Re: [Discuss-gnuradio] CC1101 GFSK packet decode with variable length

[Alban Meffre]

Hi

i spent the past few weeks studying the gnuradio blocks c++ source codes, the doxygen documentation, and the provided examples (specially packet_tx and packet_rx ones)

and eventually i managed to understand how packetized transmission, tags and messages work

it was easer than i thought initially even if the learning curve is very steep

many thanks for your support

now i plan to learn how to write my own blocks based on the existing, using gr_modtool

i need to write my own custom header formats

bob

Le lun. 31 déc. 2018 à 01:28, Julian Arnold <address@hidden> a écrit :

Hey Bob,

there is plenty of documentation on this topic you can check out under
[1,2].
Especially, the Header Payload Demuxer (HPD) [3] should be worth a look
if you are dealing with packetized variable length data.

Hope those pointer can get you started. If you have further questions
after going through those pages, let me know.

Cheers,
Julian

[1] https://www.gnuradio.org/doc/doxygen/page_packet_data.html
[2] https://www.gnuradio.org/doc/doxygen/page_packet_comms.html
[3]
https://www.gnuradio.org/doc/doxygen/classgr_1_1digital_1_1header__payload__demux.html

On 31.12.18 01:00, Alban Meffre wrote:
> Hi
> I would like to decode a simple GFSK packet
>
> here is the packet structure :
> preamble : AAh x 4
> sync word : D391h
> length byte : 1 byte
> payload : 1 to 64 bytes
> CRC : 2 bytes
>
> TX : arduino + CC1101 module, 2GFSK, 100kbps, excursion 50kHz, carrier
> 433 MHz
> RX : RTLSDR
>
> until now i was able to demodulate the signal and add a "sync" tag using
> the correlate access code.
>
> my goal is to extract the payload and send it to a file or a socket.
> is there a simple way to do that without writing my own block ?
>
> i can't go further, because i do not manage to find the info i need
> i do not know where to start : stream, tagged stream, PDU, messages, etc..
> i do not figure out how to use these tag for variable length. nothing
> clear in the doc
>
> i'd be glad if someone helps me
> best regards
> bob
>
>
>
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>

--

Alban MEFFRE F4GSW