Re: [Discuss-gnuradio] Find a Packet in a bit stream

[Marcus Müller]

Hi Daniel,


On 11/12/2014 11:23 AM, Daniel Batista wrote:
> I need something like the header/payload demux block.
> Can you help my understand how it works?
Well, depends ;) First, I'd point you to the obvious source, the 
documentation for header_payload_demux [1] and especially the "Detailed 
Description" section. That will explain your following quistions:
> The trigger input value can be the starting byte of my packet?
(kind of)
> In header_data input should I insert the expected header?
(no)
> Is it possible to  have a variable length payload?
(yes)
> Instead of defining the length of the frame is it possible to set a byte as the 
> end of my frame?
(no, I think that's the job of the header to define. Packeted 
transmission with end-of-transmission symbols don't really make sense, imho)


header_payload_demux does really what its name promises: Given a sample 
stream and information about packet starts (either via input stream or 
by using trigger_tag_key tags). The packet detection is something you'll 
have to do "upstream" in the flow graph.
I really like to do that, so here I'm pointing you at the official 
documentation for packeted data transmission.

Greetings,
Marcus

> Thank you in advance!
> Daniel

[1] 
http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1header__payload__demux.html
[2] http://gnuradio.org/doc/doxygen/page_packet_data.html
> On Wednesday, November 12, 2014 11:56 AM, Marcus Müller <address@hidden> wrote:
>
>
>
> Hi Daniel,
>
> I think looking at the gr-digital/examples/OFDM example flow graphs will
> help you.
>
> Greetings,
> Marcus
>
>
> On 11/12/2014 10:03 AM, Daniel Batista wrote:
> > Hi,
> > How to tell my receiver to identify a specific packet through a received bit 
> > stream?
> > I transmit a custom packet (with header, payload, crc16).
> > Is there any block in gnuradio that I can use for this purpose?
> > I had a look on "Packet Header parser" and "parser sink" blocks, but I did't 
> > understand how to use them.
> > Any direction or examples will be very helpful for me.
> >
> > Thank you
> > Daniel
> >
> >
> >
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