The two boards are connected with an RS485 link on which data are exchanged through a proprietary protocol.
With regard to the The gatewayis powered by an embedded Linux distribution, on which was tailored for such applications. On the legacy machine side, it the gateway acts as a traffic sniffer. It is connected to the RS485 link and "eavesdrops" all the traffic flowing through this channel. As it is aware of the protocol used, it can parse the exchange packets and extract data from them. On the cloud side, the gateway uploads to the NoSQL database every extracted piece of data along with an associated timestamp.
It is worth remembering that the '''extraction of data to be uploaded to the cloud is a non-intrusive process''': to implement this solution, '''no hardware/software modifications of the legacy machine were required'''.