RFID readers, as the most important information collection devices in the industrial sensing layer, serve as a bridge between the physical and digital worlds. So how do they connect to the Industrial Internet of Things (IIoT)? Faced with a variety of heterogeneous devices and systems in the industrial field, IIoT access becomes very complex. To understand how to connect to the IIoT, we must first understand the communication protocols used in the IIoT.
Due to the strong closed nature and complexity of industrial hardware and software systems, the industrial field has a multitude of communication protocols, including PROFIBUS, Modbus, CAN, HART, EtherCAT, EthernetIP, Modbus/TCP, PROFINET, OPC UA, and numerous vendor-specific protocols. In industrial settings, equipment from different manufacturers uses different industrial protocols. To achieve interconnection of all devices, it is necessary to parse and convert data from various protocols, which is time-consuming and labor-intensive. To ensure real-time and rapid acquisition of industrial information, current industrial data acquisition primarily uses wired device access methods, mainly including fieldbus, industrial Ethernet, and Ethernet. Industrial Ethernet generally refers to technology that is technically compatible with standard Ethernet while taking improvements to make it more suitable for industrial application scenarios.
Fieldbus
Fieldbus technology is an industrial communication technology developed internationally in the late 1980s and early 1990s. It's a serial, digital, multi-point, bidirectional data bus used for communication between field devices and instruments installed in production process areas and automatic control devices or systems in control rooms. For the past two decades, fieldbus has been the mainstream solution for field-level data communication systems.
Due to its simplicity, reliability, cost-effectiveness, and other outstanding advantages, fieldbus is widely used in the industrial field. It operates at the bottom layer of automation systems, primarily addressing two issues: communication between intelligent instruments, controllers, and actuators in the industrial field, and information transmission between field control devices and upper-level control systems. For example, industrial data readers use fieldbus to transmit collected information to higher-level systems.
Fieldbus uses measurement and control devices as network nodes and twisted-pair coaxial cables as transmission media to connect measurement and control devices with digital computing and communication capabilities located in the production field into a network. Following publicly available communication protocols, it enables data transmission and information exchange between multiple measurement and control devices, as well as between measurement and control devices and remote monitoring computers. Industrial Ethernet
Ethernet is the most widely used computer network technology. The widespread application of 802.3 and TCP/IP network technologies in the industrial field represents a crucial direction for the future development of the Industrial Internet of Things (IIoT). Following the OSI network model, 802.3 and TCP/IP technologies offer easy interconnectivity between devices from different manufacturers. Ethernet technology is mature, offering a wider selection of software and hardware vendors, and its low cost is another advantage.
Industrial Ethernet can build interconnected, interoperable, and transparent integrated industrial control networks, achieving seamless connection between industrial control networks and enterprise information networks. This forms a fully open, enterprise-level integrated management and control network, enabling seamless industrial communication from the management and control layers to the field device layers.
With the continuous advancement of Ethernet technology, standard Ethernet is increasingly being directly applied to many IIoT scenarios, such as smart buildings, urban management, logistics, and public transportation. These scenarios do not have high requirements for data timeliness and allow for short-term network interruptions. For ubiquitous device connectivity, standard Ethernet and the TCP/IP protocol stack are undoubtedly very convenient.
What protocols are used in both access methods?
Fieldbus uses a digital bus topology, significantly simplifying wiring. Several devices are distributed along this bus, and the system issues various production commands to each device, much like the human brain controls bodily actions through the nervous system. Because field devices possess varying degrees of digital computing capabilities, they can be distributed throughout the factory, forming a distributed system. Currently, there are as many as 40 fieldbus protocols on the market, with commonly used ones including Modbus, PROFIBUS, DeviceNet, Foundation Fieldbus, LonWorks, and CAN. Modbus is a serial communication protocol commonly used between industrial electronic devices. It is currently one of the industry standards for industrial communication protocols and is widely used for general communication tasks at the factory level.
Common industrial Ethernet protocols include Modbus/TCP, Ethernet/IP, PROFINET, and EtherCAT. Based on their compatibility with standard Ethernet, industrial Ethernet can be divided into three categories. The first type is fully compatible with standard Ethernet, such as Modbus/TCP, Ethernet/IP, and PROFINET NRT. Both real-time and non-real-time data are transmitted via IP. Its advantages are low cost, ease of implementation, and full compatibility with standard Ethernet. The second type uses a standard Ethernet controller. Real-time data is not transmitted via TCP/IP but uses a dedicated real-time protocol. The TCP/IP protocol stack still exists for transmitting non-real-time data. PROFINET RT belongs to this category. The third type uses a dedicated Ethernet controller with a dedicated real-time protocol, requiring dedicated protocol chips and dedicated switches. It offers strong real-time performance but is expensive. EtherCAT slaves (EtherCAT masters can use standard Ethernet) and PROFINET IRT belong to this category.
How can
RFID readers connect to the Industrial Internet of Things (IIoT)?
The following diagram, using AnDe Electronics'
RFID reader as an example, illustrates how
RFID devices can connect to the IIoT in two different ways: via bus and industrial Ethernet. Currently, fieldbus is the primary communication method at the control layer and field device layer of industrial automation control networks. With the deepening and expansion of industrial automation control, unified communication standards have become the recognized development direction, and industrial Ethernet technology will become an important alternative to fieldbus technology.
