Page 38

EETE JUN 2015

DISPLAYS & interfaces Exploring new dimensions for HMI technology TBy Gordon Lunn ouch-enabled human machine interfaces (HMIs) offer a more intuitive and natural means by which to operate electronics hardware than traditional electromechanical switches and pushbuttons, thereby delivering more enjoyable user experiences. They are now employed almost universally in consumer electronics products and new opportunities are emerging all the time for their inclusion inside a broad spectrum of other system designs - including retail, medical, home automation, industrial control and white goods. Though generally the HMIs for portable consumer products can be considered as simply standalone in nature, there are a great many situations elsewhere that are in need of multiple units being interfaced together to create a more comprehensive system. This article will look at some examples of applications in which this sort of HMI structure is warranted. There are a plethora of potential everyday scenarios that will see major benefits from the coupling together of HMIs, in such a way that there is a consistency between what is displayed on each. Through this the data being input at one HMI will be easy to comprehend by whoever is operating/viewing another HMI to which it has been connected. Arrangements are likely to vary - in certain cases these HMIs will be have a peer-to-peer topology, while in others there will be multiple units all connected to one another through a central server. For instance, in the retail sector, shoppers would be able to select the merchandise they want to buy from a store utilising a point-of sale unit. This information could then be fed back to the warehouse so that these items could be made ready for collection. Likewise, in a restaurant touch panels could be embedded into each of the tables. Through these the customers could choose the food and beverages they would like to order and this data would subsequently be transferred to the corresponding display located in the kitchen. In home automation, it could also be of value, allowing the occupant to the set temperature in one room with the information being made available on each of the display units within the network. So, given that there are already a multitude of possible opportunities for assemblies of this kind, why hasn’t this really been done before? The answer, at least partially, lies in the fact that the HMI systems currently in place are often too complex and costly to make it economically and operationally viable. However, things are changing - recent developments in the supporting semiconductor technology could have major implications on how engineers think about HMI construction in the future. The changing face of HMI implementation HMI systems will normally have a structure similar to the one described in Figure 1. Here a high performance (16-bit or 32-bit) microcontroller unit is responsible for creating and manipulating of the graphics that are rendered on the display. Alongside it there is a sizeable non-volatile memory resource Fig. 1: Conventional System for a Touch-Enabled HMI. in which all of these graphics are stored, plus a capacious frame buffer which is needed for graphics processing purposes and a series of wide data buses for carrying out communication between these devices. On top of all this, a touch controller and an audio DAC converter must be specified to take care of the touch inputs being registered and the sound output respectively. The number of different chips involved results in a substantial bill of materials being associated with this sort of system design. Furthermore, as each of these chips has quite a high pin count, the board space that such a system takes up can also be an issue. The system’s complexity means that a lot of engineering effort is required to implement it, and the relatively large power consumption is also a factor. Figure 2 details an alternative solution which is far more streamlined than the conventional approach to HMI implementation. It greatly reduces the number of components needed and the amount of data that must be transferred between them. The board real estate that must be allocated is much lower, as is the engineering overhead relating to its development. This solution is based on FTDI Chip’s EVE (Embedded Video Engine) technology. As EVE devices incorporate display, audio and touch functionality into a single chip (thanks to the built-in touch controller and single channel audio controller) there are immediate benefits in terms of board space and system complexity - but in addition to the EVE concept tackles HMI deployment in a whole different way to the conventional approach already discussed. Here all of the graphic and audio elements that make up the HMI design are treated as objects. These objects - bitmap images, fonts, chirps, beeps, templates, overlays, logos, and suchlike, are effectively denoted in a ‘shorthand’ form. Gordon Lunn is global customer engineer support manager at FTDI Chip - www.ftdichip.com Fig. 2: Rationalised HMI System Using EVE Technology. 30 Electronic Engineering Times Europe June 2015 www.electronics-eetimes.com


EETE JUN 2015
To see the actual publication please follow the link above