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#1 2014-10-08 19:44:00
- iceman
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- Registered: 2013-04-25
- Posts: 9,538
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LF - Fsk Demodulation
I start a new thread to ask about FSK, since I'm thinking of implement it into the "lf t55xx" commands.
Does someone know how the clockrate work for FSK?
Who did the current implementation for "data fskdemod" ?
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#2 2014-10-08 22:48:18
- marshmellow
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- From: US
- Registered: 2013-06-10
- Posts: 2,302
Re: LF - Fsk Demodulation
I don't know who did data fskdemod (certainly not me)
most common fsk usage for the T55xx is FSK2a RF/50.
i know to manually demod it with the proxmark you can plot the grid at 50 and take high 50 as 1 low 50 as 0.
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#3 2014-10-10 12:59:15
- iceman
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Re: LF - Fsk Demodulation
Even on with my googles skilz, there is very little on fsk demodulation.. plenty of references to PLL and lowpass filters.
Does someone have any kind of information laying around?
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#4 2014-10-13 09:01:22
- Sentinel
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- Registered: 2012-11-26
- Posts: 191
Re: LF - Fsk Demodulation
Using a demodulation scheme. Conclusions ASK and FSK are connected to the microprocessor
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#5 2014-10-13 15:11:59
- gbhuk
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- Registered: 2012-09-20
- Posts: 33
Re: LF - Fsk Demodulation
I found this to be useful: Microchip
Adam Laurie's blog has a nice introduction to the different modulation techniques: adamsblog
Adam's actively involved in developing the RFIdler RFIdler wiki
There's also: proxclone - though unfortunately the person who developed these projects hasn't decided share the code, making the site more interesting than useful, more's the pity.
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#6 2014-10-16 10:44:18
- iceman
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- Registered: 2013-04-25
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Re: LF - Fsk Demodulation
Hm, I notice that FSK-1 vs FSK-2 is very different signals, here I tought that they only had a different fieldclock/framesize R/40 vs r/50. But no.
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#7 2014-10-23 17:42:25
- iceman
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- Registered: 2013-04-25
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Re: LF - Fsk Demodulation
I commited some change to my fork, whichs kind of makes the "lf t55xx" to read a fsk2 configuration..
BINARY
R/40 : 00000001100000000000000000000100000001110000000110000000000000000000010000000111000000011000000000000000000001000000011100
0000011000000000000000000001000000011100000001100000000000000000000100000001110000000110000000000000000000010000000111000000011000
00000000000000000100000
R/50 : 00000110000000000000000100000111000001100000000000000001000001110000011000000000000000010000011100000110000000000000000100
00011100000110000000000000000100000111000001100000000000000001000001110000011000000000000000010000
R/40 ==> C000020380C00002
R/50 ==> 70600010706 <-- which is the configuration 0x00107060 I used on the tag.Offline
#8 2014-10-23 17:44:17
- iceman
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- Registered: 2013-04-25
- Posts: 9,538
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Re: LF - Fsk Demodulation
the downside is that there is no starting-marker so that I can't tell where to start convert to hex. So the output is only binary...
You can see the filtering on the data via the plot. Should be able to use in all other data commands.
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