We thought that connecting an Arduino to a Raspberry Pi was overkill ... [Jan] uses the PHP serial class to communicate between the RPi and Arduino (dead link; Internet Archive).

A Raspberry Pi with a camera is nothing new ... You can connect via USB, serial, SPI, or I2C. Internally, the camera processes at 60 frames per second and it can remember seven signatures internally.

and even serve as a serial monitor where you can print messages. If you're more interested in programming with C/C++, there's an 88-page guide you can refer to. The Arduino Nano and Raspberry Pi ...

Don't be fooled by their appearance — there's a world of difference between the tiny Arduino and Raspberry Pi boards ... gained about C++ programming and serial interfaces with Arduino boards ...