-2

I have a problem that I need to control two NFC RC522 over a long distance. Now I saw that there is LTC6820 IC that could make my life easier.

However in the datasheet it can be seen that the SPI slaves need an address to indentify, because the CS pin is not switched separately. Is there any way to classify an RC522 with an address and then be able to use it with an Arduino and the MFRC522 library?

Here is a datasheet of the LTC6820: https://www.analog.com/media/en/technical-documentation/data-sheets/LTC6820.pdf

In the datasheet (https://www.nxp.com/docs/en/data-sheet/MFRC522.pdf) of the RC522 there is something about addressing in the bullet point 8.1.2.3, but I don't understand it yet.

I hope someone can tell me about a multidrop connection with the LTC6820 with RC522 slaves.

x.joko.y
  • 3
  • 3

1 Answers1

0

The MFRC522 data sheet 8.1.2.3, refers to using SPI to read and write register addresses within the MFRC522 rather than accessing two MFRC5 on the same SPI bus.

The only way to use SPI for 2 separate devices is to run separate CS lines to the CS pin on each IC.

You can also use I2C slave interface and then MFRC522 can be hardwired to several I2C addresses on one I2C bus. I2C can cover somewhat longer distances than SPI, dependent on clock speed you select and can be extended further using differential I2C https://www.nxp.com/docs/en/data-sheet/PCA9615.pdf

Unfortunately it does not look like the official Arduino MFRC522 library has great I2C support though. https://github.com/makerspaceleiden/rfid#what-works-and-not

QuatCoder
  • 232
  • 1
  • 5