is there an example code of CN531 for Arduino?
Especially for Uno, CN0531 could be a good extension.
We don't have support for Arduino Uno, only for ADICUP3029. But with what is already provided, it should be easy to adapt for Uno.
You can also use RPI if you connect the PMOD correctly to SPI0: https://github.com/analogdevicesinc/linux/blob/rpi-5.4.y/arch/arm/boot/dts/overlays/rpi-ad5791-overlay.dts#L33