One of the great things about the Raspberry Pi is the general purpose input output (GPIO) pins. They allow it to interface with other circuits. The Arduino, however, is all about connecting with other stuff, and with analog input and PWM output, it’s better at it than the Pi. But the Pi has more processing power and storage than the Arduino. They can, of course, talk to each other. So an ideal scenario is to harness the power of both of them.
The Pi can be a bit of a beast to tie down though. With connections on every side of the board, and no mounting holes (not in the first release of them anyway), it leaves your working environment quite messy. The fantastic PIBOW case from Pimoroni does a lot to tame the Pi, but not quite enough. However, replacing the bottom layer with a large sheet of perspex gives you a nice mounting board for sticking a breadboard and an Arduino to. Add to that a Pi Cobler from Adafruit to breakout all the GPIO pins and you’ve got the perfect place for prototyping your projects.
I guess now I’ve got no excuse for not getting on with a few projects of my own…