Customers and machine operators are placing increasing demands on the operation of industrial applications - characterized by the familiar use of smartphones and tablets. Manufacturers of industrial control systems and human machine interface (HMI) devices are therefore called upon to act in order to keep pace with competitors and new market trends.

When implementing HMI devices, there are different user requirements, resulting in different operating concepts. For example, a display controller can simply be used for visualization, i.e. the display unit only shows the graphical data of the system. An additional touch system connected to the display supplies the coordinates for operation to the system. These classic HMIs are only concerned with displaying and entering data. The control tasks of a machine or device are performed by a separate unit and displayed by the connected display unit.

However, it is becoming increasingly common for an HMI to take over the complete control of devices and systems in addition to visualization. In this concept, one unit performs all the tasks of the system. These solutions are usually less expensive and also more energy-efficient, as only one CPU is used.
Due to the increased requirements, most CPU manufacturers adapt their ARM-based processors so that many interfaces such as graphics, Ethernet, CAN FD, ADCs, SPI, I²C and digital IOs are already integrated into the CPU. With this variety of interfaces, most system requirements can be implemented without major additional effort.

ARM-based CPUs

One trend in ARM-based CPUs is to integrate graphics processing units (GPUs) to support the computing cores. These enable more demanding visualization tasks, starting with a single display and extending to multi-display solutions with a resolution of up to 4K.

In multi-display applications, the increased performance of GPUs means that two to three displays with different image content and different resolutions can be connected directly to the CPU. Integrated graphics interfaces such as MIPI DSI, LVDS, HDMI and DisplayPort ensure flexibility when connecting the display units. In most cases, a display including touch is connected directly to the CPU's LVDS. A second display is often made possible via HDMI. The advantage here is that this display can be placed several meters away so that the status of larger machines can be viewed from several locations, saving employees valuable time. One or more GPUs support the cores integrated in a CPU and thus significantly increase the performance of the entire unit: the cores are available for the control tasks and the graphics application is outsourced to the GPUs specifically designed for this purpose.

Universally applicable

An intuitive and clear operating concept not only makes operation easier, but also reduces the frequency of errors.

© TQ Systems

Thanks to the large number of directly available interfaces and the possibility of freely selecting the operating system depending on requirements, ARM-based processors can be used universally. Due to good application support for industrial controllers and HMI devices by CPU manufacturers, more and more devices are being developed on the basis of this architecture.

Operating systems (OS) specially adapted to ARM CPUs are used - in addition to Linux, Android and QNX, which are among the most frequently requested and used operating systems. Microsoft will again offer its support for high-performance ARM cores based on Windows 10 IoT. This support is driven by the partnership between Microsoft and NXP and will initially support the 'i.MX 8M' family. This is intended to provide compatibility with Windows applications and graphics functions for cost-effective and energy-efficient systems. As a result, applications such as NET Core, .NET Framework, WPF, WinForms and newer frameworks such as WinUI and UWP can be used.

The control requirements must be taken into account when selecting the operating system, as well as any necessary support for third-party software. An OS specially adapted to the platform has the advantage of providing users with optimum performance. This also allows complex control systems with attractive graphics performance to be implemented without the large overhead of an operating system.

The right architecture

In addition to selecting an OS, every user should consider whether there are special requirements in terms of safety, security or machine learning when selecting the architecture. There is also hardware and software support for arm-based HMIs.

A graphical user interface (GUI) is used to display the application. Proprietary interfaces and operating systems exist for this purpose. Popular development tools for interfaces are QT and Storyboard from Crank. They can be used to create an interface according to the application requirements, regardless of the operating system. The necessary touch technology must also be supported to match the GUI and the desired usability. In older HMIs, touchscreens with analog resistive technology were used. A newer technology is projected capacitive touch (PCT). Depending on the manufacturer and its driver support for the OS used, multi-touch applications can also be implemented depending on the GUI.

CPU modules often offer the advantage that the BSP support (Board Support Package) is better than the BSP provided by the CPU manufacturer. Thanks to the investment made by module manufacturers, customers do not have to do any work themselves to implement good support for graphical interfaces that also support touch. This reduces the investment in creating the operating system. With this technology, the operation already familiar from smartphones or tablets can also be integrated into industrial systems, medical devices, smart home applications and other scenarios.