Grumpy_Mike:
No the code will be sent only once when the card is first presented, if the card is held against the reader the card's number is not repeated.Again this was a "special" request I also implemented for a customer, but it is not the way RFID readers normally behave.
The chip that implement most Mifair RFID protocols has "card present" signal inside them and that could be used, but I don't think you have that sort of reader and you certainly can't reprogram the reader's software.
Yeah unfortunately i dont have the Mifare readers. I was advised about maybe restarting the reader every few seconds. would the reader read the card again once restarted? If so can this be done automatically using code? maybe switching off and on the 5v pin