Arduino has shrunk the UNO R4 with the Arduino Nano R4 board equipped with the same 48 MHz Renesas RA4M1 32-bit Arm ...

The RaspPi and the Arduino communicate via UART as [Steve] felt it was a bit simpler than going the SPI or I2C route. The RaspPi GPIO’s run on 3.3v and the ATMEGA328’s like 5v.

I always like projects that bring the Raspberry Pi and Arduino together, however gently. It's what the world needs, a bit more harmony. Check out this little one on GPIO programming on a Raspberry Pi ...