System Architecture

Status: DRAFT

                EMS Backend / Cloud
                        |
                NATS over secure link
                        |
                     VPN path
                        |
              outbound connections
                        |
              +---------v---------+
              |    EMS Gateway    |
              | Raspberry Pi Zero |
              |                   |
              | Supervisor        |
              | NATS client       |
              | VPN client        |
              | Modbus drivers    |
              +---------+---------+
                        |
                     RS485
                        |
                 +------v------+
                 |   Inverter  |
                 +-------------+

Backend identity model

The backend stores a device record associated with:

• customer e-mail/account
• Raspberry Pi serial number
• device-specific security identity (TODO: document exact NATS identity and VPN credential identifiers)

The Raspberry Pi serial number is an inventory identifier. It must not be treated as a secret or as sufficient proof of device identity.

Control model

Cloud commands should be semantic operations, for example:

• SetSchedule
• SetOperatingMode
• StartGridCharge
• StopGridCharge
• EnableExport
• DisableExport

The gateway validates the command before translating it into inverter-specific Modbus operations.