RS485-HAT is a TTL to RS485 converter for M5StickC. Among M5stack products we have 5 items that include TTL to RS485, they are RS485 unit, RS485 HAT, PLC, LAN, BASE26 they have different input voltage, vary from 5V - 12V. In this RS485-HAT, it consists of a 485 automatic transceiver circuit and a DC-DC buck circuit which can drop an input 12V to 5V. RS485 is a standard defining the electrical characteristics of drivers and receivers for use in serial communications systems, widely used in the industrial field. multi point systems are supported. It is used to convert the TTL standard to the RS485 standard. If the outside serial device is RS485 standard, you can attach this hat on top of stickc, therefore, to implement the communication with RS485 device by TTL protocol.