Using Small PCs in New Ways

Innovative Interfacing

Even simple MCU-based projects often require some sort of front panel interface. Traditionally such systems had to rely on LEDs and switches for such simple interfaces. These days however, you can buy small, inexpensive computing devices such as mini PCs and tablet computers and adapt them to fill those interfacing roles. In this article, Wolfgang steps you through the options and issues involved in connecting such PC-based devices to an MCU-based environment.

By Wolfgang Matthes

More often than not, even a humble project—done for educational, tinkering or just for fun—needs some way to display something and to allow for operator interaction. That means contemplating how best to craft an operator console, a control panel, a display assembly or how to set up a testbed and the like. Solderless breadboards, jumper wire and the ubiquitous small modules were the traditional tools for such efforts—in the past there was no other way than to build real hardware from scratch.

It goes without saying that today’s state-of-the-art technology is characterized by computers with touchscreens and the like. Simply run your favorite flight simulator and compare the cockpits of an old Super Constellation or F-86 aircraft to the cockpits of a Boeing 777 or an F-22. In down-to- earth projects, it is quite natural to think of industrial-grade hardware—industrial PCs, embedded PCs and so on. But those can be way too expensive for our low-budget projects. That’s why we think about using small, inexpensive personal computers (PCs). This topic is best clarified through photos. With that in mind, besides what’s in this article, more photos can be found on Circuit Cellar’s article materials webpage.

Figure 1
Shown here are some jerry-built display and control panels

Figure 1 shows some devices that are essentially basic display and control panels. In most educational, tinkering or fun projects, it’s not practical to spend a lot of time and money to design and build impressive assemblies and panels. More often than not, the problem is solved by more or less sloppy tinkering. In contrast, the devices shown here are somewhat more advanced. They are still jerry-built, but they are crafted with sturdiness as a main objective.

Figure 2
Each of these basic control panels support eight digital outputs operated via toggle switches, and eight inputs whose levels are indicated by LEDs or on an LCD display.

Figure 2 shows three boxes that are basic control panels, each supporting eight inputs and eight outputs. While the device to the left is clearly jerry-built, the two other devices are the result of meticulous mechanical design—they were conducted as experiments (and student assignments) with an intentional disregard of cost. Figure 3 shows the interior of the most sophisticated of the control panels. It supports signal levels between 2.5 V and 24 V, remote operation via the USB and an LCD display. Under program control, it can be operated as a small quasi-static digital tester. When you need more than eight inputs or outputs, attach two or more panels via a USB or serial hub.

Figure 3
The interior of the somewhat more advanced (and expensive) control panel—the result of an exercise in mechanical and PCB design. The ribbon cables connect only the pin headers in the front panel. The PCBs are stacked one above the other, thereby avoiding cables or wiring harnesses.

It goes without saying that such a device is not that cheap. The bill-of-materials (BOM) cost alone could pay for more than one small tablet PC running Windows. Figure 4 shows an 8″ tablet in a purpose-built frame, attached to a test rig and two 7″ tablets in a 19″, 3U subrack. In contrast, those devices are considerably less expensive than the apparatus shown in Figure 3.

Figure 4
These are examples of small Windows tablets adapted to serve as operator consoles, diagnostic displays and testbed controllers.

Employing a PC requires programming skills, but no special craftsmanship or a workshop full of tools. Yes, writing and debugging programs may be challenging. But it’s a lot more forgiving than a mechanical interface where you could accidently turn a front panel into scrap metal, simply due to a misplaced hole or dealing with mismatched connections that only show up when you’re fitting the parts together. …

Read the full article in the September 350 issue of Circuit Cellar
(Full article word count: 4678 words; Figure count: 18 Figures. plus supplemental Figures here.)

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September Circuit Cellar: Sneak Preview

The September issue of Circuit Cellar magazine is out next week! This 84-page publication stitches together a fine tapestry of fascinating embedded electronics articles crafted for your reading pleasure.

