Human Machine Interface


so subtle, great attention must be paid to noise when designing the controller. Furthermore, the many channels must operate at high frequency in order to win an acceptable ‘frame rate’ from the touch panel. Matching between the channels must be good in order to simplify subsequent processing, calling for tight control over circuit properties and stray capacitances. One popular way of improving the signal-to-noise ratio is to drive the wires at moderately high voltage, maximising the currents being measured. However, this requires specialised components to switch and distribute the excitation, and a dedicated circuit to generate it from whatever low-voltage source is available.


The application of ASICs to these challenges


When such systems are initially prototyped, these electronic functions are provided by a multitude of off-the-shelf integrated circuits (ICs) supported by an array of capacitors and resistors. This is the optimal approach when prototyping, as it provides the opportunity to understand what


specifications are important to the solution. It also gives the developer freedom to experiment with novel hardware approaches to the problem in hand. But to translate a prototype into a cost and performance optimised high-volume product, developers will integrate as much of the circuitry as possible into an ASIC. Swindon frequently designs and supplies custom, high-throughput, multi-channel solutions into human-computer interface applications, optimising the overall bill of materials and achieving form factors that are otherwise impossible. Modern high pin-count packages accommodate many channels in a single part, with excellent matching in properties. Because the cost of replicating identical channels is relatively low, the ASIC approach can be extremely effective in these applications. Furthermore, novel circuits are protected from prying eyes — an ASIC is far more difficult to reverse engineer than discrete parts wired together in plain sight. As Swindon does not develop or sell standard parts on the open market, customers can be confident that their solution and IP benefits them, and them alone.


The ASIC design process itself is heavily based on simulation, incorporating all relevant parasitic capacitance, resistance and inductance so that performance is assured. Noise, being so critical to touch- screen applications, can be accurately predicted and mitigated. The digital processing can also be integrated, either by deployment of processor IP or of custom synthesised logic, and the entire signal path can be optimised as one. By honing the specifications of each element, silicon area and design effort is expended only where absolutely necessary. In contrast, when designing with off-the-shelf ICs, it is inevitable that some aspects will be over-engineered because these components are sold with versatility in mind.


Designing an ASIC


Whilst not always necessary, a working prototype system provides a superb basis for an initial discussion with an ASIC supplier. When customers first engage with Swindon, our priority is to fully understand their concept, allowing us to quickly assess whether a custom solution


might benefit them and if so, to identify the optimum system partitioning. Having established and captured the customer requirements, the chip is then broken down into analogue and digital blocks, each with its own specification. The design of these blocks is distributed across a team of engineers who are accustomed to relying on sophisticated simulation to guide their work. Unlike many other fields of engineering, there are no prototypes when designing integrated circuits: nothing is manufactured or measured until the entire design is finished.


Touch-panels are just one application of ASICs, but they serve to demonstrate the value that integration can bring. The benefits are such that an ASIC sits behind every touch-panel we encounter in our daily lives, although we may not realise it. It is impossible to imagine what technology will eventually displace touch: perhaps mid-air gesture control, or brain-computer interfaces? But no matter what triumphs, it is safe to assume that it too will rely on a custom IC.


https://www.swindonsilicon.com Advertorial


Robust, attractive HMIs – now with vivid LED symbol and halo illumination


I


n response to escalating market demand EAO has enhanced its popular Series 82 family of push-button HMIs with the addition of devices that feature ultra-high contrast red, green, blue, white or red/ green LED illumination. The boosted symbol and halo illumination level provided by the new push-buttons enhances the visibility of standard or custom switch status symbols in most ambient conditions.


The new Series 82 switches are available with silver alloy or gold-plated switching elements in momentary or maintained action variants. The built-in high contrast LEDs provide single and bi-colour illumination.


According to Robert Davies, marketing manager with HMI specialist EAO, many HMI


www.cieonline.co.uk “


applications have to deliver status feedback, so at all times the operator knows precisely the status of the machine under his/her control: “Visual and tactile feedback provides certainty that a machine or device is in passive or operational mode (switched on or off) and assurance that it’s functioning correctly”, Davies said.


Typical Applications n Machinery and factory equipment n Food and beverage manufacture n Access control and security systems


Visual and tactile feedback provides certainty that a machine or device is in passive or operational mode (switched on or off) and assurance that it’s functioning correctly


n Medical equipment n Heavy Duty & Special Vehicles n Road, rail and marine transport control panels


Combined with the modern and stylish design and front-panel presence offered by all Series 82 push-buttons the highly effective symbol illumination delivered by the new metal-bodied, 22mm devices enhances both the visual appeal and functionality of the new


switches in almost any application. “The added benefits of plug-in terminals, IP65/IP67 front protection and a service life of >1million operational cycles render the new Series 82 pushbutton the ideal choice for stylish, vandal-resistant HMI controls in public areas, access control and in harsh industrial environments”, Davies concluded.


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ttp://www.eao.co.uk/ 01444 236 000


Components in Electronics May 2022 33


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