The pi-top  Hub controls the power supplied to the Raspberry Pi to communicate with the screen and battery. It's also the interface of all pi-top accessories such as the pi-topPROTO+ and pi-topSPEAKER.
The pi-top  Hub talks to the Rasberry Pi via I2C and is at address 0x10
Modular Rail pinout
|Name||Function||Voltage (Volts)||Max Current (Amps)||Description|
|V_IN||Power Out||18||0.5||Input to system voltage. Can be used to power 5V and 3V3|
|5V||Power Out||5||0.5||Fed by V_IN. Feeds into 3V3. Also supplies Raspberry Pi 5V. Available when system is off but will turn off when battery is below 2%|
|3V3_PRST||Power Out||3.3||0.1||Fed from V_IN|
|3V3||Power Out||3.3||0.5||Fed from 5V. Feeds into 1V2|
If the hub doesn’t align properly with the Raspberry Pi ports, simply turn the adjustment screws to raise or lower the HDMI connector. Turning clockwise will lower it, anti-clockwise will raise it.
Check out the Getting Started Guide for more information.