@ajb2k3 To understand correctly. The M5Stack can use both SPI and I2C (as does the ESP32), however the RFID device I have (and you ordered) only uses I2C, and the code for the library I mentioned only supports SPI. The code you both mentioned supports I2C (Grove Port device). So assuming the tag functions suffice I should use that. Correct or nonsense.

Thanks, both(?). I ran the example and it does seem to work. I also saw that an addition for this library is in the pipeline: https://github.com/miguelbalboa/rfid to also support ESP32.
I can continue building software for the M5Stack hardware with my requirements using, among others, the RFID module, the same ajb2k3 ordered.
Again, thanks!!!

Thanks, this was very helpful. So now the problem is software. As I stated in the first part of the topic: I use software found at https://github.com/miguelbalboa/rfid. Has anyone experience with this in combination with Arduino, M5Stack and the RFID Module with RC522? Or perhaps anyone tells me to use a different IDE and language (I have enough experience with C, but not C++). All suggestions are welcome.

@ajb2k3 Okay, I found the I2C tester and ran it. It shows the addresses 0x68 and 0x75. With the device attached it also shows 0x28. When not attached this disappears. Does this mean the device can be found and the hardware wiring is okay? If so the focus is on a software problem.

Hi there, is there an example somewhere that shows how to use an RFID rc522 i2c module (module like in this post: M5Stick-C can not detected RFID Unit). I have no idea what I need to make it working (libraries and possibly other wiring). I am using the M5Stack with Arduino and installed software from here: https://github.com/miguelbalboa/rfid. Probably not usable because it shows the library might be incompatible.
Someone out there that can give me a kickstart with tutorial example how to use these three together (Arduino, M5Stack and RFID module)?