This HAT is pretty simple but its worth going thru what pins are used for what!

The Ultimate GPS uses the following GPIO pins: TXD, RXD, #4 and EEDATA/EECLK

Serial Console Pins

The Raspberry Pi has only one serial port, and you do need serial to chat to a GPS so we will take over the RXD and TXD pins.

PPS Pin

GPS's can output a 'pulse per second' for synchronizing the time. We have a breakout for this and a closed jumper that connects it to GPIO#4 - if you do not need PPS and want to  use #4 for something else, just cut the little connection on the PPS PCB line.

HAT EEPROM

EEDATA/EECLK are connected to a 24C32 EEPROM that contains the name and maker of this HAT (it's not used by the Pi Kernel just yet)