Raspberry Pi is the most popular single board computer among hobbyists and students. In 2014 Raspberry Pi Foundation released a specification for add-on boards called HAT (Hardware Attached on Top). Nowadays we are capable of making our own open source add boards following these specifications. In this presentation, Leon Anavi will share his experience in designing an open source hardware Raspberry Pi HAT and developing open source software for it using only free and open source tools such as KiCAD. Leon has been working on his Raspberry Pi HAT as a hobby project in his spare time for more than a year. In November 2016 his open source Raspberry Pi was successfully crowdfunded through IndieGoGo. Now he will explain the challenges and the common mistakes for a software engineer getting involved in hardware design and manufacturing. The presentation will reveal details about the technical specifications of Raspberry Pi HAT, the life cycle of entirely open source project and will provide getting started guidelines. The presentation is appropriate for anyone interested in open source hardware and open source software development. Previous experience or knowledge about hardware design is NOT required. Attendees can expect details about Raspberry Pi HAT technical specification, embedded Linux software development tips for Raspberry Pi, guidelines for hardware design and low cost manufacturing of prototypes or small volume PCB. This presentation will help software developers, hobbyists and students better understand the value of open source hardware and hopefully it will encourage them to a get a soldering iron and start prototyping add-on boards for their favorite Raspberry Pi. The presentation will be also useful to people interested in the concept of entirely open source projects that integrate open source hardware and software created with free and open source tools.