Simple Frame Detection

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