Special
Great potential for SPE and APL
Single Pair Ethernet (SPE) and Advanced Physical Layer (APL) bring Ethernet to the field level. Data and power are transmitted over a single pair of wires—over long distances, robustly, and IP-based from the sensor to the cloud.
In the field of information technology, Ethernet and IP-based protocols have long since become the standard communication solution. Industrial Ethernet is the common collective term for standards used to establish this technology in the manufacturing and process industries, as well as many other sectors.
Single Pair Ethernet (SPE) and Advanced Physical Layer (APL) are terms that have recently emerged in the field of Industrial Ethernet. This technology also has great potential in many other applications and is therefore of particular interest to embedded systems developers.
What is Single Pair Ethernet? (SPE)
Single Pair Ethernet (SPE) was originally developed for automotive applications under the name BroadR-Reach. Communication takes place via a single twisted pair of wires. Conventional Ethernet networks use 2 or 4 pairs, i.e. up to 8 wires.
The main drivers behind the development of SPE were to reduce space requirements and weight, thereby saving effort and costs. This is particularly advantageous in vehicles, robotics, and sensor technology.
In the ISO/OSI reference model, Single Pair Ethernet only describes the physical layer (layer 1). It is a method of transmitting data bidirectionally over a pair of wires. All layers above this correspond to the familiar and widely used network methods. SPE thus enables end-to-end IP-based communication from the sensor or actuator to the cloud with a uniform protocol standard for the Industrial Internet of Things (IIoT).
There are now SPE standards with data rates ranging from 10 Mbit/s to 1 Gbit/s and, depending on the standard, ranges of up to 1000 m. Optionally, the same wire pair can be used to supply power to end devices (Power over Data Line = PoDL). SPE is now used in many industrial and automotive applications. It is characterized by high EMC robustness and supports real-time capability using time-sensitive networking technology (TSN).
In the automotive sector, cameras, radar, lidar, sensor and actuator networks, i.e., the entire vehicle network communication, can be uniformly wired using SPE and communicate with control units.
In industrial automation, SPE is used for the uniform wiring of sensors and actuators, IO modules, field devices, and controllers. In mechanical engineering and robotics, SPE demonstrates its strengths due to the reduced number of wires in drag chains, dynamically moving applications, and space-critical designs.
Was ist Advanced Physical Layer (APL)?
Due to the long distances that can be bridged using SPE standards and the high availability, SPE is also an attractive technology for the process industry. Advanced Physical Layer (APL), an SPE standard for transmission rates of 10 Mbit/s over distances of up to 1000 m, was developed specifically for this industry and can also be used intrinsically safely in potentially explosive areas (Ex areas).
In addition, existing fieldbus cables or 4-20mA wiring can be reused. To simplify matters, the polarity of the two wires does not need to be taken into account.
Summary
Embedded developers should familiarize themselves with SPE and APL. Ethernet and IP-based protocols are thus penetrating down to the lowest field level and replacing classic fieldbuses. Only one pair of wires is required for the network, and data and energy can be transmitted over long distances. This simplifies the implementation of networks and device interfaces, reduces costs, and enables new device concepts.
APL also opens up access to the process industry and hazardous areas, which are long-lasting and stable markets. The use of a transparent network from the sensor to the cloud reduces costs, provides greater flexibility, and opens up new possibilities for many areas of application.