01 · Define the scope
List M1 three-phase circuits, M4 single-phase branches, locations, versions, required measurements, sampling intervals and target systems. Identify overlapping supply and branch boundaries.
02 · Select the protocol path
For raw TCP, the host constructs and decodes meter messages. Modbus TCP function 03/04 requires a compatible RTU map. A shared RS485 interface does not establish protocol compatibility.
03 · Align data definitions
Agree slave addresses, function codes, address base, types, byte order, scaling, units, timestamps and quality flags. Treat energy counters and instantaneous values separately. Do not turn connection failures into zero readings; define backfill and duplicate handling in software.
04 · Plan polling and networking
Use static IPv4. Raw P1/P2 each allow one connection; Modbus TCP allows one connection and selects one downstream channel. Keep one master per bus and validate capacity against the sampling target.
05 · Deliver a testable interface
Deliver circuit, wiring, network, version and point-map records, sample messages and decoded results, and timeout and disconnection logs. MQTT, HTTP data APIs, BACnet, OPC UA and business reporting belong to the target system or a separate software adapter.
Confirm status reads and control writes separately
AG-2701X currently supports only 03/04 reads through Modbus TCP→RTU. AC-2705X input and output-command states can be read with 04. Relay writes using 05/0F require complete RTU frames over raw TCP, with the host handling CRC, polling and scheduling. The read-only gateway route cannot perform these control writes.
Use one agreed protocol route per channel. Output readback reports the command state; actual load operation requires independent feedback. Include interlocks, permissions, failure states and recovery in acceptance tests.
Review the complete delivery and acceptance checklist
AC-2705X status points and event writes
For status, use function 04 to read two registers from 0x0010: 0x0010 holds the 8-bit output-command bitmap and 0x0011 the 4-bit input bitmap. Check protocol 1.2 and code baseline 0.6.2 against the supplied version.
Event heartbeat, sequence, acknowledgement and UTC setting use 06/10 writes. Include them in the raw RTU route or develop and validate a separate adapter. Start with common 9600 bit/s, 8N1 settings, one master per segment and unique addresses.