 5 rx-usecs-irq: 0 rx-frames-irq: 5 tx-usecs: 72 tx-frames: 53 tx-usecs-irq: 0 tx-frames-irq: 5 rx-usecs-low: 0 rx-frame-low: 0 tx-usecs-low: 0 tx-frame-low: 0 rx-usecs-high: 0 rx-frame-high: 0 tx-usecs-high: 0 tx-frame-high: 0 T-UD2H:/etc/network$ ifconfig -a eth4 eth4 Link encap:Ethernet HWaddr REMOVED inet addr:192.168.10.1 Bcast:192.168.10.255 Mask:255.255.255.0 inet6 addr: REMOVED\_by\_KE Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:118227 errors:0 dropped:0 overruns:0 frame:0 TX packets:733915 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:8366882 (8.3 MB) TX bytes:930252111 (930.2 MB) Interrupt:19 GA-MA785GMT-UD2H:/etc/network$ ifconfig -a eth3 eth3 Link encap:Ethernet HWaddr REMOVED inet addr:192.168.20.1 Bcast:192.168.20.255 Mask:255.255.255.0 inet6 addr: REMOVED\_by\_KE Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:40807 errors:0 dropped:0 overruns:0 frame:0 TX packets:11811 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3100954 (3.1 MB) TX bytes:1076135 (1.0 MB) Interrupt:18 We also sucessfuly upgraded the firmware for both the USRPs. We noticed that (i.e., also shown form the stickers on the back of each device) one N200 is rev 2.0 and the other is rev 4.0. Could that be the cause of the problem? I will appreciate any help on fixing this issue. Thank you in advance. Khalid On Wed, Jun 11, 2014 at 1:30 PM, [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On 10.06.2014 22:09, khalid.el-darymli wrote: > generating the right thing (i.e. 10 MHz ref)? > attenuating the signal? > > > – Opening a USRP2/N-Series device… > > UnknownPPS, Mb0/1 clock source and Mb0/1 time source to EXTERNAL. Mb0/1 > > problem? > > Khalid – View this message in context: [http://gnuradio.4.n7.nabble.com/Issues-with-syncing-two-USRPs-tp48883p48921.html](http://gnuradio.4.n7.nabble.com/Issues-with-syncing-two-USRPs-tp48883p48921.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![khalid.el-darymli](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6a8cbe/32.png) [@khalid.el-darymli](https://www.ruby-forum.com/u/khalid.el-darymli)\ **Post date:** [June 15, 2014, 4:19am UTC](https://www.ruby-forum.com/t/issues-with-syncing-two-usrps/230327/4 "2014-06-15T04:19:51Z")
Hi Marcus, Thanks for your reply. > Do you know what kind of Ethernet controller is on your ports? Are > they 82579LM by any chance? My Ethernet controller is Broadcom NetXtreme 57XX > **[Support Documents and Downloads](https://www.broadcom.com/support/download-search?pf=Ethernet+Controllers&pg=Ethernet+Connectivity%2C+Switching%2C+and+PHYs)** > > Search technical documentation and downloads including firmware and drivers. [http://www.broadcom.com/support/ethernet\_nic/downloaddrivers.php](http://www.broadcom.com/support/ethernet_nic/downloaddrivers.php) > You _have_ to make certain that Network Manager isn’t trying to > automatically assigned addresses on those cards, since it will try, and > then take them out of service if it doesn’t get a DHCP address > assignment. Yes, I ‘unmanaged’ the two Ethernet connections pertaining to the two N200’s. I can confirm that by going to the ‘network manager’ in Ubuntu where it shows that they are ‘unmanaged’. Then, in the ‘interfaces’ file I define the following: auto eth3 iface eth3 inet static address 192.168.10.1 netmask 255.255.255.0 pre-up ethtool -s eth3 speed 1000 duplex full autoneg off auto eth4 iface eth4 inet static address 192.168.20.1 netmask 255.255.255.0 pre-up ethtool -s eth3 speed 1000 duplex full autoneg off I tried it both with and without the ‘pre-up’ line shown above without any success. If it is a networking issue, is there any thing else you recommend? Can it be an issue of compatibility since one device is N200 Rev 2.0 and the other is N200 Rev 4.0? BTW, I tried to use an external signal generator (not the LFTX installed onboard one of the two N200’s) to feed both the LFRX receivers, and I used one USRP Source in GRC. The four channels worked just fine. The problem is there when only using the LFTX (i.e., installed on one of the N200’s) simultaneously with the _four_ receive channels. Thanks, Khalid – View this message in context: [http://gnuradio.4.n7.nabble.com/Issues-with-syncing-two-USRPs-tp48883p48926.html](http://gnuradio.4.n7.nabble.com/Issues-with-syncing-two-USRPs-tp48883p48926.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![khalid.el-darymli](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6a8cbe/32.png) [@khalid.el-darymli](https://www.ruby-forum.com/u/khalid.el-darymli)\ **Post date:** [June 16, 2014, 2:09am UTC](https://www.ruby-forum.com/t/issues-with-syncing-two-usrps/230327/5 "2014-06-16T02:09:26Z")
Hi Marcus, Thanks for your reply. > Do you know what kind of Ethernet controller is on your ports? Are > they 82579LM by any chance? My Ethernet controller is Broadcom NetXtreme 57XX > **[Support Documents and Downloads](https://www.broadcom.com/support/download-search?pf=Ethernet+Controllers&pg=Ethernet+Connectivity%2C+Switching%2C+and+PHYs)** > > Search technical documentation and downloads including firmware and drivers. > You _have_ to make certain that Network Manager isn’t trying to > automatically assigned addresses on those cards, since it will try, and > then take them out of service if it doesn’t get a DHCP address > assignment. Yes, I ‘unmanaged’ the two Ethernet connections pertaining to the two N200’s. I can confirm that by going to the ‘network manager’ in Ubuntu where it shows that they are ‘unmanaged’. Then, in the ‘interfaces’ file I define the following: auto eth3 iface eth3 inet static address 192.168.10.1 netmask 255.255.255.0 pre-up ethtool -s eth3 speed 1000 duplex full autoneg off auto eth4 iface eth4 inet static address 192.168.20.1 netmask 255.255.255.0 pre-up ethtool -s eth3 speed 1000 duplex full autoneg off I tried it both with and without the ‘pre-up’ line shown above without any success. If it is a networking issue, is there any thing else you recommend? Can it be an issue of compatibility since one device is N200 Rev 2.0 and the other is N200 Rev 4.0? BTW, I tried to use an external signal generator (not the LFTX installed onboard one of the two N200’s) to feed both the LFRX receivers, and I used one USRP Source in GRC. The four channels worked just fine. The problem is there when only using the LFTX (i.e., installed on one of the N200’s) simultaneously with the _four_ receive channels. Thanks, Khalid ---
**Author:** ![khalid.el-darymli](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6a8cbe/32.png) [@khalid.el-darymli](https://www.ruby-forum.com/u/khalid.el-darymli)\ **Post date:** [June 15, 2014, 12:04am UTC](https://www.ruby-forum.com/t/issues-with-syncing-two-usrps/230327/6 "2014-06-15T00:04:09Z")
On 06/14/2014 05:48 PM, eldarymli wrote: > Hi Martin, > > This is a follow up on my earlier email. I am still having issues with > getting two N200’s to work together. > > First, please find a short answer to your questions. > Do you know what kind of Ethernet controller is on your ports? Are > they 82579LM by any chance? You _have_ to make certain that Network Manager isn’t trying to automatically assigned addresses on those cards, since it will try, and then take them out of service if it doesn’t get a DHCP address assignment.