# Accelerometers Revisited

MEMS and More

In his March article, George reviewed the major aspects of acceleration, along with its measurement and the design fundamentals of the sensors known as accelerometers. Here, he expands on the topic exploring the electronics portion of accelerometers along with a look at how MEMS technology plays a role in these sensors.

By George Novacek

The key aspects of accelerometers can be loosely categorized by their acceleration range, frequency response and typical applications as shown in Table 1. Many characteristics must be taken into account when selecting an accelerometer suitable for the given task. Besides having to satisfy the required range of acceleration to be measured, you must consider the measurement resolution, accuracy, bandwidth, stability and repeatability. Just as important are the weight, size, cost, electrical interfaces, power consumption, availability and operating environmental conditions. And don’t forget susceptibility to the effects of conducted and radiated emissions, that is electromagnetic interference (EMI).

Fundamentally, accelerometers are electromechanical devices—as I have shown in my March 2018 article (Circuit Cellar 332). Electronics play only a supporting role—needed to convert the displacement of the proof (also called seismic) mass into a useful electrical signal. Accelerometer interfaces can take many forms, both analog and digital.

Figure 1
The mechanical principle of an accelerometer

The behavior of the mechanical system illustrated in Figure 1 is described by just a few simple equations, where the variables are the force F = kx developed by the spring, the opposite force F = Dv developed by the damper and the seismic mass’ inertial force F = Ma. Consequently, the static displacement of the mass equals to:

The combination of the spring, the damper and the mass form a second-order system. Such a system, when exposed to varied acceleration of angular frequency ω which equals to 2πf, exhibits dynamic behavior described by equation:

The resonant frequency of this system will be:

and the quality factor:

The frequency response of such a system was shown in the March issue. The parameter ξ is the system damping factor.

MEMS and Acceleration

At present, the most popular manufacturing technology for accelerometers as well as many other inertia-based sensors—such as gyroscopes—is MEMS. MEMS is an acronym for “micro electro-mechanical system.” MEMS accelerometers measure the proof mass displacement by piezoresistive or capacitive sensors.  …

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# Online Course Covers IoT-Enabled Embedded Systems

STMicroelectronics has announced the availability to all–including students, makers, and budding engineers and computer scientists–of the online “Introduction to Embedded Systems with SensorTile” course. With a curriculum developed by Professor William Kaiser at the University of California, Los Angeles (UCLA), and used to teach his freshman engineering class, the online course resources provide a foundation to understand the fundamentals of a sensor-based Internet of Things (IoT)-enabled embedded system. Professors at other universities are also encouraged to adapt and contribute to the course.

The introductory course of 8 self-paced tutorials is designed around ST’s SensorTile, a unique real-time IoT-enabled embedded system on a postage-stamp-sized module. The tiny 13.5 mm x 13.5 mm module combines a high-performance, low-power STM32 Arm-Cortex-M-core microcontroller, 5 valuable MEMS (Micro-Electro-Mechanical Systems) sensors—an inertial sensor containing an accelerometer and gyroscope, an eCompass, a pressure sensor, and a microphone—and a Bluetooth network processor. A kit with the module, cables, cradle and a battery is available from major resellers for about \$80.

The joint effort with ST makes the 8 tutorials freely available online, with a full complement of documentation, open-source algorithms and development solutions, and unfettered access to a growing user forum. Anyone interested in learning more about the tutorial or purchasing a SensorTile kit should visit the web site www.st.com/sensortile-edu). Additional information is available, as well, on the ST blog: blog.st.com/introduction-embedded-systems-sensortile-online-course/

STMicroelectronics | www.st.com

# BLE Module Boasts Integrated MEMS Sensors

Telit has announced BlueMod+S42M, a Bluetooth Low Energy (BLE) 4.2, standalone, single-mode module with embedded 3-axis accelerometer, temperature and humidity sensors. The cost-effective component is optimized for efficiency and simplicity in end-device design and manufacturing, delivering reliable Bluetooth Low Energy functionality with robust endpoint security, motion and environmental sensors and essential features that reduce development costs, bill of materials, and time to market.

