From the Next Thing Co blog:
It’s also a testament to the open source community, readily available data sheets and manufacturing houses, and the tenacity to teach yourself engineering. Groguard, like many of us, is self-taught and pursuing his passion for making through custom projects.
After 4 revisions of the board, Groguard had the design where he wanted it. The custom OSH Park PCB at the heart of Groboy routes signal lines from the 2.8″ TFT display, headphones jack, internal 2500mAh LiPo battery (he estimates 3-5 hours of battery life, though he’s not rigorously tested it), and the PCA9555 I2C GPIO expander, which manages inputs from the 11 onboard buttons, to the respective input and output pins on C.H.I.P. Pro.