HUB is one of the six Units in M5GO, allowed to buy separately. This Unit is used for GROVE port expansion. Notice: HUB is just a hardware expander, if you are looking for hardware and software(standard protocol) expander like I2C, Single-bus, please check PaHUB or PbHUB. If you connected two I2C slave devices onto HUB that share the same address, you will have problem getting I2C data from both.