Ideal for large scale projects, the BlueMod+S42M seamlessly expedites device design across a wide range of industrial and consumer applications areas. The embedded sensors are necessary for high-value, fragile asset tracking, and time- or temperature-sensitive applications such as cold chain monitoring in the pharmaceutical and agriculture industries.

Telit | www.telit.com

# Cypress Announces Highly-Integrated Programmable EZ-PD CCG3PA USB-C Controller with Power Delivery 3.0 and Quick Charge 4.0 Support

During Computex 2017, Cypress Semiconductor announced availability of a new USB-C controller with Power Delivery (PD) that streamlines the design of power adapters, chargers, and power banks. The EZ-PD CCG3PA controller supports the PD 3.0 standard with programmable power supply (PPS) and Qualcomm’s Quick Charge (QC) 4.0 protocol, which enable new power source product designs to provide an improved fast charging user experience.

As these standards and the USB Type-C standard continue to evolve, compliance and interoperability pose an ongoing challenge, but the programmable CCG3PA controller enables firmware upgradeability to keep up with changes and overcome interoperability issues. The new Cypress controller offers a high level of integration that minimizes bill-of-material costs and simplifies designs, replacing multiple discrete components with a single-chip solution.

“As USB-C proliferates this year, the demand for USB-C power sources will increase, putting more pressure on our customers to bring their power adapters, mobile chargers, car chargers and power banks to market quickly, while keeping up with rapidly evolving USB standards,” says Ajay Srikrishna, vice president of Cypress’ Wired Connectivity Business Unit. “Our highly-integrated EZ-PD CCG3PA controller is optimized to simplify the design of USB-C power source products, with support for the required charging standards, and the ability to upgrade firmware to keep pace with changes in standards.”

The EZ-PD CCG3PA controller is a one-chip solution that minimizes bill-of-material costs for USB-C power source products by integrating error amplifiers for constant voltage, constant current and PPS applications, a 30 V regulator that allows direct operation from VBUS, VBUS short protection on configuration channel (CC) pins, gate drivers for high-voltage power FETs, a low side current sense amplifier, and dedicated hardware for legacy charger detection protocols plus system level electrostatic discharge (ESD) protection.

Programmable overvoltage and overcurrent circuitry protects systems against power overloads and other faulty operating conditions. The controller also integrates an ARM Cortex-M0 and 64KB Flash with read-while-write function for firmware upgradeability. The product enables design of efficient USB-C power adapters for a wide range of applications.

The EZ-PD CCG3PA controller is now sampling in 24-pin QFN (16 mm2) and 16-pin SOIC (60 mm2) packages. The controller will be in production in the third quarter of 2017. Designers can get started with the CY4532 CCG3PA evaluation kit (pictured below), which is now available for \$149. Cypress provides CCG3PA solution reference designs for a 45-Watt notebook PC power adapter, a 27-Watt mobile phone charger, a 60-Watt car charger and a power bank. More info on Cypress’ USB Type-C and PD solutions is available at www.cypress.com/Type-C.

Cypress’ EZ-PD portfolio of USB-C controllers already includes the CCG1, CCG2, and CCG3 programmable USB-C controllers, the CCG4 two-port USB-C solution, and CCG5, the market’s first two-port USB-C solution optimized for Thunderbolt notebook and desktop PCs, all supporting the latest USB PD 3.0 specification.

The USB Type-C standard is gaining rapid support with top-tier electronics manufacturers by enabling slim industrial designs, easy-to-use connectors and cables, and the ability to transmit multiple protocols and deliver up to 100 Watts of power.

