[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Discuss-gnuradio] FSK Demodulation trouble

From: Jay Radcliffe
Subject: [Discuss-gnuradio] FSK Demodulation trouble
Date: Tue, 8 Apr 2014 16:35:25 -0600

Hello All, 

I am working on learning gnuradio and getting a grip on demodulating digital communications.  I've been a ham for a long time, and this seems far from my days as a kid running 1200 baud half duplex AFSK.  ;) 

What I have is a toy with a cc1101 chip in it that transmits @ 19.2 k baud, 2-FSK, 16.5 khz deviation. The sync word is the default 0xD3 0x91.   Here is a link to the capture file I am working with: https://dl.dropboxusercontent.com/u/37979208/ping_903.020m_0.400m_20140403_000000z_rtlsdr.cfile

I started out by trying to get Jared Boone's TPMS code to work, https://github.com/jboone/tpms but it doesn't like me or my system at all. (Ubuntu 12.04, gnuradio built with the build-gnuradio script).  I really like his reverse engineering methods that he talked about in the talk he gave at toorcon.  I also like the ability to analyse the captures offline with a CLI interface.  

When I have worked with the GRC, I run the file source through a throttle, then through the quadrature demod block, then to a Scope Sink to try and see the bits on the scope.  I am a little lost on a couple things: 1. I know i need to provide some information about the signal (data rate, deviation, offset) but I don't see any place to add those values.  2. Can I use the squelch block to limit the demodulation to only look at signals above a certain signal strength?  

Ideally, I would love to get a GRC or script that worked on the capture file, then I can have a good example to learn from.  Most of the posts I see from googleing show really incomplete work, or just the final product, without explanation of how to get there (the dreaded "self-documenting code"). 

Any help would be greatly appreciated.  beer is on me if I see you at a conference or swap. 


Jay n8os   

Jay Radcliffe
Twitter: @jradcliffe02
E-Mail: address@hidden
LinkedIn + Resume: http://www.linkedin.com/in/jradcliffe02

reply via email to

[Prev in Thread] Current Thread [Next in Thread]