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Time changes and with it the technology
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Hi,
How do I calculate Frame Waiting Time (FWT), the idle time between transmission of Command and Response from the snoop data? Does ETU in the log (hf 14a list) gives the FWT? If so then is the measurement is in mirco-seconds or milliseconds?
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ETU is the Elementary Time Unit as defined in ISO14443. One ETU is the duration of 1 Bit data transfer - which is 128/13,56MHz = 9,4us.
hf 14a list shows the number of decoded bits, i.e. the duration of the tag response in ETUs.
The time between end of the reader request and start of tag response is the Frame Delay Time (fdt) and is exactly defined (otherwise anticollision wouldn't work). I don't know wether the PM can directly display this time. If you have a data plot then you can determine it as the time between the end of the last pause (carrier off) transmitted by the Reader and the first edge of carrier modulation by the tag.
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Thanks Piwi for an insight into ETU.
I don't know wether the PM can directly display this time.
I found a function "GetDeltaCountUS()" mentioned in armsrc/util.h which might give approximate time between the PCD command received and PICC response received. If I add them to the log, then I can receive it from the client.
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fdt (Frame Delay Time) can now be displayed with hf 14a list f. It is implemented in SVN845. See http://www.proxmark.org/forum/viewtopic … 9721#p9721
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