# Vesper VM1010 MEMS Microphones

Vesper recently launched the VM1010, which is the first wake-on-sound MEMS microphone that consumes nearly zero power. It allows consumers to voice-activate battery-powered smart speakers, smart earbuds and TV remotes without draining the battery. The inaugural member of Vesper’s ZeroPower Listening MEMS microphone product line, the VM1010 is a tiny, ultra-rugged piezoelectric MEMS microphone that that enables you to offer touchless user interfaces to consumers without any power-consumption penalty.

Consuming a mere 6 µA while in listening mode, the Vesper’s VM1010 extends battery life to months or years by enabling the rest of the system to completely power down while waiting for a keyword. That is a major advantage to designers who can create an entirely new class of rugged, battery-operated, voice-interface devices that work anywhere.

The VM1010 is a low-noise, high dynamic range, single-ended analog output piezoelectric MEMS microphone. It features a configurable voice zone, allowing voice in a 5-foot radius to 20-foot radius-zone to trigger the system and increase to a normal operation mode. When the environment is quiet, the system can enter ZeroPower Listening mode and the entire system can power down.

Like other Vesper piezoelectric MEMS microphones, the VM1010 sets the standard for reliability and stability, even in harsh environments. It is dustproof to IP5X and waterproof to IPX7. Because it is stable in all environments, the VM1010 microphones are also ideally suited to microphone arrays, which are critical to far-field audio applications. Drawing a mere 6 µA of power in always-listening mode, the VM1010 extends battery life 10× or more.

Vesper’s VM1010 is currently sampling and is available online through Digi-Key. Test boards and reference design boards using VM1010, DSP Group’s DSPG DBMD6 and Sensory’s Truly Handsfree wake word algorithms are available from Vesper via an exclusive invitation-only program.

Vesper’s MEMS microphones represent a radical shift from the capacitive MEMS microphones that are shipping by the hundreds of millions in smartphones, hearables, smart speakers, Internet of Things devices and connected cars. Vesper’s piezoelectric design is waterproof, dustproof, particle-resistant and shockproof. Piezoelectric MEMS microphones make voice-interface devices practical in any environment, and they are also ideally suited for far-field applications such as microphone arrays.

Source: Vesper

# New MEMS Accelerometers for Industrial Condition Monitoring Apps

Analog Devices’s new ADXL1001 and ADXL1002 high-frequency, low-noise MEMS accelerometers are designed for industrial condition-monitoring applications. The accelerometers deliver the high-resolution vibration measurements needed for the early detection of machine failure (e.g., bearing faults).

• Deliver ultra-low noise density over an extended bandwidth with high-g range.
• Available in two models with full-scale ranges of ±100 g (ADXL1001) and ±50 g (ADXL1002).
• Typical noise density for the ADXL1002 is 25 μg/√Hz, with a sensitivity of 40 mV/g, and 30 μg/√Hz for ADXL1001 with sensitivity 20 mV/g.
• Operate on single voltage supply from 3. to 5.25 V
• Electrostatic self-test
• Over range indicator
• Rated for operation over a –40°C to 125°C temperature range.

The accelerometers cost \$29.61 each in 1,000-unit quantities.

Source: Analog Devices

# STMicroelectronics To Manufacture USound’s Patented Thin-Film Piezo-Electric MEMS Micro-Speaker Technology

STMicroelectronics and Austrian company USound GmbH announced their collaboration on the industrialization and production of the world’s first miniature piezoelectric MEMS actuators for smart audio systems in portable devices. The patented micro-speaker technology from USound aims to replace commonly used balanced-armature and electrodynamic receivers for handsets with a small piezo-MEMS actuator.

Manufactured using STMicroelectronics’s industry-leading thin-film piezoelectric (TFP) technology, these actuators will improve scalability and cost while assuring lower power consumption and heat dissipation in hearables and smartphones devices, without compromising audio quality.

USound and STMicroelectronics anticipate the piezoelectric MEMS actuator will move into production in Q3 of this year and will be shipping in consumer products by the end of the year.

