Roland Gémesi, Senior Systems Engineer & Kiruba Subramani, Senior Systems Engineer, Silicon Labs, Ofer Blonskey, Chief Technology Officer, CoreTigo
A key enabler on Industry 4.0 is effective machine connectivity, including in places that were not possible before, for more intelligent devices at the edge.
For industrial applications, the traditional solution is wired communication, which provides high reliability and low latency. However, cables limit the flexibility and agility of machines, they are expensive to maintain, they can degrade and break, and they cannot be used with motion control solutions that move or rotate rapidly.
Conventional wireless communication is unsuitable, as it cannot meet the strict industrial requirements for reliability, latency, and scalability for control and monitoring.
This means that Industry 4.0 needs industrial-grade wireless, that can excel in harsh environments. In this article, we discuss one approach, IO-Link Wireless.
Wireless industrial communication
An extension to the existing IO-Link standard, IO-Link Wireless high reliability deterministic wireless communication standard for control and monitoring for factory automation.
Based on the IO-Link IEC 61139-9 standard, IO-Link Wireless offers industrial reliability, low latency, scalability, and deterministic communication. It meets the demands of Industry 4.0 and is widely implemented.
IO-Link Wireless enables seamless, vendor-agnostic communication. It expands on the advantages of wired IO-Link, offering a single wireless protocol for both control and monitoring. As well as connecting machines, IO-Link Wireless supports additional applications and systems, such as rotating components, wireless intelligent tooling, and transport track systems.
Deploying equipment based on the new standard is simple and cost-effective, for both retrofits and new builds. Without the limitations of cabling, wireless systems can provide more flexibility and modularity. There is no difference in how IO-Link Wireless data is processed, compared to the existing IO-Link standard, thus simplifying implementation.
Reliable and deterministic
IO-Link Wireless operates in the unlicensed 2.4 GHz Industrial, Scientific, and Medical (ISM) band. It communicates by using Gaussian Frequency Shift Keying (GFSK) RF modulation that, due to its constant envelope, provides inherent immunity for metal and multi path fading effects. It confines emissions to a narrow spectral band, making devices more immune to noise and interference.
It provides a reliability of 10-9 Cycle Error Rate, several magnitudes better than other wireless standards such as WLAN, Zigbee and Bluetooth, and which is like cable grade reliability.
An IO-Link Master, called W-Master, can have up to five radio transceivers, called tracks, each supporting up to 8 IO-Link W-Devices, thus adding up to 40 devices per W-Master (Figure 1). The W-Master tracks communications simultaneously on different frequencies, enabling optimal network utilization. For larger networks, multiple IO-Link Wireless Masters can coexist. IO-Link Wireless can also be added as a retrofitting option to existing wired IO-Link devices by using a W-Bridge or a W-Hub.
The protocol is designed to coexist with other wireless networks and interferers through adaptive frequency hopping. Channel exclusion is supported to avoid potential air collisions with other wireless systems, such as Wi-Fi. The W-Master controls the transmit timeframe of each W-Device, guaranteeing a fair share of air bandwidth.
A built-in automatic packet retransmission mechanism is used for critical data to ensure outstanding reliability while minimizing latency. This is implemented and controlled by the radio’s physical layer.
IO-Link Wireless was designed to provide deterministic communication. This is guaranteed by following a strict communication cycle, called W-Cycle, and by limiting the maximum number of wireless devices that can be serviced by a W-Master. IO-Link Wireless provides a deterministic latency of 5 ms while supporting up to 40 nodes (sensors, actuators, or I/O hubs) per W-Master.
IO-Link Wireless – System Architecture
When building an IO-Link Wireless capable device, manufacturers can select from different system architectures depending on their application constraints, such as cost and form factor. These are the three most common options:
● System on Chip (SoC): The most compact implementation, where even the higher layer of the IO-Link Wireless protocol features is executed on the SoC, resulting in a single chip solution.
● Wireless Co-Processor: More demanding applications can add a dedicated host processor and use the Wireless SoC as a co-processor. The two ICs are commonly interfaced via UART or SPI.
● System on Module (SoM): For shortest hardware development time, projects can be built around a fully integrated and certified IO-Link Wireless module implementation.
Figure 2 shows the block diagram of a suitable wireless SoC, providing computing power.
Click image to enlarge
Figure 2. Block Diagram of wireless SoC for IO-Link Wireless
hardware interfaces, analog and digital peripherals and a 2.4 GHz radio transceiver. It includes an Arm Cortex® M33 core running at up to 80 MHz, with 256 kB of RAM and 1536 kB of flash memory to support the implementation of the wireless stack, and optionally also the application code. The chip integrates a wide range of analog and digital peripherals, and hardware interfaces that make it suitable for multiple applications.
The SoC's bus system supports Direct Memory Access (DMA) and Peripheral Reflex System (PRS), thus enabling peripheral operation without continuous intervention by the MCU core. This significantly reduces execution latency and current consumption, thus improving battery life.
The integrated radio subsystem has a dedicated Arm M0+ core to perform low level transceiver operations. The integrated radio offers all the features required for an industrial-grade IO-Link Wireless device, such as adaptive gain control in the receive path, a 10 dBm RF power amplifier, receiver sensitivity of -97.6 dBm and in-depth configurability of the underlying radio PHY via a hardware abstraction layer and software API.
The radio features microseconds precision time synchronization, setting different radios and devices to the same time base, so that devices can act with very small jitter. It also provides fast RF mode and channel switching times, required by the IO-Link Wireless W-Cycle. Furthermore, it supports low level support for frequency hopping, and several other mechanisms required by the IO-Link Wireless protocol.
Low power operation is critical for IO-Link Wireless devices. Depending on the application, power may come from a wired 24 V supply, an inductive power rail, slip rings, or a battery.
The SoC architecture supports advanced energy management techniques, including disabling unused analog and digital peripherals, scaling down the clock speed and supply voltage, and turning off the radio when unused. The SoC’s energy mode can quickly and seamlessly be changed using the software API.
The SoC provides various features to support the future demands of applications in the IO-Link Wireless space. For instance, the hardware and software security features offered in the SoC, such as secure boot, secure debugging interface, encrypted communication, and secure key storage, which address various security pain points. Furthermore, the integrated Machine Learning (AI/ML) accelerator supports energy efficient processing in W-Devices, enabling more local computations on the edge, saving on network traffic, and off-loading resources from the backend.
For Industry 4.0 and the Industrial Internet of Things (IIoT), wireless connectivity is a must. Traditional wireless is not suitable, as it cannot both control and monitor production machinery and does not meet industrial standards for latency, reliability, and scalability.
Based on the wired IO-Link standard for factory automation, IO-Link Wireless fully meets today’s industrial communication requirements. It is ideal for applications such as data collection and feedback for Intelligent Tooling and predictive maintenance, as well as flexible, reliable communications for End-of-Arm Tooling (EOAT) in robotics; smart conveyers’ systems a sortation system in logistic areas.
IO-Link Wireless provides a proven solution for both new machines and retrofitting existing equipment, and meets the latency and reliability standards for monitoring and control use cases. It simplifies installation and supports a wide range of available IO-Link wired sensors available in the market. IO-Link Wireless is an integral component for making machines and production lines adaptive, faster, and more flexible.
Implementing IO-Link Wireless is simplified by using a System-on-Module (SoM) or wireless System-on-Chip (SoC) that can handle the wireless stack and support the fast radio switching times needed. Moreover, by integrating the necessary analog and digital peripherals, communication interfaces and a 2.4 GHz radio transceiver, the SoC can significantly reduce the footprint and cost of the IO-Link Wireless device.