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Hi,
I am developing custom made reader baseing on MFRC531. I have following issue. If I have no card in range I get no response after REQA (0x26), but if card is in range I receive ATQA (0x04 0x00) only every two times. So communication looks like this:
REQA (0x26)
ATQA (0x04 0x00)
REQA (0x26)
no answer
REQA (0x26)
ATQA (0x04 0x00)
REQA (0x26)
no answer
REQA (0x26)
ATQA (0x04 0x00)
REQA (0x26)
no answer
I would expect to receive ATQA every time, extending delay up to few seconds does not change anythink.
Is this my mistake somewhere in firmware or normal behaviour?
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Hey hey,
You should complete (REQA, finish-SELECT) the anti-collision before you can start a new one. You will find more about this process at this website:
http://www.libnfc.org/documentation/examples/nfc-anticol
Cheers,
Roel
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You should complete (REQA, finish-SELECT) the anti-collision before you can start a new one.
Thanks roel, this may be good suggestion. However is there any word about this in ISO14443 specification? There is only image which showing, when PICC receives REQA enters "Ready" state and then it should not accept more REQA call. So why in my example responds for third REQA? If PICC should not do anything with second REQA why it is responding for third REQA?
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Because it will return to deactivated state when an incorrect frame/message is received during the anti-collision. This is not really the same as HALTED, because it then only respond to WUPA commands.
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This makes sense. Maybe I am inventing the problem, but I will ask, but what if after anticollison specific card is selected (all other cards inactive) and during Mifare authentication or after in encrypted session there will appear REQA or WUPA command in first byte? Does other cards will interprete this like a valid command, responds and generate interferences?
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all the cards will try to anticollision (excluding selected one).
but.... some card will got into strange state and will answer only to second REQA\WUPA, some of cards will go to iso 14443-4(jcop)
so....
the best way to do anticollision
1. field off
2 sleep
3 field on
4 sleep for mifare desfire and plus recovery loop (10ms as I remembered)
5 anticollision
6 auth, read, etc commands)))
7 halt
Last edited by merlok (2012-11-06 17:49:54)
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sorry for this Offtopic post , elektryk, roel, I don't know how to contact you for the group buy http://www.proxmark.org/forum/viewtopic.php?id=1599&p=2
Could you contact me by mail?
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