“Human Machine Interface (HMI) can be seen everywhere, and in recent years has become the subject of a large number of applications. While consumer products bring enhanced connectivity and a more immersive user experience through innovative HMI design, industrial products continue to use physical interfaces, which usually rely on small displays or simple LEDs to implement HMI , And use simple electromechanical switches or buttons as the main interaction method.
Human Machine Interface (HMI) can be seen everywhere, and in recent years has become the subject of a large number of applications. While consumer products bring enhanced connectivity and a more immersive user experience through innovative HMI design, industrial products continue to use physical interfaces, which usually rely on small displays or simple LEDs to implement HMI , And use simple electromechanical switches or buttons as the main interaction method. If the device has a local connection function, cables and physical connectors are usually used to realize the physical interface. It can be seen that improving the user experience by changing the interconnection mode of industrial products has huge potential for development. In an increasingly complex and complex market, this provides opportunities for innovative suppliers to create differentiated products.
But we should also see that industrial equipment HMI will bring huge challenges to designers. Because product design specifications may need to follow standard guidelines, equipment may be restricted by physical size, and larger equipment may need to be equipped with control devices. Products used in industrial environments represent a vital capital investment, which means that even if their robust local interfaces are affected by various stress factors, they are still expected to be used reliably for many years. Safety is another important consideration. When connected to other devices (such as computers), the product must maintain safe operation, which usually requires electrical isolation on all external ports.
Wireless technologies such as Bluetooth, driven by modern standards, provide designers with new tools that can help them change the user experience of industrial equipment. In addition, compared with traditional wired connection solutions, the man-machine interface based on Bluetooth can save costs.
Bluetooth provides an excellent user experience
By using Bluetooth with industrial equipment, end users can wirelessly connect any Bluetooth-enabled device to their device, thereby eliminating the physical dependence on specific types of connectors. Currently, almost all devices (including smartphones, tablets, and laptops) support Bluetooth, which clearly shows the platform independence of the technology. This is extremely beneficial to end customers, because they can no longer be limited to using physically and electrically compatible customized devices, and even competing operating systems and product brands can use Bluetooth to achieve compatibility with each other.
With the improvement of Bluetooth flexibility, developers can use mobile applications to freely create more innovative and intuitive graphical user interfaces, without being restricted by device size or physical buttons. An easy-to-understand user interface can not only provide a more beautiful experience, but also reduce user-related errors. Different from the use of complex buttons in traditional designs, intuitive screens can better Display functions and provide users with clearer instructions. In this way, the time required to train operators to learn to use the new system can be reduced, thereby providing additional benefits to end customers.
When access to equipment and data is simplified, new data-driven application cases and functions can be developed. This includes reducing the time required to reconfigure device settings, or adding predictive maintenance (achieved by accessing and analyzing operational data) and other functions. These operations can be done over-the-air (OTA) without affecting normal operations. Moreover, by introducing a cloud connection, new settings can be centrally distributed directly from the managed database to solve operational errors, without the need for the operator to program locally.
Removal of the physical connection saves costs
Compared with the traditional man-machine interface, Bluetooth can greatly save costs. In the industrial equipment market, electrically isolated serial ports are one of the most common interface technologies. Compared with isolated serial ports, the bill of materials (BOM) cost of a system-in-package (SiP) Bluetooth module can be reduced by up to 48%. If the device has a local LCD Display and electromechanical components such as switches and buttons, the cost difference will become even greater.
Reduced maintenance costs can further save overall costs. When using Bluetooth, the user does not need to touch any mechanical components. Therefore, there will be no failures related to these components, thereby reducing the product return rate. For the end customer, the wireless interface eliminates the possibility of mechanical failure due to accidents such as connector damage, thereby avoiding expensive maintenance costs.
Moving to wireless interfaces can improve future scalability and security
The expected service life of industrial equipment is many years, which greatly exceeds the typical service life of most consumer products. During the use of industrial equipment, developers will inevitably develop new functions to meet the ever-evolving market demands. But adding new features to industrial equipment can be a tedious process because they are usually located in places with restricted physical access or places that require a lot of effort and cost to access. However, by using OTA firmware updates, wireless technology provides a simpler upgrade method. For end customers, equipment upgrades provide them with a new way to continuously utilize their initial investment, and equipment manufacturers can also implement new business models and focus on selling optional software features, thereby extending the revenue cycle of their products .
