# Delay of Synchronization by using PPS

**URL:** <https://www.ruby-forum.com/t/delay-of-synchronization-by-using-pps/231025>\
**Category:** GNU Radio\
**Created:** [July 17, 2014, 6:33pm UTC](https://www.ruby-forum.com/t/delay-of-synchronization-by-using-pps/231025 "2014-07-17T18:33:57Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [July 17, 2014, 6:33pm UTC](https://www.ruby-forum.com/t/delay-of-synchronization-by-using-pps/231025/1 "2014-07-17T18:33:57Z")

</div>

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

---

<div class="post-metadata">

**Author:** ![sunkel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/4da419/32.png) [@sunkel](https://www.ruby-forum.com/u/sunkel)\
**Post date:** [July 17, 2014, 7:24pm UTC](https://www.ruby-forum.com/t/delay-of-synchronization-by-using-pps/231025/2 "2014-07-17T19:24:23Z")

</div>

Hi ? ?,

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

Greetings,  
Marcus

---

<div class="post-metadata">

**Author:** ![sunkel](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/4da419/32.png) [@sunkel](https://www.ruby-forum.com/u/sunkel)\
**Post date:** [July 17, 2014, 7:46pm UTC](https://www.ruby-forum.com/t/delay-of-synchronization-by-using-pps/231025/3 "2014-07-17T19:46:30Z")

</div>

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](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: removed\_email\_address@domain.invalid  
To: removed\_email\_address@domain.invalid  
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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```

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