04 · Getting started with STD

The first reads from an STD module over I²C and over Modbus RTU. Register addresses are I²C 16-bit pointers; the Modbus addresses are given in brackets. Full flows are in the sequences reference.

0. Select the transport

Set the 3-position interface mode switch before power-up: Modbus RTU (saved serial settings), Modbus default (Modbus RTU at 9600 8N1, unit id 1) or I²C. The switch is read only at start-up, so a change applies after a restart. See Hardware.

1. Identify the module

Read 12 bytes at 0x0000 in one transaction (I²C: write the 16-bit pointer 0x0000, then read 12 bytes):

The exact byte layout is in Identity & discovery. Decide what the module can do from N_VOLTAGE, N_CURRENT and the CAPABILITIES bits — never from hardcoded variant codes.

Then read the unique UID (0x00F4, 12 bytes) for your database and the firmware version FW_VER (0x0114, u32): the high word and the low word in decimal give the version, for example 0x0001007E = STD firmware 1.126.

2. Wait for live data

After power-up allow about one second: WIN_SEQ (0x0016) must be non-zero and stepping, and STATUS bit 1 (sensor ok) set. See boot readiness.

3. First reads (I²C)

Read the realtime blocks in one transaction each (up to 128 bytes, coherent):

• voltage channel v: base 0x0200 + v·0x20 — RMS voltage;
• current channel c: base 0x1000 + c·0x40 — current, P, Q, S, PF;
• totals: 0x0300 + k·0x40 — k = 0 grand total, k = 1..3 per phase;
• frequency FREQ (0x0010, cHz).

The complete block layouts are in the register map. Values are fixed-scale integers: voltage in mV, current in µA, power in mW / mvar / mVA.

4. First reads (Modbus RTU)

Defaults: unit 1, 9600 8N1. The discovery block is readable as input registers from 0x6000 (magic, map version, capabilities, channel counts, variant, UID). Live values are in the native profile (input 0x6000+) or, for an inverter or SCADA that reads Eastron-type meter points, in the SDM630-compatible float profile (input 0x0000: voltage, current and power per phase, total power, frequency, import and export energy). Details: Modbus transport.

5. Set the time (optional but recommended)

Modules keep no battery clock. Counters accumulate without it; hourly history records are written only after the time is set. Set the time by having the master write the epoch to TIME_SET (0x08C0) and issues command 0x06. Do it at discovery and whenever STATUS bit 4 (time valid) reads 0 after a restart.

In the client libraries

The libraries do all of the above in begin() and expose the same read calls on STD and BASIC modules; see Examples. On a module with snapshot banks and energy counters use Arduino 1.6.2 or later or ESP-IDF 1.7.3 or later.