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TECHNOLOGY FOR SECURITY, SENSORS & THE IoT

Security Solutions for IoT
By Jeff Child
In this IoT era of connected devices, microcontrollers have begun taking on new roles and gaining new capabilities revolving around embedded security. MCUs are embedding ever-more sophisticated security features into their devices-both on their own and via partnerships with security specialists. Here, Circuit Cellar’s Editor-in-Chief, Jeff Child, looks at the latest technology and trends in MCU security.

Electromagnetic Fault Injection: A Closer Look
By Colin O’Flynn
Electromagnetic Fault Injection (EMFI) is a powerful method of inserting faults into embedded devices, but what does this give us? In this article, Colin dives into a little more detail of what sort of effects EMFI has on real devices, and expands upon a few previous articles to demonstrate some attacks on new devices.
 
Product Focus: IoT Gateways
By Jeff Child
IoT gateways are a smart choice to facilitate bidirectional communication between IoT field devices and the cloud. Gateways also provide local processing and storage capabilities for offline services as well as near real-time management and control of edge devices. This Product Focus section updates readers on these technology trends and provides a product gallery of representative IoT gateways.
 
Comparing Color Sensor ICs
By Kevin Jensen
Driven by demands from mobile phone, display and specialty lighting equipment manufacturers, the need for sophisticated and accurate chip-scale color and spectral sensors has become stronger than ever. In this article, ams’ Kevin Jensen describes the types of optical sensors and detectors. He also provides ideas on evaluating the suitability of each type for specific applications.

PC-BASED SOLUTIONS FOR EMBEDDED SYSTEMS
 
Mini-ITX, Pico-ITX and Nano-ITX Boards
By Jeff Child
Products based on the various small-sized versions of the ITX form factor—Mini-ITX, Pico-ITX and Nano—ITX-provide system developers with complete PC-functionality and advanced graphics. Circuit Cellar Chief Editor Jeff Child explores the latest technology trends and product developments in these three ITX architectures.
 
Using Small PCs in New Ways
By Wolfgang Matthes
Even simple MCU-based projects often require some sort of front panel interface. Traditionally such systems had to rely on LEDs and switches for such simple interfaces. These days however, you can buy small, inexpensive computing devices such as mini-PCs and notebook computers and adapt them to fill those interfacing roles. In this article, Wolfgang steps you through the options and issues involved in connecting such PC-based devices to an MCU-based environment.



FOCUS ON MICROCONTROLLERS
 
Guitar Game Uses PIC32 MCU
By Brian Dempsey, Katarina Martucci and Liam Patterson
Guitar Hero has been an extremely popular game for decades. Many college kids today who played it when they were kids still enjoy playing it today. These three Cornell students are just such fans. Learn how they used Microchip’s microcontroller and 12-bit DAC to craft their own version that lets them play any song they wish by using MIDI files.
 
Offloading Intelligence
By Jeff Bachiochi
While some embedded systems do just fine with a single microcontroller, there are situations when offloading some processing into a second processing unit, such as a second MCU, offers a lot of advantages. In this article, Jeff explores this question in the context of a robotic system project that uses Arduino and an external motor driver.
 
Building a Portable Game Console
By Juan Joel Albrecht and Leandro Dorta Duque
32-bit MCUs can do so much these days—even providing all the needed control functionality for a gaming console. Along just those lines, learn how these three Cornell students built a portable game console that combines a Microchip PIC32 MCU embedded in a custom-designed 3D-printed case, printed circuit board and in-house gameplay graphics. The device includes a 320 x 240 TFT color display.
 


… AND MORE FROM OUR EXPERT COLUMNISTS
 
Variable Frequency Drive Part 2
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In Part 1 Brian started to describe the process he used to convert a 3-phase motor and OEM Variable Frequency Drive (VFD) controller—salvaged from his defunct clothes washer—into a variable speed drive for his bandsaw. In this article, he completes the discussion this tim,e covering the Cypress Semi PSoC5LP SoC he used, the software design and more.
 
Semiconductor Fundamentals Part 1
By George Novacek
Embedded systems—or even modern electronics in general—couldn’t exist without semiconductor technology. In this new article series, George delves into the fundamentals of semiconductors. In Part 1 George examines the math, chemistry and materials science that are fundamental to semiconductors with a look at the basic structures that make them work.