# Issues of synchronizing two USRP N210s

**URL:** <https://www.ruby-forum.com/t/issues-of-synchronizing-two-usrp-n210s/242175>\
**Category:** GNU Radio\
**Created:** [June 2, 2015, 4:37pm UTC](https://www.ruby-forum.com/t/issues-of-synchronizing-two-usrp-n210s/242175 "2015-06-02T16:37:31Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [June 2, 2015, 4:37pm UTC](https://www.ruby-forum.com/t/issues-of-synchronizing-two-usrp-n210s/242175/1 "2015-06-02T16:37:31Z")

</div>

Hi,

I met the following errors when I try to synchronize two USRP N210s.  
Both  
N210s are fed with 10MHz reference clock and 1 PPS from an OctoClock.  
The  
two N210s are connected via a MIMO cable as well. One N210 is connected  
to  
the Ethernet of a MacbookPro (2010 model) via an Ethernet cable.  
Attached  
is the flow graph and python program used. When I run the top\_block.py,  
I  
met the following errors. According to the previous discussion (  
[http://gnuradio.4.n7.nabble.com/Issues-with-syncing-two-USRPs-td48883.html](http://gnuradio.4.n7.nabble.com/Issues-with-syncing-two-USRPs-td48883.html)),  
it seems that this error is caused by Ethernet connection. However, in  
my  
setup, the N210 is connected to the MacbookPro via Ethernet directly  
without router in the middle. So what could be the potential problem?

RuntimeError: fifo ctrl timed out looking for acks

One more information: I am using GNURadio 3.7.7.1 and UHD 3.8.2.

Pengyu

The complete output of running top\_block.py is:

$ python top\_block.py  
linux; GNU C++ version 4.8.2; Boost\_105400; UHD\_003.008.002-0-ge9d11b35

– Opening a USRP2/N-Series device…  
– Current recv frame size: 1472 bytes  
– Current send frame size: 1472 bytes

UHD Warning:  
Unable to set the thread priority. Performance may be negatively  
affected.  
Please see the general application notes in the manual for  
instructions.  
EnvironmentError: OSError: error in pthread\_setschedparam

## UHD Warning: Unable to set the thread priority. Performance may be negatively affected. Please see the general application notes in the manual for instructions. EnvironmentError: OSError: error in pthread\_setschedparam – 1) catch time transition at pps edge – 2) set times next pps (synchronously) – Successfully tuned to 915.000000 MHz

## – Successfully tuned to 915.000000 MHz

– Opening a USRP2/N-Series device…  
– Current recv frame size: 1472 bytes  
– Current send frame size: 1472 bytes

UHD Warning:  
Unable to set the thread priority. Performance may be negatively  
affected.  
Please see the general application notes in the manual for  
instructions.  
EnvironmentError: OSError: error in pthread\_setschedparam  
– 1) catch time transition at pps edge  
– 2) set times next pps (synchronously)  
– Successfully tuned to 915.000000 MHz