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reading from thread Bewator, http://www.proxmark.org/forum/post.php?fid=16976, I came across the usage of lf config, where a threshold is activated in order to improve lf snoop activity.
when I only changed the threshold 240 this command was sent to serial interface
lf config L b 8 d 1 a 1 t 240
because
L is default,
bit rate /sample is 8 by default
decimal d is 1 by default
average a is 1 by default
Questions:
1/ If I write only "lf config t 240" system should be configured equivalent to "lf config L b 8 d 1 a 1 t 240"? (yes, I think so)
2/ if I write "lf config H t 240" system is config equivalent to do it for 134 kHz, with threshold 240, for how long, each time
system get stuck, if we have to press PM button, or if reset the COM, or if restart GUI the config setting will need to be set again, is it correct?
3/ I understand a good reading is when graph displays <-50 and >50 so why is good threshold level at 240? or because like we see normal good graph range -120 to 120, that made 240 and is the range snoop is intended to be active?
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1. Only if your config is still at default settings.
2. The config is set in the pm3 firmware until the pm3 is reset. Client doesn't matter. If you set a 240 threshold then your tag had better be strong enough to max out and get clipped in the graph window. If you do this with H option you had better have strong 134 kHz tags or it will never reach that graph value. (And thus never return.)
3. 240 was a specific case for a specific snoop when we already knew the values the reader/card returned... Not to be used for all.
The current threshold value is in arm signal (0 to 255) not graph values(-128 to 128). Also it only thresholds on the high signal not the low peaks.
However in my next pull I adjusted that value so this will change to match the graph and be set by values between 0 and 128 and it will be triggered if the high > threshold or if low is < -threshold.
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Thanks for the clarification Marshmellow.
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