My Notes - mhightower83/CZII_to_MQTT GitHub Wiki

The 16 bit CRC is based on that used for MODBUS.

The serial packet frame is not the same as MODBUS. It has a source address and other additional fields.

Need to look carefully and see what else if anything they borrowed from MODBUS. This could be a good way to fill in some design blanks. Or maybe not. I don't see any commonality in the Function Codes. Maybe look later at minimum frame gaps.

At the moment the only thing common is the use of half-duplex RS485 for the physical layer and the same CRC16 polynomial for the FCS (frame check sequence).