Protocol Converter Node (PCN)

| Overview

The PCN (Protocol Converter Node), or SmartNode V2 device, is a core edge component that enables local control, sequencing, and data aggregation within the building management and IoT ecosystem. 

It acts as an intelligent intermediary between field devices and the central control infrastructure, supporting Modbus-based communication, local logic execution, and scalable device integration.

PCN is engineered to operate both as a standalone controller and as part of a distributed control architecture, where it aggregates data from connect modules, executes low-code control sequences, and reliably forwards processed information to higher-level systems such as CC and CCU. The device emphasises flexibility, modular expansion, and future-ready protocol support.

In its current phase, the PCN focuses on core PCN functionality, enabling local sequencing and Modbus RS-485 connectivity through Smart Node V2. 

While advanced integrations such as BACnet, external AQ devices, and full connect module orchestration are part of the roadmap, the existing implementation already delivers a robust foundation for edge-level automation and control.

Key characteristics of the PCN include:

• Local execution of low-code control sequences
• Acting as a data aggregator and mediator between field devices and central systems
• Support for RS-485 Modbus communication
• Scalable model and sequence configuration
• Clear device identification using Slave ID and Server ID

| System Architecture

Core Components

The complete feature consists of three major parts:

1. SmartNode V2 Device
   • Runs a low‑code sequence locally
2. Modus Equipment (EM )
3. Connect Module

Current Implementation Status

• PCN core functionality is completed
• External AQ integration – Not completed
• Connect Module integration – Not completed

Currently, only the SmartNode V2 device running local sequences is operational.

| How it Works

The PCN architecture is designed around the SmartNode V2 acting as both a central controller and an intelligent aggregator. All Connect Modules, as well as any other external Modbus-compatible equipment, interface with the SmartNode over RF communication, enabling both control and data exchange through a unified node.

While the Connect Module itself is intentionally built with limited processing capability, the introduction of SmartNode V2 significantly elevates the overall system intelligence. SmartNode V2 joins the ecosystem as a high-capability control layer, capable of hosting and executing advanced control sequences. These sequences can be created in the portal and seamlessly pushed to the device, allowing complex logic to be deployed without on-site reconfiguration.

By centralising control, sequencing, and aggregation within the SmartNode, the PCN architecture achieves a clear separation of roles:

• Field devices and Connect Modules focus on sensing and actuation

• SmartNode V2 handles coordination, decision-making, and system-level control logic

This architectural approach provides exceptional flexibility and scalability. New devices, control strategies, or external systems can be integrated with minimal disruption, while still maintaining robust and deterministic control behaviour.

Collectively, these capabilities make the PCN a one-of-a-kind control mode within the 75F ecosystem. It combines distributed device connectivity with centralised intelligence, enabling highly adaptable control strategies suited for a wide range of building types and operating conditions. As a result, PCN delivers a powerful, future-ready setup that meets both current and evolving building automation needs.

| Wiring

Below are the possible connections achievable using the PCN

CCU - SmartNode V2 Via RF

In this setup, the CCU communicates wirelessly (RF) directly with a SmartNode V2.
The SmartNode V2 acts as the field controller, handling thermistor/analog inputs, analog outputs, and relay outputs locally.

CCU - SmartNode V2 Via RF SmartNode, SmartNode- Connect Module Wired

Here, the CCU connects via RF to a SmartNode V2, which then communicates over a wired connection to a Connect Module.
The Connect Module expands I/O capacity, allowing additional inputs, analog outputs, and relay outputs to be controlled under the SmartNode.

CCU - SmartNode V2 Via RF SmartNode, SmartNode- Connect Module Wired, SmartNode - Modbus EM Wired

In this configuration, the CCU communicates via RF with the primary SmartNode V2, which is wired to a Connect Module for extended I/O and also wired to a Modbus Energy Meter (EM).
The SmartNode aggregates I/O control and Modbus energy data, forwarding both to the CCU.

CCU - SmartNode V2 Via RF SmartNode, SmartNode - Modbus EM Wired

Here, the CCU connects via RF to a SmartNode V2, which is directly wired to a Modbus Energy Meter.
The SmartNode reads Modbus inputs (energy data) and communicates the information wirelessly to the CCU, without additional Connect Modules.

| Configuring a PCN Zone

To configure a PCN zone.

From the CCU floor layout screen.

• Add a zone.
• Click Pair Module.

• Select the Custom Equipment from the select device type screen.

• Select the Protocol Converter Node from the module type selection screen.

• Follow the pairing instructions in the device and pair the device. You can manually pair the device as well. For manual pairing of PCN, refer to Alternate or Manual Pairing of PCN.

• Click Pair to start the pairing process.

Once paired successfully, the PCN configuration screen displays as shown below.

• Create the required sequence from the sequencer for the SmartNode V2.

• Push the Sequence to the SmartNode.

