One way to understand this is to think of a teacher trying to take attendance in a room containing a lot of students, but with no list of the children's names. The instructor might announce, "If your last name begins with the letter A, stand up." If five children stand up, he or she might say, "If your last name starts with AA, remain standing. If not, sit down." That might leave one child to communicate with. Then the teacher can say, "If your last name starts with AB, please stand up." And so on.
RFID systems have a variety of different means of doing this as rapidly as possible. But essentially, they all come down to the same processes of polling the tags, and narrowing down the requests until the reader can communicate with one tag at a time. It happens very quickly, so it appears you are reading 50 or so tags at the same time, when, in fact, the reader is communicating with only one tag in any given interval.
I have seen the firm read 100 tags on documents stacked one on top of another. I have also witnessed NXP Semiconductors interrogate tags on 90 drug vials without a problem.
How does one get a decisive answer from Adafruit re this subject.
Does the chip / board(s) / library support 'simultaneously' reading from more than two tags?
You can only physically read max two cards. The spec and HW is defined tha way.
dennisma wrote:There is no RFID limitation in the spec that I have ever heard of. On the contrary there are readers that can read tens/hundred RFID tags simultaneously.
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