The Raspberry Pi is a low cost computer motherboard running on Linux and costs less than 30. Since it's launch millions have been sold to students and hobbyists around the world. The Raspberry Pi has a General Purpose Input Output (GPIO) interface to connect to the outside world. This allows the user to control external devices and make measurements. The Custard Pi range of accessories is designed to plug into the GPIO of the raspberry Pi. The various modules provide a number of useful functions. For example, the Custard Pi 2 has 2 Digital to Analogue (DAC) convertors, 2 Analogue to Digital Convertors (ADC), buffered digital inputs and 4 Open Collector outputs. The Custard Pi 6 has 8 relays which are controlled using the I2C interface bus. If needed, they can be used together to build up a system. This book presents detailed circuit descriptions on the Custard Pi range and provides Python test code. This allows the user to start using them very quickly. Schematics are provided to enable the experienced electronic engineer to modify the cards if required. There is also a chapter on how the various cards can be combined to build up complex systems."