Can not deactive SPI slaves's chip select

Projects Networking, Protocols, and Devices
2

The MFRC522 functions will set chipSelectPin LOW when they want to talk to the MFRC522 and HIGH when done talking to the MFRC522.

See: Read_MFRC522() and Write_MFRC522()

There is no need for you to do any more that set it HIGH in setup(). The code for the other device will do the same for that device. Just set all chip-select pins to HIGH in setup().