Source: STMicroelectronics

# Scalable Wearable Development Kit

ON Semiconductor recently announced the availability of a new Wearable Development Kit (WDK1.0). The kit comprises the following: a touchscreen display; wired and AirFuel-compatible wireless charging capability; a six-axis motion sensor and temperature sensor; an alarm, timer, and stopwatch; schematics; firmware and sample code; a dock station for charging; and a downloadable SmartApp for evaluating and controlling the smartwatches multiple functions.

The WDK1.0’s features, specs, and benefits:

• NCP6915 power Management IC provides five LDOs and one DC-DC
• NCP1855 battery charger IC, an LC709203F fuel gauge, and a 10-W rated SCY1751 wireless charging front-end controller
• MEMS-based FIS1100 IMU, with three‐axis gyroscope and three‐axis accelerometer operation for multidimensional motion tracking
• Embedded temperature sensor included and an LC898301 driver IC for initiating haptic feedback
• nRF52832 multi-protocol system-on-chip (SoC)
• Eclipse-based IDE
• 1.44″ 128 × 128 pixel TFT display with a capacitive touch screen
• 26‐pin expansion port

Source: ON Semiconductor

# New Low-Cost MEMS Inertial Accelerometer

Silicon Designs recently announced the North American market introduction of the new Model 1525 Series integral inertial accelerometer family. Offering impressive low-noise performance, the nitrogen damped and hermetically sealed SDI Model 1525 Series is intended for tactical navigation, seismic, and other zero-to-medium frequency instrumentation applications that require high-repeatability, low noise, and maximum stability.

Each miniature, hermetically sealed package combines a MEMS variable capacitive sense element and a custom integrated circuit that includes both a sense amplifier and 4.0 V differential output stage. Units are available in six unique full-scale ranges from 2 g to 100 g with reliable performance over a standard operating temperature range of –40°C to 85°C. Each device has a serial number for traceability. Each unit comes with a calibration test sheet showing measured bias, scale factor, linearity, operating current, and frequency response.

Source: Silicon Designs

# STMicro Reduces Time to Development with Open.MEMS Licensing

STMicroelectronics recently announced the launch of the Open.MEMS licensing program. Its purpose is to encourage broad use of its MEMS and sensors among open-community developers. Open.MEMS licensees can access free drivers, middleware, and application software, beginning with “sensor fusion for 3-axis accelerometer, 3-axis gyroscope, and 3-axis magnetometer, considered vital for many portable and wearable applications.”

STMicro’s STM32 Open Development platform supports Open.MEMS, which went live on November 11, 2014, and will continue to be expanded regularly with additional low-level drivers, middleware/libraries, and application-layer code.

# Q&A: Embedded Systems Consultant

Elecia White is an embedded systems engineer, consultant, author, and innovator. She has worked on a variety of projects: DNA scanners, health-care monitors, learning toys, and fingerprint recognition.—Nan Price, Associate Editor

NAN: Tell us about your company Logical Elegance. When and why did you start the company? What types of services do you provide?

ELECIA: Logical Elegance is a small San Jose, CA-based consulting firm specializing in embedded systems. We do system analysis, architecture, and software implementation for a variety of devices.

Elecia White

I started the company in 2004, after leaving a job I liked for a job that turned out to be horrible. Afterward, I wasn’t ready to commit to another full-time job; I wanted to dip my toe in before becoming permanent again.

I did eventually take another full-time job at ShotSpotter, where I made a gunshot location system. Logical Elegance continued when my husband, Chris, took it over. After ShotSpotter, I returned to join him. While we have incorporated and may take on a summer intern, for the most part Logical Elegance is only my husband and me.

I like consulting, it lets me balance my life better with my career. It also gives me time to work on my own projects: writing a book and articles, playing with new devices, learning new technologies. On the other hand, I could not have started consulting without spending some time at traditional companies. Almost all of our work comes from people we’ve worked with in the past, either people we met at companies where we worked full time or people who worked for past clients.

