On the ☒CHIP, the xBUS connector has 10 pins (5 on either side). Of these 10 pins, 4 pins are used for power and 6 pins are used for data transfer.

4 power pins for:

A ground pin GND (0 V)

Provides 3.3 V

V source is a battery or power source (which can be used to supply raw power)

V in is a battery input pin which has not been used but one possibility would be to use it for solar power etc.

6 data pins for:

2 pins used for I2C: one is for SDA and one is for SCL

2 pins used for serial (aka UART): one is for TX and one is for RX

2 pins used for programming: one pin is for programming other core modules and one pins is a reset pin.

link to i2c page

link to serial page