RFID reader (WPI405) example code not working

Hi all,
Just bought this card with two RFID tags and connected it to a brand new Pi Zero 2 w with a new install of PiOS (64). Information about how to use the card is a bit sparse and I tried the instructions here:
How to setup a Raspberry Pi RFID RC522 Chip - Pi My Life Up
without success. Just nothing either on the card (not even a LED saying it has power) no errors from the python code, and no response, read or write, from either of the two provided RFID tags.

The card in the instructions is the previous version and has an SDA pin, where as this newer version has a NSS pin. I guessed that should be connected to gpio24 on the assumption it is a naming convention. Alternatively, could it be that I need to use 32bit PiOS?

Any advice? Happy to wade through data sheets but if I don’t need to …

That’s a bit confusing? SDA GPIO 2, is i2c, and it is using SPI? Unless I’m missing something? The user manual says NSS (= SDA)
vma405_a4v03.pdf (shopify.com)

That would explain the renaming. The RFID card (old version) has an SDA pin (labelled “SDA”) that the instructions say to connect to the pi’s pin 24 (not SDA). The new version of the RFID card does not have an SDA pin but does have a NSS pin.

Keep in mind that (physical) pin 24 is GPIO 8 (BCM numbering) And that is SPI Chip Select 0. Make sure your on Pin 24 not GPIO 24.

Okay my fault; had swapped MISO and MOSI lines for some reason (it was a late one last night…). So can confirm that the WPI405 works with the instructions at

and that, where the site mentions SDA, it is now the NSS pin.


Nice to hear you got it working. Mistakes like that are easy to do. I’ve made my fair share of them.