GPIO Socket (J15)
The GPIO socket, marked J15 on the circuit board, allows access to several different power and data lines:
- I2C serial protocol
- Spare pins on the FPGA
- 5v, 3.3v and GND
The UART is also used for the ESP Wi-fi module, and can't be used from the GPIO without removing the ESP module. I2C is also used to communicate with the real time clock module.
The GPIO is not populated and requires a socket to be installed. Pull up/down resisters may be required for some pins to limit current.