Here is Elecia’s home lab bench. She conveniently provided notes.

NAN: Logical Elegance has a diverse portfolio. Your clients have ranged from Cisco Systems to LeapFrog Enterprises. Tell us about some of your more interesting projects.

ELECIA: We are incredibly fortunate that embedded systems are diverse, yet based on similar bedrock. Once you can work with control loops and signal processing, the applications are endless. Understanding methodologies for concepts such as state machines, interrupts, circular buffers, and working with peripherals allows us to put the building blocks together a different way to suit a particular product’s need.

For example, for a while there, it seemed like some of my early work learning how to optimize systems to make big algorithms work on little processors would fall to the depths of unnecessary knowledge. Processors kept getting more and more powerful. However, as I work on wearables, with their need to optimize cycles to extend their battery life, it all is relevant again.

We’ve had many interesting projects. Chris is an expert in optical coherence tomography (OCT). Imagine a camera that can go on the end of a catheter to help a doctor remove plaque from a clogged artery or to aid in eye surgery. Chris is also the networking expert. He works on networking protocols such as Locator/ID Separation Protocol (LISP) and multicast.

I’m currently working for a tiny company that hopes to build an exoskeleton to help stroke patients relearn how to walk. I am incredibly enthusiastic about both the application and the technology.

That has been a theme in my career, which is how I’ve got this list of awesome things I’ve worked on: DNA scanners, race cars and airplanes, children’s toys, and a gunshot location system. The things I leave off the list are more difficult to describe but no less interesting to have worked on: a chemical database that used hydrophobicity to model uptake rates, a medical device for the operating room and ICU, and methods for deterring fraud using fingerprint recognition on a credit card.

Elecia says one of the great things about the explosion of boards and kits available is being able to quickly build a system. However, she explains, once the components work together, it is time to spin a board. (This system may be past that point.)

In the last few years, Chris and I have both worked for Fitbit on different projects. If you have a One pedometer, you have some of my bits in your pocket.

The feeling of people using my code is wonderful. I get a big kick seeing my products on store shelves. I enjoyed working with Fitbit. When I started, it was a small company expanding its market; definitely the underdog. Now it is a success story for the entire microelectromechanical systems (MEMS) industry.

Not everything is rosy all the time though. For one start-up, the algorithms were neat, the people were great, and the technology was a little clunky but still interesting. However, the client failed and didn’t pay me (and a bunch of other people).

When I started consulting, I asked a more experienced friend about the most important part. I expected to hear that I’d have to make myself more extroverted, that I’d have to be able to find more contracts and do marketing, and that I’d be involved in the drudgery of accounting. The answer I got was the truth: the most important part of consulting is accounts receivable. Working for myself—especially with small companies—is great fun, but there is a risk.

NAN: How did you get from “Point A” to Logical Elegance?

ELECIA: ”Point A” was Harvey Mudd College in Claremont, CA. While there, I worked as a UNIX system administrator, then later worked with a chemistry professor on his computational software. After graduation, I went to Hewlett Packard (HP), doing standard software, then a little management. I was lured to another division to do embedded software (though we called it firmware).

Next, a start-up let me learn how to be a tech lead and architect in the standard start-up sink-or-swim methodology. A mid-size company gave me exposure to consumer products and a taste for seeing my devices on retailer’s shelves.

From there, I tried out consulting, learned to run a small business, and wrote a Circuit Cellar Ink article “Open Source Code Guide” (Issue 175, 2005). I joined another tiny start-up where I did embedded software, architecture, management, and even directorship before burning out. Now, I’m happy to be an embedded software consultant, author, and podcast host.

NAN: You wrote Making Embedded Systems: Design Patterns for Great Software (O’Reilly Media, 2011). What can readers expect to learn from the book?

ELECIA: While having some industry experience in hardware or software will make my book easier to understand, it is also suitable for a computer science or electrical engineering college student.

