Driving brand recognition with enhanced MCU graphics capabilities
30 August 2017
Brand is everything when it comes to selling products for customers to buy – and more importantly – continue to buy. Anything with a screen is expected to have a polished look and feel and be easy to use. With the rise of the Internet of Things (IoT), more and more simple devices now feature interactive display screens, presenting design challenges for engineers.
This article originally appeared in the September 2017 issue of Electronic Product Design & Test; to view the digital edition, click here – and to register to receive your own printed copy, click here.
Traditionally, microcontrollers (MCUs) have not had the capabilities necessary to power these applications, but switching to more advanced microprocessors (MPUs) brings additional costs and design complexity. This article discusses how hardware manufacturers are increasingly recognising the need to offer more advanced graphic capabilities for MCUs.
The inclusion of a graphical user interface (GUI) in embedded designs serves both functional and aesthetic purposes. Often one of the most overlooked and valuable functions of a graphical interface is the communication of brand identity. This set of visual characteristics represents the brand and company, and includes the logo, colour usage and fonts. Brand identity uses graphical elements to convey the personality, mood and/or values of a company, contributing to positive brand recognition.
Not prioritising positive user experiences with your company’s brand identity – perhaps by settling for static, cluttered or antiquated GUI designs – can prevent users from being drawn to seek out repeat experiences with your product. This persistent search for an anticipated positive experience is called preference, and many end users with preferences for specific brands are willing to pay a premium for them. This in turn increases profit for the sought-after brands – with brand recognition, combined with positive user experience, driving profit.
Your company’s marketing department most likely spends considerable resources educating customers about its products and the user experience they should expect. There are many different channels they might use for this, including advertisements in print and online trade publications, social media, emails, or even broadcast commercials. Companies who profit the most from compelling brand identity also pay special attention to how the brand is communicated in product design, especially via its HMI (human-machine interface).
In the extreme, creative and accurate branding of your UI (user interface) acts like your company’s billboard – located on every product it sells. MCUs for advanced graphics
Traditionally, MCU applications that needed to include GUIs used either external graphics controllers or a static direct-drive DMA-based graphics scheme to push full frames out to displays up to WVGA (800x480). External graphics controllers are an extra component in the embedded design, leading to undesirable additional cost, board size and design complexity.
Graphic needs, such as large colour depth, colour format conversion, alpha blending and animation, typically drive embedded designers toward microprocessors (MPUs). MPUs generally offer higher performance than MCUs, but also bring higher levels of complexity.
Switching from an MCU design to an MPU design also requires knowledge of software and hardware paradigms that may not be readily available within your embedded design team.
Fortunately, recent advancements in MCU graphics technology have enabled capabilities that would otherwise have only been possible with MPUs – but without having to invest in new hardware and software design methodologies. While certain applications still absolutely require the use of an MPU, many design engineers can benefit greatly from new advancements in graphics capabilities now available with MCUs. Let’s discuss how applying some of these advancements can drive brand recognition into your next GUI-based embedded design.
Integrated graphics controllers
Perhaps the most central component of a graphics-enabled microcontroller is the integrated graphics controller peripheral. In its basic form, it’s responsible for taking image data from memory and putting it on the display. This function would be assigned to a Direct Memory Access (or DMA) unit inside the microcontroller.
In truly graphics-enabled MCUs, however, an integrated graphics controller will offer more features and options to help the application look as attractive as possible. There are three main parameters used to describe the capabilities of a graphics controller in an MCU: colour depth, image size and frame rate. Colour depth is explored below. Image size is simply the height times the length of the display in pixels. Frame rate is the rate at which the whole picture on the display is redrawn. The higher the frame rate, the smoother the transitions of the image appear to the end user. Smoother transitions make the product appear to be of higher quality, positively impacting user experience.
Limitations of typical MCUs, such as pixel clock and memory availability, often result in trade-offs in the choices among these three elements. For example, a rich, vibrant colour depth may necessitate the choice of a smaller-than-desired display in order to fit the application into available MCU memory. Recent advancements in design and manufacturing technology have driven substantial increases in available in-package memory, and this has significantly increased the capabilities of graphics MCUs. To appreciate the importance of large amounts of integrated memory, let’s discuss colour depth.
Colour depth is defined as the number of bits used to indicate the colour of a single pixel in a bitmapped image. The more bits used to describe a colour, the more subtle the differences in colour from one value to the next. New advancements in the amount of MCU memory are enabling regular usage of 32 bits of colour depth: this translates to approximately 16.7 million different colours. Rich, deep colour is important to customer experience and branding in two very significant ways.
The first reason that rich colours are important correlates with how your end users interpret the presented image. If your application relies upon realistic representations of photographs or art, then your end users will judge the quality of your device based on how closely the image matches the object being represented, whether visually or from memory.
The second reason has to do with brand recognition. Colours play a vital role in helping customers identify a brand. Not only are they very specific (Pantone® has built its entire business based on this concept!), but they also help end customers identify whether a product is real or fake. Not being able to accurately represent a brand’s colour could damage the user’s perception of the quality of the device they are using.
Using 32 bits of colour (24 bits of actual colour description, plus 8 bits of transparency level, also known as alpha channel) carries a heavy price for an application’s memory usage. For a WVGA (800x480) display, 32 bits of colour translates to approximately 1.5MB of memory needed just for one buffer, representing a single frame to be displayed.
This level of colour depth is important when representing photographs or artwork, as well as for applications that provide web access where colour presentation from a third party is unpredictable and varied (think maps, images and video). Because microcontrollers have typically contained no more than 512KB of on-chip memory to hold image buffers, external memory would be required for such applications.
But new advancements in die design, packaging and manufacturing have led to huge gains in on-chip memory. The PIC32MZ DA from Microchip, for example, features 32MB of DDR2 DRAM in a single package, with a fully-enabled graphics MCU. There is therefore no need for external buffer memory to be added. This reduces cost, complexity and the overall size of the design. When combined with a 3-layer graphics controller and a fully featured 2D graphics processor, the PIC32MZ DA is one example of the advancements in highly integrated graphics controllers available to embedded designers for GUI-based applications.
Graphics development tool basics
The importance of a good set of design tools, tightly integrating automation with flexibility, should not be overlooked. To hit the proper tone when creating user interfaces that drive preference, it’s important to have tools that enable the designer to prioritise content creation, rather than mundane code debug and needlessly iterative programming. One approach to GUI design that can propel embedded coders to UX experts is WYSIWYG (‘What-You-See-Is-What-You-Get’). The intent of this approach is for the tool to enable the designer’s creation of a UI in their tool’s design space to look exactly like it will when pushed to the hardware platform. When combined with other tools that automate the creation of drivers for non-standard graphics panels, this enables a high-end design experience, while eliminating time spent on coding and debugging the user interface. One example of such tools is the MPLAB Harmony v2 Software Framework from Microchip. MPLAB Harmony brings industry-leading capabilities, including design entry, memory management, events and display drivers that are tightly coupled to existing tools, including code generation, debugger, MPLAB X and MPLAB Harmony Configurator.
Paying special attention to the way that embedded user interfaces drive positive experiences – and draw users to return again and again – will reap profitable rewards. Fortunately, recent advancements in MCU graphics and memory technologies are enabling embedded designers to up their GUI development game, without having to learn new and complex software and hardware design paradigms often associated with MPUs. Making the right choices in architecture and toolsets can make driving brand preference and positive user impressions easier than it has ever been before.
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