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OpenWebNet Diagnostic Protocol

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anotherjulien edited this page Sep 14, 2026 · 6 revisions

Overview

The OpenWebNet Diagnostic Protocol is a family of OpenWebNet messages used by MyHOME Suite to discover, identify, inspect, configure, and program physical devices on a MyHOME/SCS installation.

Diagnostic communication is distinct from the ordinary OpenWebNet messages used to operate the installation.

For example, normal OpenWebNet WHO domains are used to control functions such as lighting, automation, temperature control, or energy management. Diagnostic WHO domains instead provide access to the physical devices and their configuration.

Known or observed Diagnostic WHO domains include:

Diagnostic WHO Domain Status
1001 Automation Documented and observed
1004 Temperature Control / Thermoregulation Documented and observed
1013 Device Diagnostic Documented
1018 Energy Management Observed
1023 Access Control Observed

The detailed diagnostic protocol is only partially covered by public OpenWebNet documentation. The information presented in this wiki therefore combines documented behavior with observations from MyHOME Suite packet captures, controlled configuration experiments, and correlations with the MyHOME Suite catalogue database.

Detailed findings are assigned confidence levels so that established behavior can be distinguished from working hypotheses and unresolved protocol fields.

High-Level Model

The diagnostic protocol can be understood through four principal concepts:

Device
  ↓
Module
  ↓
Object
  ↓
Configuration

Device

A Device is a physical component connected to the MyHOME/SCS system.

Examples include:

  • DIN-rail actuators;
  • flush-mounted actuators;
  • command devices;
  • shutter actuators;
  • dimmers;
  • sensors;
  • interfaces.

Each physical Device has a hardware identifier that can be used by the diagnostic protocol independently of its normal system address.

A diagnostic session generally begins by either discovering Devices or selecting an already-known Device.

See Diagnostic Device Discovery and Diagnostic Device Interview.

Module

A Device can expose one or more Modules.

Module is the terminology used by MyHOME Suite for the logical units presented within a physical Device. A Module does not necessarily correspond to a separate physical component, relay, button, or electronic channel.

For example, a single physical Device could expose:

Device
  │
  ├── Module 1
  ├── Module 2
  ├── Module 3
  └── Module 4

Internally, the diagnostic protocol identifies these Modules using a slot/index value. This internal slot index must not be assumed to be identical to the Module numbering displayed by MyHOME Suite.

See Device Modules and DIM30.

Object

Each Module is associated with an Object defining the logical function implemented by that Module.

Examples include:

Light actuator
Dimmer actuator
Shutter actuator
Light control
Automation control
Scenario control
Presence sensor

Objects correspond to what the MyHOME Suite catalogue database calls Key Objects, historically abbreviated as KO during the reverse-engineering work.

For documentation purposes, the preferred terminology is:

Object ID 6    → Light actuator
Object ID 8    → Dimmer actuator
Object ID 218  → Shutter actuator
Object ID 400  → Light control

rather than KO6, KO8, KO218, and KO400.

Some configurable Modules can initially contain a Virgin Object, representing the set or class of Objects that may subsequently be assigned to that Module.

The diagnostic protocol uses DIM30 to describe the relationship between Modules and Objects.

See Objects, Virgin Objects, Device Modules and DIM30, and Diagnostic DIM Reference.

Configuration

An Object can have a set of configuration properties defining its behavior.

Depending on the Object, these can include information such as:

  • addresses;
  • operating modes;
  • timing parameters;
  • button assignments;
  • scenario numbers;
  • sensitivity levels;
  • shutter presets;
  • groups.

The available properties depend on the Object, Device, and firmware.

Within the diagnostic protocol, much of this configuration is exchanged using DIM35.

Conceptually:

Device
  │
  └── Module
        │
        └── Object
              │
              ├── Property
              ├── Property
              ├── Property
              └── ...

The MyHOME Suite catalogue database provides the metadata necessary to translate many of these raw protocol values into meaningful configuration properties.

See Module Configuration and DIM35 and MHCatalogue Configuration Schema.

Diagnostic Domains

Diagnostic communication is divided into multiple Diagnostic WHO domains.

A Diagnostic WHO appears to define a device discovery and configuration environment rather than simply being the diagnostic equivalent of one ordinary runtime WHO.

For example, the Automation configuration domain includes devices whose Objects can subsequently participate in different runtime functions:

                 Diagnostic WHO 1001
                         │
                         ▼
                 Automation Device
                         │
             ┌───────────┴───────────┐
             ▼                       ▼
         Module 1                 Module 2
             │                       │
             ▼                       ▼
      Light actuator          Automation control
             │                       │
             ▼                       ▼
     runtime Lighting        runtime Automation

This explains why the relationship between Diagnostic WHO and ordinary runtime WHO should not necessarily be expected to be one-to-one.

The addressing topology also differs between functional domains. Automation uses A/PL addressing, while Temperature Control, Energy Management, and Access Control have their own domain-specific addressing concepts.

See Diagnostic WHO Domains.

Diagnostic Workflow

Although individual Diagnostic WHO domains can use different addressing schemes, the current evidence suggests a common high-level workflow.

DISCOVER
   │
   ▼
Physical Device
   │
   ▼
SELECT
   │
   ▼
INTERVIEW
   │
   ├── identity
   ├── firmware
   ├── diagnostics
   └── hardware ID
   │
   ▼
ENUMERATE MODULES
   │
   ▼
Identify Objects
   │
   ▼
READ / WRITE CONFIGURATION
   │
   ▼
FINALIZE

Discovery

Devices can be discovered using their hardware IDs or through the native addressing topology of the Diagnostic WHO domain.

When the Device is already known, discovery can be skipped and the Device can be selected directly.

See Diagnostic Device Discovery.

Interview

Once selected, the Device reports information describing its identity, firmware, diagnostic state, hardware ID, Modules, and other device-level information.

See Diagnostic Device Interview and Diagnostic DIM Reference.

Module and Object Enumeration

The Device reports the Modules exposed by its firmware and the Object associated with each Module.

For the Automation diagnostic domain, this is primarily performed using DIM30.

See Device Modules and DIM30.

Configuration Reading

After the Device structure is known, MyHOME Suite can retrieve the configuration associated with its Modules and Objects.

For many Objects this information is transported using DIM35.

See Diagnostic Configuration Reading.

Programming

The same model can be used in the opposite direction to configure a Device.

MyHOME Suite configuration
          ↓
        Object
          ↓
        Module
          ↓
Diagnostic write messages
          ↓
        Device

Programming can assign an Object to a configurable Module and write the properties associated with that Object.

See Diagnostic Device Programming.

Diagnostic Protocol Layers

The overall relationship between diagnostic configuration and normal OpenWebNet operation can therefore be represented as:

              Diagnostic WHO
                    │
                    ▼
       Discovery / Configuration Domain
                    │
                    ▼
              Physical Device
                    │
                    ▼
                 Modules
                    │
                    ▼
                 Objects
                    │
                    ▼
              Configuration
                    │
                    ▼
          Runtime functionality
                    │
                    ▼
          Ordinary OpenWebNet WHO

The Diagnostic WHO establishes the environment in which physical Devices are discovered and configured.

A Device represents physical hardware on the bus.

A Module represents a logical unit exposed by that Device.

An Object defines the function assigned to the Module.

The Configuration defines how that Object behaves.

Once configured, those Objects participate in the appropriate ordinary OpenWebNet runtime protocols.

Further Reading

The detailed protocol is divided into separate wiki topics:

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