How to decode packets in Gnuradio

GNU Radio
1

Hi All,

I am new to Gnuradio and trying to decode of bit stream transmitted from
a simple FSK
transmitter like RFM22 without utilizing any OOT block (only using basic
GRC blocks available). Packet format is

8 nibbles (4 octets) PREAMBLE
2 octets SYNC 0x2d, 0xd4
4 octets HEADER: (TO, FROM, ID, FLAGS)
1 octet LENGTH (0 to 255), number of octets in DATA
0 to 255 octets DATA
2 octets CRC computed with CRC16(IBM), computed on HEADER, LENGTH and
DATA

At this point I can demodulate and receive the byte stream ((with LSB
with relevant bit value) without issues. I also passing it though
digital_correlate_access_code_bb and correctly identifying the end of
the sync word. After that I can not figure out what to do to pack the
bits and extract the length and extract the DATA

Can this be done without utilizing OOT blocks. If so can you please give
me some guidance how to do
it.

Thank You

2

If you want to do it without out of tree modules you could do it outside
gnuradio with your own programme. Create a fifo and write out with a
file sink block, then read the data from the fifo in your programme.

Mike

3

Thanks Mike for the reply. In fact my specific question is that, Am I
missing utilizing any readily available block/s to do it function? I
guess based on your answer that its not the case.