Like all software, mobile applications also need to be maintained, and with it is the continuous evolution of the underlying operating system. When selecting a Bluetooth supplier, device manufacturers should pay close attention to the supplier’s commitment to maintaining the Bluetooth protocol stack and mobile application library. When a new major version of the operating system is released, vendors who can provide timely and tested library updates will be more popular.
Industrial systems are increasingly becoming the target of cyber attacks. In addition, there are more and more relevant regulations that already exist or are being planned. For example, one of the most recent regulations is SB327 in California, USA, which sets rules for Internet-connected devices. Although Bluetooth itself includes security features (such as encryption), it is not enough to rely solely on the security provided by the standard itself. Device manufacturers should ensure that their Bluetooth suppliers have strong security capabilities, and their wireless system-on-chip (SoC) and modules should include advanced features such as secure boot to prevent unsigned firmware from being executed on the device.
Cloud connectivity has become the mainstream of the Industrial Internet of Things. By combining Bluetooth with modern mobile operating systems, a secure cloud connection becomes much easier than updating traditional desktop applications. In addition, cloud applications make software update delivery more centralized. As the Industry 4.0 wave sweeps across different vertical markets, the demand for cloud-based solutions is expected to continue to grow.
Reducing the number of electromechanical components improves reliability
For buttons or displays, how often do they fail on average? How many times can the physical connector be plugged and unplugged without failure? For devices with a physical user interface, these and many other issues must be considered by designers. In contrast, wireless technology is not affected by mechanical stress, and the removal of physical interfaces means that one less variable can be considered when designing an enhanced industrial environment.
Any physical connection to the device requires an opening in the device housing. Since industrial equipment is usually deployed in a variable and harsh environment, we must protect such openings from dust, water splashes, and other factors that may damage the equipment or parts. After using the Bluetooth connection, the device casing can be completely sealed. If LED indicators are used, they can be placed in the housing and viewed through a translucent barrier.
The increased reliability achieved through the use of Bluetooth can save actual costs for device manufacturers and end users, including:
It takes less time to design a housing that can withstand harsh environments, thus shortening the time to market.
There are fewer electromechanical components, and they are usually very expensive compared to semiconductor devices, so removing these expensive components from the design can also increase gross margins.
The total cost of ownership (TCO) for the end user is lower because the simplified human-machine interface using Bluetooth requires less maintenance.
As we all know, in an industrial environment, a large number of machines and equipment generate radio frequency (RF) noise, which poses a challenge to wireless technology. Because Bluetooth uses frequency hopping technology, it can better resist radio frequency interference (RFI) from various sources. This is an important consideration because many applications and technologies use the 2.4GHz ISM band. Interference to one or more channels will not completely interrupt the communication. Therefore, Bluetooth is suitable for industrial environments.
Precautions for Bluetooth connection design
There are multiple ways to add Bluetooth connectivity to the application. If the developers themselves have Bluetooth design expertise, embedded firmware and mobile development team, and the resources required to design through the RF certification process, then it is an economical for them to design Bluetooth SoC solutions into the application Efficient approach.
However, for companies with only a small amount of expertise in wireless product design, pre-integrated and pre-certified wireless modules are their ideal solutions. Choosing an integrated module with pre-certified RF and hardware allows these companies to spend less time adding wireless technology to their designs.
The benefits of choosing a Bluetooth module include:
Integrated antenna selection minimizes the need for RF expertise
Pre-certification, avoiding lengthy and expensive RF certification work
Out-of-the-box performance that can meet most needs
Pre-programmed modules provide many advantages
Using the module to add a Bluetooth connection still requires developers to have a certain degree of familiarity with the Bluetooth protocol, and at the same time understand how to use the vendor’s Bluetooth protocol stack and related APIs. In many Bluetooth applications, developers must also create an embedded host connected to the Bluetooth Connection Coprocessor (NCP). The communication link from the host to the NCP usually exposes the low-level control of the NCP, and the embedded host must invest a lot of on-chip resources to maintain the buffer and monitor the status of the NCP Bluetooth link. In order to meet these needs, engineers may be inclined to choose an embedded host whose performance exceeds the application specifications, which will make the cost higher than the actual cost of the application. MCUs whose performance exceeds the application specifications may also generate more power consumption.
However, evaluating the correct solution itself does have many challenges, because developers must explore all possible application scenarios and evaluate how each application scenario may affect functionality. It is also necessary to test as many application scenarios as possible to see whether the application functions work as expected, and then to troubleshoot or repair them when there are faults or vulnerabilities. This may involve complex debugging across hosts and NCP development environments.
