# Simple Frame Detection

**URL:** <https://www.ruby-forum.com/t/simple-frame-detection/234111>\
**Category:** GNU Radio\
**Created:** [February 7, 2015, 2:25am UTC](https://www.ruby-forum.com/t/simple-frame-detection/234111 "2015-02-07T02:25:31Z")\
**Posts on this page:** 1\
**Page:** 1

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**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:** [February 7, 2015, 2:25am UTC](https://www.ruby-forum.com/t/simple-frame-detection/234111/1 "2015-02-07T02:25:31Z")

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I have been searching for a simple frame detection scheme for GNURadio  
for a while, but everything I’ve found either doesn’t work or it is more  
complicated than I expected.

What I needed was a block that would be searching for a predetermined  
sequence used by the transmitter. While it doesn’t find this sequence,  
it should give no output. Once it is found, it should output everything  
that came after the sequence and discard the rest as “garbage”.

I tried using the simple framer and simple correlator. I created a  
simple example that just took a random source, created a frame,  
converted it to float, added some delay and then the correlator would  
try to find the sequence. But this didn’t work. I got a constant zero  
signal as output. The documentation on these blocks is really poor and I  
couldn’t find any good example to clarify its usage.

On the other hand, I found plenty of examples of the header/payload  
demux. But it seems more complicated than what I need. I don’t quite  
understand the tags and streams portion of GNURadio and I am not sure on  
what I should use as header data.

I will attach my project to this topic. I wish I could add this kind of  
scheme next to the file source and sink.

Thanks in advance,  
Dan Franch