RFID Grid Demo - Multiplexing 4 Readers (Proof of Concept)
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- Опубликовано: 20 сен 2024
- I'm multiplexing 4 RobotDyn MFRC522 RFID readers using 16-1 Analog Multiplexers on the SPI bus. With another 4 pins dedicated to the Chip Select. This is simply a proof of concept demonstration as part of my ECED4900 - Senior Year Project course at Dalhousie University.
Do you think it is possible to build the same grid, but 10x10 instead of 4x1? Also, are there smaller RFID antennas out there that could feed in one receiver?
Hi, I have a similar project with a 3x3 matrix to tick toe, I bought several Robotdyn sensors but have not been able to get them to work properly. Could you show me the circuit diagram in arduino or show me some of the code? The examples I found on the net did not work. Please, I would appreciate your help!
github.com/markdhooper/rfgrid-ECED4900/tree/master/docs/cctSchematics
github.com/markdhooper/rfgrid-ECED4900/blob/master/arduino/rtc(current)/rfgridComms/rfgridComms.ino
The ardiuno code is using a specific communication protocol (serial between the pc and arduino) that is taylor made for rfgrid, but essentially the spi communication between the readers and the arduino only uses one spi object, and I am using an 8 bit address to select which reader to talk to. The top 4 bits are the board address, and the bottom 4 are the reader address. The arduino shield uses a line decoder to route the spi lines using the top 4 address bits to the correct board, and each board has 16 readers, and another line decoder stage that routes the spi lines again to the desired reader. If you only have 9 readers, you could probably get by by using one pin for each reader's chip select. Since I wanted to be able to use up to 256 possible readers, I had to use the address approach. I was able to get the readers switching using a shift register in the beginning, when I had 4 readers. That worked fine, but before you switch readers, make sure you send an ANTENNA OFF signal to the reader before switching to a new one, or the readers will interfere with each other.
Oh, I should mention that this code is from a different hardware configuration than the one seen in this video.
What happens if you place 2 RFID on the same reader?
It will only detect one, usually the one on the top. But it's not a very reliable read, and depends on the orientation of the coil(s) in the tag. The card almost always outperforms the fob with the readers that I used.
I had the same problem with normal RFID-RC522 sensors, but I bought from RobotDyn brand and they are supposed to work for I2C