1 Topic by jcgm (edited by jcgm 2014-04-26 07:40:33)

  • jcgm
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  • Registered: 2014-04-26
  • Posts: 2

Topic: Reading larger data blocks (> 255 bytes) from B tag

Is it possible to read or write greater than 255 bytes through libnfc?


I have a scl3711 usb dongle and a passive tag (actually a TI device which is Tag Type 4, ISO14443 B tag).

I can use the read binary and write binary commands to read and write up to around 250 bytes but if I extend this I get various errors and sometimes a driver seg fault.

Note that to read greater than 255 I send the Tag 4 spec command to read greater than 255, which uses three bytes to speciy the length.

Has anyone had any success doing this? 

Note I can loop over the read or write binary commands, updating the offset each time and successfully access the entire tag sram of 3000 bytes.  This is slow though as the response from the tag takes some time during each loop.

I suspected that the 255 limit is due to the frame size but I would have assumed the driver would take care of this?

  • Registered: 2014-10-08
  • Posts: 2

Re: Reading larger data blocks (> 255 bytes) from B tag

Hello! As I mentioned here: libnfc.org/community/post/5389/#p5389 (I can't post links)
I'm looking for some references/examples on how to read card datas on ISO144434B
Actually I can read the UID and open target, can you kindly tell me the function that you use in order to read/write binaries on card's blocks? Thanks:-)