Fortunately, the use of pre-certified modules can further simplify Bluetooth design. The pre-certified module is pre-programmed with Bluetooth firmware to provide out-of-the-box connectivity. The benefits of pre-programmed modules include:
Can access the Bluetooth protocol stack and pre-programmed embedded application firmware, without the need for firmware development
A production-level test infrastructure is available for testing the protocol stack and firmware that have been configured by the module supplier
Built-in support for firmware updates and boot loading, which can support future security updates, bug fixes and robustness improvements
Establish a connection between the embedded system and the mobile phone
As mentioned earlier, the advantages of using Bluetooth include access to a variety of potential user interface design resources, especially the convenient use of a tablet or other form of mobile device as a controller. However, the development of mobile applications is a specialized field. Therefore, as an element of product design, manufacturers usually need to hire external development services for them. There are relatively few developers who know how to correctly write application code that can be connected to the low-level Bluetooth APIs on the iOS and Android platforms, and services that provide such expertise can be very expensive. Companies may also need to hire different experts for each platform, which will increase the upfront costs and bring time-consuming project setup difficulties.
Using the wireless interface library developed and provided by the module supplier to start the development of mobile applications can significantly reduce the threshold for mobile application development. A wireless interface library designed for connecting with selected pre-programmed modules provides:
Abstract interface of the core Bluetooth API for multiple mobile operating systems
API dedicated to optimize the interface control of embedded modules
Cloud-to-module path for firmware update
Silicon Labs’ Bluetooth Xpress products combine these development optimization features to provide a simplified embedded-to-mobile connection.
Bluetooth Xpress products combine firmware, hardware, and mobile development optimization functions. The Bluetooth Low Energy 5 (Bluetooth Low Energy 5) module it provides can reduce the development time required for an application from concept to prototype to only one day. Bluetooth Xpress products also include the Xpress framework for mobile application development, which significantly reduces the development time required to add Bluetooth connectivity to mobile applications.
The main functions of Silicon Labs Bluetooth Xpress modules (BGX13P and BGX13S) include:
An out-of-the-box, pre-programmed, pre-certified Bluetooth solution that supports Bluetooth 5 features, including 2M PHY and long-distance PHY
Set up and control the onboard wireless protocol stack through the high-level Gecko OS Xpress Command API
Baud rate, flow control, general-purpose input and output (GPIO) and Bluetooth performance parameters can all be configured for the specific needs of the application
An I2C main interface, which can realize Bluetooth low energy wireless communication to I2C
Input pin monitoring, support automatic digital logic conversion response
Only a small amount of resources from the main processor are required, allowing developers to add wireless connections to any MCU
Provide PCB and SiP packages at the same time
One-stop design support
Supports security functions and firmware updates
The functions of the Bluetooth Xpress module in three application scenarios:
1. BGX13 to smart phone-In this application scenario, BGX acts as a peripheral device that can be discovered and connected by a smart phone.
2. BGX13 to BGX13-In this application scenario, one BGX acts as a peripheral device that can be discovered and connected, and the other BGX acts as a control terminal to perform scanning and connection. After connection, BGX13 can work in data stream mode, that is, data bytes are transmitted between two points without overhead data stream; it can also work in command mode, in which Bluetooth Xpress commands can be executed remotely.
3. BGX without embedded host-this application scenario is a variation of application scenarios 1 and 2. In this application scenario, the on-board Bluetooth Xpress functions such as input pin monitoring, event notification, and Bluetooth to I2C bridge are sufficient to assume all the responsibilities of the embedded host processor.
In these defined application scenarios, the BGX flow control signal can indicate the buffer status, and can also be used to indicate whether the embedded host can transmit data.
Figure 1: The Bluetooth module can be deployed in a variety of ways to meet the specific needs of the application
Bluetooth Xpress configuration and communication
The system controls the pre-programmed function of Bluetooth Xpress through a configurable command interface at runtime, and its default settings are stored in non-volatile memory. The interface can be used through the serial interface pins, and can also be implemented wirelessly through the Bluetooth interface. It acts as a high-level network coprocessor.
In most operating states, Bluetooth Xpress acts as a zero-overhead data stream from Bluetooth to the serial port. For example, the Bluetooth Xpress module can send a signal to the embedded host by changing the state of the port pins to indicate that the connection has been established. At the connection point, the RX and TX pins of the serial interface act as a bidirectional data interface, which has the same function as a wired serial link. Data can be written from the host to the RX pin of the Bluetooth Xpress module, and then Bluetooth Xpress transmits the data byte by byte through the BLE link. On the other side of the BLE link, either the smartphone receives the data and provides a buffer to the mobile application, or another Bluetooth Xpress module receives the data. The Bluetooth Xpress module that receives the data will then send the data out through its TX pin, which will be received by the remote embedded host.
