Optimizing Industry 4.0 Communication Architectures using Multi-Protocol I/O Hubs and Converters

Communication protocols are important in supporting real-time data transfers and control in Industry 4.0 and Industrial Internet of Things (IIoT) networks. Sensors, actuators, motor drives, and controllers all have specific communication needs. There’s no “one size fits all” communication protocol.

While no single protocol suits every application’s requirement, diverse devices often need to be linked. Sensors must be linked to controllers, and controllers must connect with various system elements that use different protocols like IO-Link, Modbus, and multiple forms of Ethernet.

In many instances, the entire machine needs to connect with the Cloud. That results in complex communication architectures with a myriad of protocols. To address that challenge, machine designers can turn to multi-protocol input/output (I/O) masters, hubs, and converters.

This article begins with a review of common Industry 4.0 communication protocols and where they fit into the networking hierarchy. It then presents a series of I/O masters, hubs, and converters from Banner Engineering, reviews their operation, and discusses how they can facilitate complex Industry 4.0 and IIoT communication architectures.

What is the OSI seven-layer model?

Network communication protocols are often described in the context of the Open Systems Interconnection (OSI) seven-layer model. The model starts with three media layers that deal with hardware considerations, such as physical, data link, and network connections.

Data addressing is the focus of the next three layers, which include the transport, session, and presentation processes.

The seventh level of the model is the application layer, which provides the interface between the user and the network. Protocols like Modbus and PROFINET reside in this layer. The OSI model is more loosely related to other protocols like EtherNet/IP.

In the case of EtherNet/IP, the application layer includes processes like web access (HTTP), e-mail (SMTP), file transfers (FTP), etc. The three Host layers implement the Transmission Control Protocol/Internet Protocol (TCP/IP) processes for establishing sessions, making error corrections, etc. The Media layers include the physical 10 Base-T connection and the implementation of the Ethernet data link and network connections (Figure 1).

Figure 1: How EtherNet/IP relates to the OSI seven-layer model. (Image source: Banner Engineering)

Where does IO-Link fit in?

IO-Link is a single-drop digital communication interface (SDCI) for small sensors, actuators, and similar devices. It extends bidirectional communications down to individual devices on the factory floor. It’s specified in IEC 61131-9 and is designed to be compatible with industrial network architectures based on Modbus, PROFIBUS, EtherNet/IP, etc.

IO-Link uses a Master device to connect IO-Link devices to higher-level protocols like Modbus that provide connections to data-consuming devices like programmable logic controllers (PLCs), human-machine interfaces (HMIs), a cloud data service (CDS), and so on. At the lowest level, IO-Link uses Hubs to aggregate multiple devices and feed the data up to a Master device. In addition, an analog voltage to the IO-Link Converter can be used to add analog sensors to the IO-Link network (Figure 2).

Figure 2: IO-Link converters, hubs, and masters can collect data from field devices and push it up to data consumers like PLCs, HMIs, and CDS. (Image source: Banner Engineering)

Why combine IO-Link with other protocols?

Mass customization and flexible production processes are distinguishing characteristics of Industry 4.0. Combining IO-Link with other protocols can increase the flexibility and versatility of Industry 4.0 factories. Beneficial characteristics of IO-Link include:

• Modbus has limited support for analog devices like certain sensors, while IO-Link is compatible with both digital and analog devices.
• Increased factory automation and expansion can be facilitated using a gateway that supports both IO-Link and higher-level protocols like Modbus TCP or EtherNet/IP and can function as a bridge between a field-level sensor network and an industrial network communications backbone.
• IO-Link increases operational efficiency by providing a standardized, uniform configuration process for all sensors, and it can be used to replace defective sensors automatically when an identical model is used.
• The data collection and communication capabilities of IO-Link provide increased visibility into the operation of individual sensors, as well as dispersed sensor networks, and speed the data up to a PLC and the Cloud.

How do you combine Modbus and IO-Link?

One of the first tools to consider is a hybrid I/O Modbus hub like the 8-port bimodal to Modbus R95C-8B21-MQ. This discrete bimodal to Modbus hub connects two discrete channels to each of the eight unique ports, providing access to monitor and configure those ports via Modbus registers.

Hybrid I/O Modbus hubs are available with four configurable analog inputs (voltage or current) and four analog outputs, plus eight configurable PNP (sourcing) or NPN (sinking) discrete inputs and outputs for increased application flexibility.

DXMR90-X1 industrial controllers can be used as a platform for IIoT solutions. They can consolidate data from multiple sources for local data processing and accessibility. The DXMR90 contains individual Modbus clients supporting simultaneous communication to up to five independent serial networks.

The DXMR90-X1 includes one female M12 D-Code Ethernet connector and four female M12 connections for Modbus master connections. Other DXMR90 models are available with two female M12 D-Code Ethernet connectors and four female M12 connections for Modbus client connections or with one female M12 D-Code Ethernet connector and four female M12 connectors for IO-Link master connections.