It is a technical book for software engineers who want to get closer to the hardware or electrical engineers who want to write good software. It covers many types of embedded information: hardware, software design patterns, interview questions, and a lot of real-world wisdom about shipping products.

Making Embedded Systems is intended for engineers who are in transition: the hardware engineer who ends up writing software or the software engineer who suddenly needs to understand how the embedded world is different from pure software.

Unfortunately, most college degrees are either computer science or electrical engineering. Neither truly prepares for the half-and-half world of an embedded software engineer. Computer science teaches algorithms and software design methodology. Electrical engineering misses both of those topics but provides a practical tool kit for doing low-level development on small processors. Whichever collegiate (or early career) path, an embedded software engineer needs to have familiarity with both.

I did a non-traditional major that was a combination of computer science and engineering systems. I was prepared for all sorts of math (e.g., control systems and signal processing) and plenty of programming. All in all, I learned about half of the skills I needed to do firmware. I was never quite sure what was correct and what I was making up as I went along.

As a manager, I found most everyone was in the same boat: solid foundations on one side and shaky stilts on the other. The goal of the book is to take whichever foundation you have and cantilever a good groundwork to the other half. It shouldn’t be 100% new information. In addition to the information presented, I’m hoping most people walk away with more confidence about what they know (and what they don’t know).

Elecia was a judge at the MEMS Elevator Pitch Session at the 2013 MEMS Executive Congress in Napa, CA.

NAN: How long have you been designing embedded systems? When did you become interested?

ELECIA: I was a software engineer at the NetServer division at HP. I kept doing lower-level software, drivers mostly, but for big OSes: WinNT, OS/2, Novell NetWare, and SCO UNIX (a list that dates my time there).

HP kept trying to put me in management but I wasn’t ready for that path, so I went to HP Labs’s newly spun-out HP BioScience to make DNA scanners, figuring the application would be more interesting. I had no idea.

I lit a board on fire on my very first day as an embedded software engineer. Soon after, a motor moved because my code told it to. I was hooked. That edge of software, where the software touches the physical, captured my imagination and I’ve never looked back.

NAN: Tell us about the first embedded system you designed. Where were you at the time? What did you learn from the project?

ELECIA: Wow, this one is hard. The first embedded system I designed depends on your definition of “designed.” Going from designing subsystems to the whole system to the whole product was a very gradual shift, coinciding with going to smaller and smaller companies until suddenly I was part of the team not only choosing processors but choosing users as well.

After I left the cushy world of HP Labs with a team of firmware engineers, several electrical engineers, and a large team of software engineers who were willing to help design and debug, I went to a start-up with fewer than 50 people. There was no electrical engineer (except for the EE who followed from HP). There was a brilliant algorithms guy but his software skills were more MATLAB-based than embedded C. I was the only software/firmware engineer. This was the sort of company that didn’t have source version control (until after my first day). It was terrifying being on my own and working without a net.

I recently did a podcast about how to deal with code problems that feel insurmountable. While the examples were all from recent work, the memories of how to push through when there is no one else who can help came from this job.

Elecia is shown recording a Making Embedded Systems episode with the founders of electronics educational start-up Light Up. From left to right: Elecia’s husband and producer Christopher White, host Elecia White, and guests Josh Chan and Tarun Pondicherry.

NAN: Are you currently working on or planning any projects?

ELECIA: I have a few personal projects I’m working on: a T-shirt that monitors my posture and a stuffed animal that sends me a “check on Lois” text if an elderly neighbor doesn’t pat it every day. These don’t get nearly enough of my attention these days as I’ve been very focused on my podcast: Making Embedded Systems on iTunes, Instacast, Stitcher, or direct from http://embedded.fm.

The podcast started as a way to learn something new. I was going to do a half-dozen shows so I could understand how recording worked. It was a replacement for my normal community center classes on stained glass, soldering, clay, hula hooping, laser cutting, woodshop, bookbinding, and so forth.

