OK so this design isn’t technically a HAT – because it doesn’t have an EEPROM on it. It’s a Powerboost 1000 + USB/Solar charge hat. This will let you plug in a LiIon/LiPoly battery to power a Pi A+ or B+ and then recharge the battery over USB or a 5V DC adapter or even a 6V solar panel such as the ones we have in the shop. It will provide 1A+ of current to the Pi, and has a smart charger that will seamlessly ‘share’ the load between the battery and charger, so it’s great for ‘UPS’ applications. This one’s going to take a while since its pretty complicated! As always, more Hats here.
What’s a PI HAT? Glad you asked!
In a nutshell a HAT is a rectangular board (65x56mm) that has four mounting holes in the (nicely rounded) corners that align with the mounting holes on the B+, has a 40W GPIO header and supports the special autoconfiguration system that allows automatic GPIO setup and driver setup. The automatic configuration is achieved using 2 dedicated pins (ID_SD and ID_SC) on the 40W B+ GPIO header that are reserved for an I2C EEPROM. The EEPROM holds the board manufacturer information, GPIO setup and a thing called a ‘device tree‘ fragment – basically a description of the attached hardware that allows Linux to automatically load the required drivers.