Increasingly recognised as a key differentiator by which OEMs can set their products apart from those of the competition, the human machine interface (HMI) is a vital part in any modern electronic design. It is through this that interaction with the system will occur and is what will predominantly define the user experience (UX). Consequently this aspect needs to be given considerable attention.
For the vast majority of systems, the HMI now comes in the form of a touch-enabled display. These have many attributes that make them more appealing than the mechanical switches and keypads of the past - in terms of better reliability, flexibility, overall aesthetics and more straightforward execution of designated tasks.
Because of these operational benefits, plus the enhanced UX that can be derived from them, touch-based HMIs have seen traction in all manner of products over the last decade - including everything from household appliances, point-of-sales (PoS) units, vending machines and handheld electronic devices, through to industrial control equipment. They are being fitted into outdated legacy designs in order to upgrade them, as well as in brand new projects.
When looking to implement an HMI, engineers are presented with two principal options. Firstly, they can look to design a display from scratch using numerous discrete components. Conventional thinking has tended to favour this approach - mainly because it is perceived as being more cost effective and also it appears to be a way for product differentiation to be realised. Unfortunately, neither of these apparent benefits is actually that true in this context.
To begin with there are a multitude of additional costs involved that are not normally taken into account when going down the discrete route. A suitable display, accompanying controller IC, touch controller, frame buffer and other memory reserves all have to be found, then fitted together into an acceptable PCB form factor. Several iterations may be needed before an optimal structure is found. This subsystem will also need to be interfaced with the host microcontroller of the main system. Then heatsinking must be put in place, and a bezel added, followed by extensive function and compliance testing, etc. This is a lot of work to get through (5 or 6 months at least) even before starting to think about the look and feel of the graphic user interface (GUI) that will be rendered on the display.
As well as specifying, sourcing and then subsequently integrating all the constituent components, there will be other supply chain related problems that could arise - component shortages, obsolescence and suchlike. Alongside the hardware issues, there is the software/firmware to take care of - this entails creating the relevant libraries and drivers to support the display, writing all the additional code, then debugging it …. and that clock is still ticking!
Next, there is the whole matter differentiation. As already mentioned, the HMI definitely offers a way of achieving this - with either a good or bad UX often being the deciding factor when purchasing an item of electronics equipment. However, this is not something that will be massively affected by what goes on at the component level. It is more likely that the way the HMI is laid out, how easy it is for even an inexperienced user to navigate their way around it, and the strength of its visual impact will be of importance.
Given that time is such a precious commodity, it is advisable to use it wisely. If engineers do not have to concern themselves with designing the display, then there are various other tasks that they can devote their time to. It should also be noted that in many cases, the engineering resource available is limited. This may not just be with regard to team size, but also in terms of its scope of knowledge. If a company makes a particular piece of equipment then most of its technical abilities will relate directly to this, not HMI development.
Companies have invested heavily in the recruiting and training of engineers, so they want to make the most of these individuals’ talents and maximise their productivity. Carrying out a discrete HMI design is simply taking them away from their core competency. By offloading the low-level design, the time and effort that would have been expended here can be channelled into areas where they can make a real difference.
For these reasons the second option - employing intelligent display modules - is becoming increasingly valid. By doing this, many challenges presented during early stage development can be circumvented and time saved. Furthermore, if the modules are complemented by a comprehensive integrated development environment (IDE) then GUI construction can be facilitated too, with drivers and many key graphical elements all readily available to utilise. An applicable analogy here would be; suppose that you were designing a website on WordPress. It wouldn’t be necessary to learn about the many nuances of HTML, as all of that will have already been done for you. Instead you could focus on the content - which is what will attract potential visitors. Use of intelligent display modules will mean that more sophisticated features and functionality can be applied to the HMI system in software that will enhance the UX, rather than time being taken up with lower level design it can be allocated to things that have far more value - making the graphical content compelling and the GUI’s operation as intuitive as possible.
Taking the modular route has other advantages too. As well as accelerating development cycles in single projects it also facilitates a more versatile platform-based strategy, so that rather than starting from scratch again with future projects, the foundations are already there. By way of an example, take an engineering team that are developing a range of different products, each occupying a distinct price point. There might be an economy model that just has basic functionality, then a medium level model with some additional features included and finally a high-end model with even more. Starting with a display module as the common basis, each model prototype would be much quicker to create.
Though discrete design means the bill-of-materials costs can be kept in check, it simultaneously pushes up the development outlay and can cause time to market delays. It also makes the product vulnerable to risks stemming from lack of component availability (leading to an inability to satisfy customer demand in time, or having to do a redesign if vital components are discontinued).
The gen4 series from 4D Systems means that engineering teams can avoid getting bogged down in the complexities of implementing the display and its supporting electronics, and concentrate their efforts on enriching the UX. Incorporating all the necessary digital and analogue circuitry, these advanced HMI modules are supplied in a wide range of size formats and resolutions, with a choice of touch technologies (resistive or capacitive) and I/Os (I2C, SPI, etc.). The associated Workshop4 IDE allows drag-and-drop construction of the GUI without any coding knowledge being required and permits access to predefined fonts, buttons, sliders, dials and gauges. Finally, the innate modularity of this product offering future-proofs the GUI design, allowing it to be rapidly ported to displays with different resolutions or sizes, should requirements alter.