Forum: GNU Radio MICA2 reception at ISM 433MHz

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Luis Simoes (Guest)
on 2006-04-26 20:03
(Received via mailing list)
Hi all,

I still have problems receiving any data packets from my MICA2 Mote at
ISM
band 433 MHz. I have tuned the usrp to the right frequency and designed
the
channel filters and uspr_fft_py shows me nice results. On the other side
I
changed the gmsk_test.py file in gnuradio-examples to my needs
(manchester
encoding/decoding) and the test worked fine, i.e. Test packets were
manchester encoded, then modulated, I add some noise , demodulating,
manchester decoding, at the end everything was written into a file.
Everything was ok. When I try to combine the usrp_source with its
filters to
the demod chain of the manchester_test file(changed gmsk_test.py) there
is
nothing at the output. I've tried to change some parameters, e.g. the
Threshold of gmsk2_demod_pkt, etc., but without getting any result.
The format of data packet sent by the MICA2 is the following (MAC):

3 bytes preamble
1 byte sync
5 bytes header
29 bytes payload
2 bytes CRC16

the preamble and sync bytes are the access_code of gmsk2 (8 bytes in PHY
layer
after manchester encoding - 0x6666666666669999).
I changed also the gr_packet_sink block to return a constant packet
length.

I don't know what to try out now and hope that someone who has done
something
similar can give me some tips or advises.
I am very grateful for all kind of help,

Luis
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