I was working with an RFID RC522 using a Mega2560 Board. The pins were directly connected to the board. I am aware that the 5V pins should be dropped for the RFID. This is not necessarily a question about the connection. My question is - the RFID ONLY worked on my board when the 3.3V and the GND pins were disconnected. The only pins that were connected were the SPI pins (PICO/POCI, SDA/SS) and RST. Four pins in total. IRQ, 3.3V and GND were all disconnected. This setup was the only way I could get the RFID to work.
Bad electronics wiring aside - does anyone know the internal composition that allowed the RFID to work in this way without power? I read a post that since the RFID is not fault tolerant, the SPI pins could "pull up" the 3.3V line so it would get some residual from the pins, but the ground was still not connected.
Any assistance in understanding the makeup here would be appreciated. Thanks!
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