Issues with syncing two USRPs!

GNU Radio
1

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]: <block gr uhd usrp source (1)>]:
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), but I am not
sure
where the commands of synchronizing the device time and channel phase
should be applied?

Thank you.

Best regards,
Khalid

2

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

3

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]: <block gr uhd usrp source (1)>]:
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, [email protected]
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
Sent from the GnuRadio mailing list archive at Nabble.com.

4

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

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
Sent from the GnuRadio mailing list archive at Nabble.com.

5

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

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

6

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.