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[Discuss-gnuradio] MICA2 reception at ISM 433MHz

From: Luis Simoes
Subject: [Discuss-gnuradio] MICA2 reception at ISM 433MHz
Date: Wed, 26 Apr 2006 17:57:30 +0200
User-agent: KMail/1.8

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,


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