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Re: [Discuss-gnuradio] Post Binary Slicer question


From: Jay Radcliffe
Subject: Re: [Discuss-gnuradio] Post Binary Slicer question
Date: Wed, 30 Apr 2014 09:22:54 -0600

Maybe I should rephrase: I don't know the entire protocol. I know there is a preamble, and I know the sync word.  I know the packets are not fixed length, I know there is a CRC. This can all be determined from looking at the register settings for the CC1101 chip.  The format of the data portion of transmission I do not know. In order to reverse that I need raw data for analysis. 

That is how I am handling it right now.  I stream the output of the Correlate Access Code to a file sink.  What is in that file though is data, not readable binary stream (or readable hex stream). What I want is tcpdump like output. 

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


On Wed, Apr 30, 2014 at 9:09 AM, John Malsbury <address@hidden> wrote:
Jay,

If you stream the output of the correlate access code to file, and you leave them unpacked, Bit 1 being set will show where the sync word is (I think the bit after).  Of course Bit 0 will be the data.  This assumes you're using correlate access code, and not "correlate access code - tag".  This should allow you to store everything including the preamble. 

Also, if you don't know the protocol, how do you know what the preamble is?

-John


On Tue, Apr 29, 2014 at 1:43 PM, Jay Radcliffe <address@hidden> wrote:
The protocol is unknown at this time.  I need to see the packets to figure some of this out. 

Ideally, I would like to see the entire packet (including the preamble and sync word) to start to work my way to the format of the packets from there.  I am using the power squelch with the gate to limit the captures to just when a signal is over a certain strength. In a perfect world, I would like to have "Binary Slicer" -> "File Sink" where the file contents are the binary stream (10101010101010 not to be confused for a binary file) or hex output (0xAA 0xAA).  I could probably tag the preamble in with the Correlate Access Code? 

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


On Sun, Apr 27, 2014 at 9:28 PM, John Malsbury <address@hidden> wrote:
Jay,

Thanks for the inquiry.  Is there a specific protocol or format you are trying to work with?  Are the frame size fixed in length or variable?  The answers to these questions will dictate whether you can use an existing block or if you will need to write your own.

Writing a block to parse things after the correlate access code block is relatively straight-forward.  If you are using the (tag) version of that block, you simply need to look for the presence of that tag to delineate the start of a frame. 

-John


On Sun, Apr 27, 2014 at 4:27 PM, Jay Radcliffe <address@hidden> wrote:
I have a question about handling data after binary slicing in the demodulation portion of handling a signal. Currently I am taking that data and pushing it through the Correlate Access Code block then into a file sink. This produces a data file.  I didn't know if someone could tell me a block or method that will output the binary stream (or hex stream) to a file or stdout for real-time view of the pack contents. Currently I have some python code that converts that data file into binary/hex which is not idea. 

Thanks,

Jay 


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

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