How many RC-522 RFID reader/writers can I use on a single Arduino (e.g. the Uno)? Like, is the only limit the amount of physical inputs on any Arduino or does the system become unstable with too many?
I have seen 4 at the most being used at once in examples such as this project:
Hackaday RFID project
Also, should I use a bi-directional convertor for each connected RFID reader/writer or will they function fine without them?
Thanks in advance for any advice