Use Bluetooth in HMI of Industrial Automation
Many industrial automation equipment use serial protocols for local configuration and diagnostic ports. This technology is well known and widely supported. Although many of these physical serial ports are rarely used in modern laptops, the virtual COM port driver allows the use of USB instead. Now, this traditional architecture provides fertile ground for alternative Bluetooth-based human-machine interface products.
Figure 2 shows a traditional industrial automation equipment that uses a serial interface to support local configuration and diagnostic ports. The cable interface will bring many challenges, these challenges will increase the cost of the product, while reducing the convenience, and have a negative impact on the overall user experience.
In order to ensure user safety, the cable interface must be electrically isolated from the remaining circuits of the industrial automation equipment. In addition, the cable interface requires a chip to provide the RS-232 driver and the actual physical serial port. These and the required passive components increase the bill of materials (BOM) cost of the equipment and require more PCB area.
The cable interface may also present physical access challenges. If you install the device in a hard-to-reach location, you may not be able to connect the cable to the device. This means that the device can only play part of its functions and advantages.
Figure 2: The traditional method of product design using a serial port with electrical isolation
Now look at the example in Figure 3, which shows the same industrial equipment using the Silicon Labs BGX13 Bluetooth Xpress module, which is designed for scenarios where cables can be easily replaced. The application CPU can continue to use the existing UART interface, because Bluetooth Xpress supports the transmission of serial data through the Bluetooth link. Under such a design, the designer does not need to master any Bluetooth knowledge in advance, so the time and risk associated with Bluetooth integration can be greatly reduced. All intelligent functions are built into the protocol stack and application firmware running on the module. Bluetooth Xpress also supports SPI interface, which makes it more suitable for this application.
Bluetooth Xpress modules have different dimensions, the smallest SiP package size is only 6×6 mm, which is very suitable for space-constrained applications. Because the module also includes an antenna, designers have more flexibility when placing the module on the circuit board.
Figure 3: Application example using Bluetooth instead of cables
The important point is that the use of Bluetooth for the human-machine interface will not replace or affect the use of fieldbus communication. This method maintains backward compatibility with previous generation equipment, which is something that many industrial automation equipment customers value.
By removing electrical isolation, serial interface drivers, and physical connectors, BOM can be simplified, and product costs related to cable interfaces can be reduced by as much as 48%. Removing the physical connector can also avoid the need to open the housing so that the user can access the connector. If the connector requires additional protection against environmental conditions such as dust or humidity, greater cost savings can be achieved, because these protection measures will no longer be required using a Bluetooth-based solution.
This architecture allows users to wirelessly connect multiple devices from one location without physical access to the devices, which can improve functional security. In this way, the device configuration can be modified more flexibly and the diagnostic data stored in the device can be downloaded for analysis and troubleshooting. By default, Bluetooth also includes data encryption and hashing algorithms, which can add another layer of protection against cyber threats.
As mentioned above, the mobile application framework included with Bluetooth Xpress products can greatly simplify the design of Bluetooth integration. By abstracting the low-level Bluetooth function and making it accessible via API, it can help device manufacturers achieve faster time to market, because they can use high-value development work to add features to their products instead of learning Bluetooth on Android or iOS Aspect characteristics. Mobile applications also support cloud connectivity, which can be used to provide new cloud-based products.
Essentially, Bluetooth has nothing to do with hardware. Now, more and more devices support Bluetooth connection, which means that it is an effective abstraction layer between low-level functions and high-level control and monitoring functions.
Bluetooth has many benefits in an industrial environment. As an alternative cable technology, it has proven to be a reliable solution in HMI application design. Using a module like Silicon Labs’ Bluetooth Xpress to add Bluetooth connectivity to a device can save a lot of measurable costs, and it does not require the expensive components required for physical cable interfaces, which can significantly reduce costs. At the same time, the use of mobile applications can provide a more user-friendly interface, and the functions can be further expanded by connecting the application to the cloud.
With ready-made APIs that are easy to integrate at the board level, link level, and mobile application level, the Bluetooth Xpress product portfolio becomes an ideal solution to replace the existing serial communication cable interface. Using pre-certified modules can achieve faster time to market, because device manufacturers no longer have to worry about the time-consuming certification process, but can focus on marketing to make their devices successful.