All DXMR90 controllers also include one male M12 (Port 0) for incoming power and Modbus RS-485 and one female M12 for daisy chaining Port 0 signals. Additional features of the DXMR90-X1 include (Figure 3):

• Converts Modbus RTU to Modbus TCP/IP, EtherNet/IP, or Profinet
• Internal logic driven by action rules for easy programming, or MicroPython and ScriptBasic for developing more complex solutions
• Support for Internet protocols, including RESTful and MQTT
• Well-suited for IIoT data analytics, condition monitoring, predictive maintenance, overall equipment effective (OEE) analysis, diagnostics, and troubleshooting

Figure 3: The DXMR90-X1 controller can be used in conjunction with the R95C hybrid I/O Modbus hub. (Image source: Banner Engineering)

What is multi-protocol support?

The DXMR110-8K 8-port IO-Link master is a compact, multi-protocol smart controller that consolidates, processes, and distributes IO-link and discrete data from multiple sources. Connections include:

• Two female M12 D-Code Ethernet connectors for daisy chaining and communication to a higher-level control system
• Eight female M12 connections for IO-Link devices
• One male M12 for incoming power and one female M12 for daisy chaining power

The DXMR110 supports cloud connectivity and includes advanced programming features. ScriptBasic and action rules programming can be used to create and implement custom scripts and logic for optimized automation processes.

The internal processing power of the DXMR110 can be used to move data processing to the edge, minimizing the need for hardware in the control cabinet and eliminating I/O cards on a PLC. Integrated cloud connectivity can make data accessible from anywhere in the world. Finally, the IP67 housing simplifies installation in any location by eliminating the need for a control cabinet (Figure 4).

Figure 4: The DXMR110-8K 8-port IO-Link master is a multiprotocol smart controller. (Image source: Banner Engineering)

There’s more

The devices presented so far are not the only options for implementing multi-protocol industrial communication solutions. Machine designers can employ a range of Banner Engineering's remote I/O blocks to optimize system design, space efficiency, and performance.

Banner offers in-line converters and masters with over-molded designs that meet the ingress performance (IP) demands of IP65, IP67, and IP68. The R45C series in-line converters and masters provide a gateway for connecting IO-Link devices to an IIoT network or system controllers using the Modbus RTU protocol. Model R45C-2K-MQ connects two IO-Link devices to a Modbus RTU interface.

When analog signals are required, designers can turn to the R45C-MII-IIQ Modbus for a dual analog in-line I/O converter. Functions include:

• Analog in. When the converter receives an analog input, it sends the numerical representation of the value to the corresponding Modbus register. It can accept analog inputs from 0 to 11,000 mV or 0 to 24,000 µA.
• Analog out. The converter outputs an analog value corresponding to a numerical input. Analog outputs can range from 0 to 11,000 mV or 0 to 24,000 µA.
• Process data values outside the valid range (POVR) can also be detected and processed, and the converter sends a signal to the system.

When a single analog input needs to be converted to an IO-Link signal, designers can use the S15C-I-KQ. This cylindrical analog current to IO-Link converter connects to a 4 to 20 mA current source and outputs the corresponding value to an IO-Link master.

Banner offers a variety of Modbus RTU I/O blocks that support connections of multiple analog and discrete devices connected to a Modbus or IO-Link network. They can be mixed or matched to support flexible system designs and interoperability (Figure 5).

Figure 5: Examples of the form factors and configurations of Banner’s remote I/O solutions for IO-Link integration. (Image source: DigiKey)

Can wireless protocols be integrated?

Banner’s Sure Cross DSX80 Performance wireless I/O network solution enables wireless connectivity. It can be used independently or connected to a host PLC using Modbus or a personal or tablet computer. The basic system architecture comprises a Gateway and one or more Nodes (Figure 6).

Figure 6: Banner’s Sure Cross DSX80 Performance wireless I/O network solution includes a gateway and one or more sensor nodes. (Image source: Banner Engineering)

Implementing a Sure Cross DX80 Performance wireless network involves three elements: the network topology, master and slave relationships, and the time division multiple access (TDMA) architecture.

A star topology is used where the master maintains a separate connection with each node. If the connection between a node and the master fails, connectivity with the rest of the nodes is unaffected.

A gateway like the DX80G2M6-QC is the master device and initiates all communication with the slave devices. A gateway that uses a Modbus RTU RS-485 connection acts as a slave to a Modbus RTU host controller. A single wireless network can include up to 47 slave nodes.

Slave devices can be wireless nodes like the DX80N9Q45DT dual thermistor temperature sensor node, the DX80N9Q45PS150G pressure sensor node, or vibration and humidity sensors.

Slave devices can’t initiate communication with the gateway or communicate with each other. A serial data radio like the DX80SR9M-H can be added to extend network coverage to accommodate physically large installations.

TDMA is the key to combining robust connectivity with minimal energy consumption. The TDMA controller in the gateway assigns each node a specific time to send and receive data. The gateway always has device ID number 0. Nodes may be numbered in any order using device IDs 1 through 47.

Setting specific communication times for individual nodes optimizes efficiency by eliminating the possibility of conflicts between nodes. It also enables nodes to enter a low-power state between communications, only waking up at the assigned time. Turning off the radio between transmissions conserves power and extends the operating life of battery-powered nodes.

Conclusion

Access to multiple communication protocols, like IO-Link, Modbus, EtherNet/IP, and so on, is necessary to support the efficient operation of Industry 4.0 and IIoT networks. Banner Engineering provides designers with a comprehensive selection of IO-Link hubs, converters, and masters in various form factors to support optimized communication solutions.