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Bringing New Dimensions to HMI Implementation Without Needing Heavy Use of Resources

By Sreedharan Bhaskaran, Senior Manager, Software Engineering, Bridgetek Pte Ltd

The launch of the iPhone, a little over a decade ago, heralded a sea-change in several key elements of our everyday lives. These game-changing handsets would have a pivotal role to play in how we would forthwith interact with technology - namely through the use of touch. Though touchscreens had been in existence for many years before this, it was through this product (and the ones from other manufacturers which soon followed) that they would finally gain global traction. They have now effectively revolutionized the way in which our whole society works, and we would find it hard to live without them.

Conventional human-machine interfaces (HMIs), which used to mainly consist of mechanical buttons, knobs, and switches plus a 7-segment LED display or character matrix display unit, have been supplanted by full-color TFT-LCD screens replete with sound, video, animation and, of course, touch functionality. While processing speeds have kept pace in the application processor space, the microcontroller units (MCUs) that do most of the grunt work in commonplace electronic devices simply have not seen any significant boost in their compute capacity.

Most MCUs today are powered by the venerable 8051 core or an Arm® Cortex®-M series core and are mainly designed for control and sensing tasks. These are not equipped with graphical processing units (GPUs) like their more expensive and powerful application processor cousins. Therein lies the disconnect - having gotten used to how good touch interaction can be, people now expect the same touch, feel, and response from other equipment (whether it is of a retail, medical, or industrial nature) as they get from their smartphones. However, the MCUs cannot provide the same levels of user experience. They need help.

If the system MCU is charged with having to take care of the HMI, then some of its processing power is going to need to be diverted away from its core task. This will thereby impinge on the overall performance. Also, as displays need to be rendered and refreshed pixel by pixel, a frame buffer is needed, as well as a large flash memory to store all the graphical data. Inclusion of these components takes up space, adds to the power budget and raises the bill-of-materials costs.

Through its innovative object-oriented approach, Bridgetek’s award-winning Embedded Video Engine (EVE) series of ICs has been aimed directly at addressing the technology gap that has appeared within the HMI sector. Packed inside each of these devices is a powerful GPU, a display command processor, a JPEG decoder, an LCD controller, an audio processor, and a touch processor. When an EVE chip is paired with any standard MCU, the user experience of the system can be transformed to something closely emulating that of a state-of-the-art smartphone.

EVE is able to streamline the HMI systems by dealing with all the image and audio content required in the form of numerous constituent objects that have pre-defined characteristics (circles, squares, beeps, etc.). This means that rather than having to access all the details of the graphics or sounds that will be comprised within that HMI, each element is just assigned a simple identifier. This consequently cuts down dramatically on the data transfer involved, putting less strain on the MCU and dispensing with the need for either a frame buffer or a large flash memory. When more complex objects - such as sliders, toggles, clocks and gauges - are called for, they are all available from an expansive preprogrammed library.

Image of EVE examples in domestic appliances and retail scenarios

Figure 1: EVE examples in domestic appliances and retail scenarios (Image source: Bridgetek)

The third generation BT81X series EVE chips, with their adaptive scalable texture compression (ASTC) functionality, exhibit powerful standalone immediate mode rendering capabilities. They can accommodate display resolutions up to 1280 x 720 pixels and panel diagonal sizes up to 11”, as well as supporting capacitive touchscreens with up to five touch point detection. EVE has the capacity to breathe new life into traditional electronics hardware by updating the HMI aspect considerably. Among the numerous applications that can benefit from this technology are point-of-sales (PoS) units, domestic appliances, blood pressure monitors, power meters, set-top boxes, scientific instrumentation, elevator controls, security systems, industrial controls, GPS navigation equipment, heart rate monitors, vending machines, and home automation systems. Figure 1 shows examples of where EVE (in connection with an MCU over a SPI interface) is being implemented within: a) a leading-edge washing machine model’s HMI and; b) the smart shelves in a specialty wine store.

Another huge opportunity for more sophisticated HMI deployments lies in the automotive sector. EVE is already gaining a great deal of market uptake in relation to electric vehicle (EV) models and after-market automobile accessories. Among other places, EVE can be applied to dashboard instrument clusters, infotainment consoles, side and rear-view mirror displays, heads-up projectors, and rear seat entertainment consoles.

There is now a myriad of secondary displays, auxiliary to the central infotainment console, that are currently being designed into vehicles to make travelling more enjoyable for their occupants and give a higher degree of personalization. These can be utilized for navigation, multimedia entertainment, and connectivity purposes. In this context, EVE, when serving as an integrated HMI engine, can be paired with a relatively low-cost MCU to replace expensive application processors, flash and DRAM memory subsystems. The result is a straightforward and compact solution at a much more competitive price point.

Image of EVE applied to an automotive instrument cluster

Figure 2: EVE applied to an automotive instrument cluster (Image source: Bridgetek)

Figure 2 shows how EVE technology is already being used in automotive instrument clusters and dashboard units. Having a display-based implementation, rather than one that is mechanical, results in far greater design flexibility. The driver can easily switch between a modern or retro feel, depending on their personal preference. They can also transition from standard driving mode to sports mode view. The color scheme can be altered to reflect the driver’s particular taste too.

Image of EVE in an EV charging application

Figure 3: EVE in an EV charging application (Image source: Bridgetek)

There are also major possibilities in terms of vehicle diagnostics. Figure 3 shows EVE in an EV dashboard. Here an MCU takes input from the relevant ECUs in order to allow EVE to render key parameters in real-time (such as vehicle speed, range, motor speed, battery charge level, and energy regeneration) on the display in an eye-catching animated form through its video playback feature.

Image of automobile seat adjustment

Figure 4: Automobile seat adjustment (Image source: Bridgetek)

Figure 4 illustrates a seat adjustment HMI. Here EVE handles the graphical representation, the rendering onto the display and user touch input. It is possible to configure preferred settings - such as seat position, back rest position, backrest height, etc. These configurations can be stored into presets, which can subsequently be called up when required.

To help engineers with EVE projects, the platform is supported by a comprehensive development suite. This is comprised of EVE Screen Designer (ESD), EVE Screen Editor (ESE) and EVE Asset Builder (EAB). Providing the highest level of abstraction, ESD presents engineers with a complete workflow supporting the whole EVE development cycle. Its use of the visual programming paradigm facilitates rapid HMI construction. ESE is an intuitive HMI application targeting beginner/intermediate level EVE users. The purpose of this tool is to help users understand the usage of EVE commands. Users can construct a single static screen by dragging and dropping objects or by typing the EVE commands directly to instantiate objects on screen. The built-in EVE emulator conveys the effect of the display commands exactly as they would appear on the chosen screen size and resolution. The EAB application is intended for users to convert all the HMI assets (such as images, audio, video, font data, etc.) so they can be combined into an EVE compatible format.

The EVE ecosystem (with its chips and supporting toolchain) offers the means via which to create lively, colorful, and rich touch-enabled HMIs that lead to more satisfying user experiences. What is more, it does this without the need to specify an expensive application processor IC. The scope of this technology is now being recognized in a broadening variety of industry sectors - including an increasing prevalence in the automotive arena.

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About this author

Sreedharan Bhaskaran, Senior Manager, Software Engineering, Bridgetek Pte Ltd