Developing a Touchscreen Wall Terminal

Written by Marko Jankovec on May 21, 2016

We developed an enterprise-grade wall terminal for a well-known international company.

Upgrading an existing terminal

In 2015, we were contacted by a well-established company positioned as the market leader in its field in several countries. Their paramount product, a wall-mountable terminal, has matured and was required to evolve in order to keep up with current trends in their field. Although retaining a stable market position, the terminal with a non-touch monochromatic display and regular buttons most certainly could not compete with younger cousins on the market due to its legacy user interface and, at some point, due to lack of smartphone connectivity.

Because of its legendary status on the market the provider decided to leave its exterior design intact and, instead, only perform a smaller facelift. Luckily, the hardware part of this project is a completely different story...

Facelift outside, rebirth inside

While the enclosure was minimally changed, the role of MULTILUX in this project was to completely redesign the terminal's hardware and develop a new PCB starting from scratch. The previous hardware was based on a classic microcontroller without modern periphery, so we decided to knock it up a notch. This is what we've cooked:

  • the microcontroller was replaced by an ARM Cortex processor running a Linux platform
  • we used a modern LCD touchscreen in order to support smooth user interfaces and applied strengthend cover glass to make sure it wouldn't break so easily (or at all)
  • we redesigned the network interface and improved Power over Ethernet functionality
  • a dual RFID reader was implemented with support for 13.56 MHz and 125 kHz cards
  • a front-facing camera was added to the device in order to enable video communication
  • we added an internal USB port and plugged in a Bluetooth Low Energy (BLE) dongle so that smartphones will be able to communicate to the terminal
  • we added support for a fingerprint reader

Of course, we could have not jumped directly to designing a PCB containing all these candies. According to good engineering practice, we first had to check a few things...

Keeping it cool

Since we wanted to fill the existing enclosure with a brand new PCB, the main question was - will it fit? We are actually very keen on routing four-layer PCBs, so we were quite confident that we could design a small-enough PCB. Nevertheless, having many powerful components in a such small place may result in overheating. Therefore, we first developed a thermal model of the approximate PCB we were going to design within the existing enclosure. Thermal simulations confirmed that the temperature rise would not exceed defined thresholds, so we could have calmly continued designing the PCB.




Engineers love models


We are not talking about that kind of models, though. While developing PCB schematics, the PCB layout was already being designed along. Namely, if we wanted to fit the PCB into the existing enclosure and make it appropriate for high-volume serial production, we had to think about mounting the PCB in the enclosure already in the early design stages. Therefore, we were combining schematic and layout PCB design together with 3D modeling with the aim to construct a product that will be easily produced in high volumes. This was actually a really good idea since it enabled us to foresee possible mounting problems already in the design stage (i.e. in the model) without having to adapt the prototypes once they were produced.

Fitting it all together

When having modeled the PCB, we were not only modeling the circuit part but the whole product. We started by importing the existing enclosure's model and merged it with our PCB model. Then, we added the LCD and some auxiliary parts together with screws. We of course made a few iterations in order to find an optimal way of mounting.

Reporting to our partner

In order to keep track of the project, we were regularly reporting to our partner who was in the role of the client. At MULTILUX, we use JIRA to manage all our projects. Using JIRA, we allow our partners watch the project's progress in real time as we give them access to participate in project management. Our partners can, therefore, monitor the project's progress by supervising task resolution and can even contribute comments.


Of course, software tools cannot replace human interaction which is why we held regular meetings with our partner in order to comment on possible issues and their resolution. This proved to be a very efficient way of handling issue resolution since we could have discussed them in person and together agree on the project's course of action.

Precompliance testing

MULTILUX specializes in achieving compliance with valid standards and directives already in early design stages. Besides doing development in accordance with good engineering practice, we also provide measurements of electromagnetic compatibility (EMC) and radiofrequency spectre (RF) in order to better predict what results to expect from compliance test in the certified lab.

When we produced the prototypes for the touchscreen wall terminal, we tested them for electromagnetic compatibility and both conductive and radiated emissions. We performed tests by both placing the device in a TEM cell and compare measurements to valid standards' boundaries, and by using an EMC scanner that can accurately show possible disruptions by mapping them to an exact location on the PCB.

Finetuning

Since the developed touchscreen wall terminal is a high-end device with complex electronics, there are many onboard components that may emit in the RF spectre and lead to failed compliance tests. The PCB we developed passed all RF & EMC tests in the certified lab, yet we had to further improve it to be more robust and pass the electrostatic discharge (ESD) test. It is quite common for EMC-friendly hardware to fail on ESD tests.

After a thorough investigation of our top engineer, we determined that there were some minor issues with onboard components. That meant we had to finetune the PCB and determine what exact component was causing trouble. We applied some patches which led to improved robustness and stability, allowing us to finally pass all compliance tests in the certified lab.

By having successfully certified this high-end device that we had developed from scratch, we therefore confirmed that our good engineering practice is indeed good, and MULTILUX' small yet experienced team can successfully handle complex projects from idea to the final product.



At MULTILUX, we are very satisifed with final results and, also, that we could have taken part in this project that enabled us to demonstrate how we can handle enterprise-grade product development and assure compliance with standards as our products pass compliance tests in the certified lab. Of course, our partner was satisfied as well.

Does your project require a full-stack engineering team?

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