While the Raspberry Pi has very good support for an I2C bus, a lot of very cool chips – including the in system programmer for just about every ATtiny and ATmega microcontroller – use an SPI bus.

More often than not, an IoT master device uses the SPI (serial peripheral interface) and I 2 C (inter-integrated circuit) protocols to exchange data with EEPROMs or sensors that are operating in slave ...

There’s also a Python library (basically a set of commands you can use to control the robot) available to go alongside the HAT, which will let you write software to control the robot parts you’ve got ...