This is a PERMA-PROTO HAT, it’s a PI HAT version of this and it’s part of a new feature we are doing here each day called “HAT A DAY” (sounds like hack-a-day, the site Phil started almost 10 years ago and ladyada is now a judge for in the SPACE contest! This is a HAT a day for a few weeks!)… This is a Raspberry Pi HAT we sent off for prototype PCBs for testing, we’ve sent off many, we’ll post a new HAT A DAY, so stop back soon and see the HATs live on ASK AN ENGINEER each week if we have time during IT’S NOT OUT YET.
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.