Third party system integration

In building technologies, integration of 3rd party systems, such as chillers, lighting, lifts etc. into the building control system is considered as standard.

Domat provides a broad range of software drivers which help to complete this task.

When specifying and designing integrated systems, it is necessary to get in touch with the 3rdparty supplier so that it is possible to specify which functions are available and at what costs.

The first thing is: Will the 3rdparty system be integrated into a process station, or into a management station?

Integration into process stations

There must be a communication interface free in the process station. Typically, it is a serial port. In some cases, a RS232/RS485 converter (e.g. R012) must be used. If a PC-based process station (e.g. IPCT.1) has no free serial port available, it may be created using a terminal server (R020R031), which creates a virtual serial port available over the Ethernet network. If there are standard protocols used, a Modbus RTU/TCP router, or R025 (RS232), R035 (RS485) is a good solution.

The process station must provide the necessary communication protocol (driver). In SoftPLC, there are more than 60 protocols available at the IPLC5.. and Windows runtime. The Merbon PLCs now contain drivers for Modbus RTU, Modbus TCP, M-Bus and IEC 62056-21. However, there are third party devices which use a specific protocol. Merbon IDE allows writing of customized drivers in the ST language, which brings more flexibility and independence for the engineers.

The drivers in Merbon IDE can be divided into following groups:

  • Native drivers supported in Merbon IDE: They are part of the IDE and are configured by adding a communication channel and defining the required driver from the list. Driver properties, such as baudrate and addresses, are set in the property grid. Native drivers are fully supported by Domat, and their updates are part of the new Merbon IDE releases. The drivers source codes are part of Merbon IDE source codes and are not available to the public.
  • ST drivers written by Domat on demand: if a customer needs to develop a new driver, there is the protocol description available, and the development is technically feasible, Domat can write the driver in ST language as a paid service. The customer gets a complete, fully commented source code which is fully at his disposal. The invoiced sum does not fully cover the development costs, and therefore the source code is a property of Domat Control System. Domat may decide to make the driver available to the public, including its source codes (or part of it), at the web forum, so that also other Merbon IDE users may take advantage of it. Domat is not responsible for keeping the driver updated nor for a full functionality of the published code, as third-party systems may be subject to updates, and Domat is not able to follow these changes and keep the drivers up to date continuously.
  • ST drivers written by customer: The code is sole property of the customer, who decides if the code will be available to public or not; if it will be published for free or on a paid basis, and if so, if  on his web pages, on the Domat forum, or anywhere else; if any support will be provided for the code, and if so, if the support shall be paid or free of charge, etc. The same rules as for an ordinary application program apply.

Integration into SCADA

As Merbon SCADA provides a SoftPLC Runtime driver, third party integration directly into SCADA follows over the SoftPLC Runtime running on the same PC as Merbon SCADA or on another PC in the network. The integration layer is separated from the SCADA and can be configured autonomously. The SoftPLC Runtime must be licensed separately (in the price list as RC-SoftPLC).


Topology for third-party integration into Merbon SCADA

The PC must have all necessary communication ports. If the integration follows over the Ethernet, no other hardware is necessary. If serial ports (RS232, RS485) are required, a more suitable solution is using IPLC510(which contains 2×RS232 ports and 2×RS485 ports) rather than the SoftPLC Runtime..

Available protocols

All drivers are contained in the corresponding license (SoftPLC or Merbon).

The current list of supported protocols can be found at

Rules for successfull integration

When integrating a 3rd party device, the required data volume and character must be considered.

For several analogue / binary data points it is mostly good enough to use hardware connection with I/O modules.

At applications with dozens or hundreds datapoints and special signal types, such as discrete and cumulative values (error numbers, energy metering), it is better to use data integration. However, the 3rdparty data protocol must be available, together with a list of values and their addresses and meaning. If planning to use already implemented drivers, check the version or variant of the protocol, such as Modbus ASCII / RTU, master / slave role, etc).

Before final design, a consultation with a Domat Control System representative is advisable. A properly designed project and clear tasks for all parties prevent unwanted extra costs and time delays during commissioning.