Harvestree Modbus Register Table

← Communication

This document covers only what is needed by a Modbus master in MODBUSSLV mode:

• usable holding-register map,
• data encoding on the wire,
• read/write rules relevant for polling and configuration.

Register map (holding registers)

Encoding and ordering

• Register payload unit is uint16.
• For uint32 / float32, words are ordered LSW first (offset 0), then MSW (offset 1).
• For port windows (0x0100, 0x0140, 0x0180, 0x01C0), the valid offset range is not fixed at 64 registers: it depends on the active measurement type read from 0x000A–0x000D (see Port configured type and dynamic window layout).

Port configured type and dynamic window layout

Each port exposes its active measurement type at 0x000A–0x000D (ports 1–4). The value is a PortType_t code (uint16 in one holding register): the same code used in LoRaWAN uplink metadata (bytes 1–4) and in Toolbox / remote configuration.

Port measurement windows are allocated 64 registers each, but the device exposes only the offsets that match the configured type. Any read beyond that valid range returns illegal address — even inside the 64-register block.

Integrator workflow (dynamic table)

A Modbus master can build its polling map at runtime without hard-coding port wiring:

1. Discover — read 0x000A + (port − 1) for each port (0x000A…0x000D).
2. Resolve layout — look up the code in the table below and open the matching row in Port measurement windows.
3. Poll — read only the valid offsets from that port’s window base (0x0100, 0x0140, 0x0180, 0x01C0). Global address = window base + offset.
4. Reconcile on change — if a port is reconfigured (Toolbox or downlink), the type register and valid offsets update; window bases stay fixed.

Example: port 2 reads 0x000B = 0x0F (WEATHER_A) → valid offsets 0–2 → poll holding 0x0140–0x0142 only.

PortType_t lookup

Codes 0x11, 0x15, and 0x17 are reserved and are not used in production configurations.

Write behavior

• Writable holding registers: 0x0020 (delay before standby — one uint16, seconds) and 0x0021–0x0022 (measurement period — uint32 in milliseconds).
• For the measurement period, write LSW at 0x0021 first, then MSW at 0x0022, to apply the full value.

Port measurement windows (0x0100 / 0x0140 / 0x0180 / 0x01C0)

Each port has a 64-register window. Offset below is relative to that port’s window base (not the global holding address). Which rows apply is determined by the port’s configured type at 0x000A–0x000D — see Port configured type and dynamic window layout.

Register encoding in the window

Physical scaling matches Harvestree LoRaWAN Payload Decoding where the same quantity is transmitted on LoRaWAN. Reads beyond the valid offset range for the active port type return illegal address.

Temperature

Environmental

Voltage

Magnetic field

Current

Industrial analog

Vibration

Dry contact

Document Version: 1.2
Last Updated: 2026-06-02