The Sequence is pushed to the SmartNode V2, and the model is made available for configuration as shown below.

For more information on seqeunce creation and pushing to device refer to Connect Module as Zone

• Configure the registers required to be displayed on the UI, and the schedulable registers.
• Click Add Connect Module to add a Connect module to the configuration.

• Create the required sequence from the sequencer for the connect module.

• Push the Sequence to the SmartNode.

• The Sequence is pushed to the Connect Module, and the model is made available for configuration as shown below.

• Configure the registers required to be displayed on the UI, and the schedulable registers.
• Click the cross icon to delete the connect module.

• Click Add External Euip to add an external Modbus equipment.

The external equipment selection window displays.

Note: The maximum permitted number of registers is 50 for an integer type register, and 25 is the maximum for a float type register.

• Select the required model from the available list.

The model is added into the configuration as shown below.

• Click the cross icon to delete the connect module.

• Configure the registers required to be displayed on the UI, and the schedulable registers.

• Click Add External Equip to add more euipment.

Note: The 18 registers are preoccupied by the previously added equipment, and the remaining out of 50 is available for use.

• Add the second based on the remaining register left.

The selected equipment is added to the configuration as shown below.

• Configure the registers required to be displayed on the UI, and the schedulable registers.

• Click Save to confirm the configuration.

The PCN profile is configured as below.

| Configuration Parameters

The BaudRate will have to be set according to the external Modbus device connected to the SnartNode via RF.

Parity, DataBits, and StopBits need to be configured accordingly.

| Communication & Control Flow

Modbus RS-485 Connectivity

Smart Node V2 supports RS-485 Modbus.

Data & Control Flow

CCU sends register configuration and control definitions. CCU does not originate controls.

SmartNode V2 executes  Local sequencing & Data aggregation

| Protocol Support

Supported Protocols

• Modbus (RS-485) – Supported
• BACnet – Not supported currently

Key Notes

• BACnet is not available in the PCN at this stage.
• All testing and validation must be done only using Modbus connectivity.

| Register Configuration & Data Types

Register Limits

The system currently supports 25 registers when parameters are configured as Float. A Float data type consumes 2 Modbus registers, which is why the limit is reduced to 25.

If parameters are configured as Integer, the system can support up to 50 registers, since an Integer uses only 1 register.

Current Behavior

All parameters are set to Float by default. This behaviour is similar to the current existing model, where Float is the default data type.

Planned Enhancement

A new column will be introduced in the Header (Head‑Off) configuration to define the parameter data type:

• Integer
• Float

Based on the selected data type:

• Integer parameters will increment the register count by 1
• Float parameters will increment the register count by 2
• The Portal will handle this configuration and send the correct Register ID mapping to the CC.
• The CC will then forward the mapping to the Field Device / Controller.

Note: Until this enhancement is implemented, all parameters should be treated as Float-only.

| PCN Functional Role

PCN as Aggregator

SmartNode V2 aggregates data from Local sequences & Connect modules & pushes processed data to CCM.

Control Execution

SmartNode V2 can execute relay operations, write values to Modbus points

Written values are reflected in the same point. Communicated upward to CCU.

| Device Identification & Server IDs

Slave ID & Server ID

Each device communicates using a unique Slave ID. Devices also have a unique Server ID, which is the primary differentiator.

Identification Logic

Data is polled based on register addresses, not just Server ID. Server ID ensures Correct data mapping & Proper identification of the data source

Example Scenario

If the system contains: 1 SmartNode V2 & 3 Connect Modules

Then the total devices = 4 

Each Connect Module has a unique Slave ID & a unique Server ID

This guarantees correct data routing from each module to the CCU.

| Sequencing & Model Configuration

Sequence Deployment

• Sequences can be applied to:
  • SmartNode V2 device
  • Connect Module (if AQ is removed)

Model Configuration Limits

• Connect Module:
  • Supports up to 8 models (equips)
• SmartNode V2 + Connect Modules Combined:
  • Up to 3 Connect Modules + 1 SmartNode V2
  • Each Connect Module supports 8 models
  • Total configuration capacity: 24 equips

Model Structure

Each Connect Module acts as a sub‑cube. Under each sub‑cube, multiple sequences can exist, such as:

• Exhaust Fan Sequence
• AC Sequence
• Lighting Sequence
• Other functional sub‑sequences

Sequence creation defines how models are grouped and executed.

| Summary

At present, the system supports Modbus‑based PCN core functionality with Float‑only registers and limited sequencing. The architecture is designed to scale with upcoming Phase‑2 enhancements, enabling flexible data types, full connect module support, and richer multi‑device orchestration.

| OTA Capability for PCN

An OTA upgrade capability is also made available for the SmartNode V2 & Connect Module.

The OTA can also be triggered from the CCUs and Zones widget screens, as shown below.