Industry Article

Choosing the Right MPU for Display and Camera-related Industrial HMIs

February 10, 2022 by Yasushi Iwase, Renesas

In this article, learn about the different considerations that go into choosing the right microprocessing unit (MPU) for industrial human-machine interface (HMI) applications.

HMIs have significantly evolved since the standard was a panel of lights, dials, and manual switches. With this evolution, there is a demand for HMIs with advanced display and/or camera capabilities, including 2D/3D imaging and image recognition, many of which involve HD (high definition) requirements, as can be seen in Figure 1. 


Figure 1. Many HMIs now involve a camera, image, and video technology, such as the high-performance system outlined. The necessary functionality can be supported through the choice of an MPU. Image provided courtesy of Renesas


Achieving high performance, reliability, and efficiency, along with a short time-to-market, for such applications is critical to staying competitive in such markets. For that reason, engineers tasked with designing HMIs may consider embedded MPUs for handling display and camera-related functionality.

In this article, learn how MPUs can benefit common HMI applications with examples from Renesas.


HMI Applications

There are several applications and industries that depend on HMIs to provide high-resolution image and camera functionality:

  • Commercial: home security, doorbell systems, multifunction printers, building automation control panels, white goods
  • Business: digital signage, KIOSK/POS terminals, business displays, barcode scanners, authentication entrance system, office equipment, handwriting recognition
  • Industry: industrial signage, CNC equipment, handheld terminals, measuring equipment, inspection devices, diagnostic panels, industrial panels
  • Medical: medical display, patient monitoring systems

These applications can be significantly enhanced using an MPU solution. For example, choosing an MPU with a fast, powerful central processing unit (CPU) can speed up the image and/or video processing of security products, patient monitoring systems, industrial panels, and KIOSK/POS terminals, not to mention signage and digital displays. 

Another example of enhanced image processing capabilities includes dedicated image processing and the use of a graphics processing unit (GPU), further improving performance and speed for inspection devices, barcode scanners, authentication control panels, home security, and multifunction printers. 


Choosing an Embedded MPU Solution for HMIs

When choosing an embedded MPU solution for an HMI, certain key characteristics should be considered first: 

  • CPU performance, processing speed, and memory
  • Dedicated image processing software
  • Reliability
  • Security functions
  • Long-term software support
  • Availability of development kits


CPU Considerations

CPU performance is critical while searching for an embedded MPU solution, with memory and processing speed also playing an important role in factors such as video resolution and 2D/3D capabilities. 

ARM-based CPUs are a common option and are available as either single or dual-core. ARM Cortex-A CPUs are well-adapted for HMIs because of their performance and low power consumption. For example, some 64-bit Cortex-A CPUs offer speeds up to 1.2GHz.

Selecting the right processor should balance performance against image processing speeds. While dual-core CPUs are faster because they allow more processors to run simultaneously, for example, they are not always the right option. If the software does not support multi-core technology, a dual-core option will not add speed or processing benefit. 

An example of an MPU with supporting software is shown in Figure 2.


Figure 2. A block diagram of the RZ/G2L MPU. Image used courtesy of Renesas.


Image Processing Software

Dedicated image processing software, such as the video codec, video engine, and graphics engine, is also important. It can process graphics and handle compression/decompression (i.e., H.264 and H.265) without imposing a load on the general software. This image processing software can include specific features for advanced HMI features, such as 3D graphics and high-resolution video. 


Error Correction Codes for Reliability

Reliability, which is especially crucial for mission-critical applications, includes features such as built-in error correction code (ECC) for internal and external memory. ECCs serve an important purpose in data transmission because they allow for message recreation even if some of the bits have been erroneously flipped.


Hardware-based Security

Key security functions include secure boot, debugging, and, for Arm CPUs, Arm TrustZone. Arm TrustZone was created specifically for embedded hardware, simultaneously running a secure OS (operating system) and a less secure OS on the same core to promote security. 


Long-term Support Infrastructure

In some HMI applications, industrial and infrastructure equipment manufacturers expect long-term software support because of the equipment’s lifespan. This type of long-term support is provided in some MPUs (e.g., Renesas RZ/G series) through the Civil Infrastructure Platform (CIP) with Super Long Term Support (SLTS) Verified Linux Package


Figure 3. A block diagram overview of the RZ/G2 reference board, highlighting the CIP SLTS kernel. Image provided courtesy of Renesas.


CIP is an open-source base layer for industrial-grade software and is specifically designed for the long-term management of infrastructure systems. The SLTS Linux kernel, in particular, ensures more than 10 years of support.


Renesas RZ/A and RZ/G Series for Industrial HMI

The Renesas RZ product series of 64- and 32-Bit Arm-based MPUs include two series that are options for industrial HMIs: the RZ/A and RZ/G series. 

The RZ/G2L, RZ/G2LC, and RZ/A1H are intended for display-related HMI applications, while RZ/A2M is recommended for camera-related HMI applications. 

The RZ/A2M has embedded with the DRP (Dynamically Reconfigurable Processor) technology that accelerates image processing with embedded artificial intelligence and is suitable for object recognition applications.

In addition to the Cortex-A CPUs and available memory, both of these MPU product lines provide dedicated image processing software, reliability, security functions, and long-term software support, which, as mentioned previously, can be important to consider when choosing an MPU for HMI applications.

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