Delay of Synchronization by using PPS

GNU Radio
1

hi guys,
Im using a USRP-N and a USRP2 to send a Square Signal to another USRP2
for proving Synchronization by using PPS.

after execute a get following message:

linux; GNU C++ version 4.6.3; Boost_104800; UHD_003.007.000-1-stable

Using Volk machine: sse4_1_32
– 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)
– 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)
– 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)

It seems to work well,but when i look into the scope sink i found a
pretty randomed delay between 2 Transmitters.
it looks like this: --˜˜˜––˜˜˜––˜˜˜––˜˜˜–___
after restart it would look like
this:-˜˜˜˜--˜˜˜˜--˜˜˜˜--˜˜˜˜-_

I tried set a delay-block to compensate,but i realize coz of random i
cant find a constant delay.
did I do something wrong or there is a certain way to “tell” the 2
Transmitters send Signal in the same time?

Yao

2

Hi ? ?,

I don’t really understand your timing diagram (~-_- style), could you
explain them in more detail?

Greetings,
Marcus

3

sry, i think a screenshot sould be much better.

if attachments doesnt work,here is the link from google drive :
https://drive.google.com/file/d/0B_ix7k8ahVJ3MDItTlNTNHJRNWM/edit?usp=sharing

when i executed my flow graph i got left timing diagram,then i killed it
and executed again,i got right timing diagram.
it looks like one signal “moved” to right side a bit.thats the delay i
was talking about.

even the left one looks odd,what i expect sould be a 1000Hz Square,well
at least sould look like a Square.

Yao

Date: Thu, 17 Jul 2014 19:22:58 +0200
From: [email protected]
To: [email protected]
Subject: Re: [Discuss-gnuradio] delay of Synchronization by using PPS

Hi 闷 郁,



I don't really understand your timing diagram (~-_- style), could
you explain them in more detail?



Greetings,

Marcus



On 17.07.2014 18:32, 闷 郁 wrote:



  hi guys,

Im using a USRP-N and a USRP2 to send a Square Signal to another USRP2
for proving Synchronization by using PPS.

after execute a get following message:

linux; GNU C++ version 4.6.3; Boost_104800; UHD_003.007.000-1-stable

Using Volk machine: sse4_1_32
– 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)
– 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)
– 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)

It seems to work well,but when i look into the scope sink i found a
pretty randomed delay between 2 Transmitters.
it looks like this: --˜˜˜––˜˜˜––˜˜˜––˜˜˜–
after restart it would look like
this:-˜˜˜˜--˜˜˜˜--˜˜˜˜--˜˜˜˜-

I tried set a delay-block to compensate,but i realize coz of random i
cant find a constant delay.
did I do something wrong or there is a certain way to “tell” the 2
Transmitters send Signal in the same time?

Yao

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