However, we’re way beyond six shows and I find I quite enjoy it. I like engineering and building things. I want other people to come and play in this lovely sandbox. I do the show because people continue to share their passion, enthusiasm, amusement, happiness, spark of ingenuity, whatever it is, with me.

To sum up why I do a podcast, in order of importance: to talk to people who love their jobs, to share my passion for engineering, to promote the visibility of women in engineering, and to advertise for Logical Elegance (this reason is just in case our accountant reads this since we keep writing off expenses).

NAN: What are your go-to embedded platforms? Do you have favorites, or do you use a variety of different products?

ELECIA: I suppose I do have favorites but I have a lot of favorites. At any given time, my current favorite is the one that is sitting on my desk. (Hint!)

I love Arduino although I don’t use it much except to get other people excited. I appreciate that at the heart of this beginner’s board (and development system) is a wonderful, useful processor that I’m happy to work on.

I like having a few Arduino boards around, figuring that I can always get rid of the bootloader and use the Atmel ATmega328 on its own. In the meantime, I can give them to people who have an idea they want to try out.

For beginners, I think mbed’s boards are the next step after Arduino. I like them but they still have training wheels: nice, whizzy training wheels but still training wheels. I have a few of those around for when friends’ projects grow out of Arduinos. While I’ve used them for my own projects, their price precludes the small-scale production I usually want to do.

Professionally, I spend a lot of time with Cortex-M3s, especially those from STMicroelectronics and NXP Semiconductors. They seem ubiquitous right now. These are processors that are definitely big enough to run an RTOS but small enough that you don’t have to. I keep hearing that Cortex-M0s are coming but the price-to-performance-to-power ratio means my clients keep going to the M3s.

Finally, I suppose I’ll always have a soft spot for Texas Instruments’s C2000 line, which is currently in the Piccolo and Delfino incarnations. The 16-bit byte is horrible (especially if you need to port code to another processor), but somehow everything else about the DSP does just what I want. Although, it may not be about the processor itself: if I’m using a DSP, I must be doing something mathy and I like math.

NAN: Do you have any predictions for upcoming “hot topics?”

ELECIA: I’m most excited about health monitoring. I’m surprised that Star Trek and other science fiction sources got tricorders right but missed the constant health monitoring we are heading toward with the rise of wearables and the interest in quantified self.
I’m most concerned about connectivity. The Internet of Things (IoT) is definitely coming, but many of these devices seem to be more about applying technology to any device that can stand the price hit, whether it makes sense or not.

Worse, the methods for getting devices connected keeps fracturing as the drive toward low-cost and high functionality leads the industry in different directions. And even worse, the ongoing battle between security and ease of use manages to give us things that are neither usable nor secure. There isn’t a good solution (yet). To make progress we need to consider the application, the user, and what they need instead of applying what we have and hoping for the best.

# 3-D Integration Impact and Challenges

People want transistors—lots of them. It pretty much doesn’t matter what shape they’re in, how small they are, or how fast they operate. Simply said, the more the merrier. Diversity is also good. The more different the transistors, the more useful and interesting the product. And without any question, the cheaper the transistors, the better. So the issue is, how best to achieve as many diverse transistors at the lowest cost possible.

One approach is more chips. Placing a lot of chips close together on a small board will produce a system with many transistors. Another way is more transistors per chip. Keep on scaling the technology to provide more transistors in one or a few chips.

The third option combines these two approaches. Let’s have many chips with many transistors and end up with a huge number of transistors. However, there is a limit to this approach. It’s well understood that scaling is coming to an end. And placing multiple chips on a board can have a terrible effect on a system’s overall speed and power dissipation.

But there is an elegant and intellectually simple solution. Rather than connecting these chips horizontally across a board, connect them vertically, providing N times more transistors, where N is the number of chips stacked one above another. Such vertical, 3-D integration was first broached by William Shockley, co-inventor of the transistor at Bell Labs in 1947. Shockley described the 3-D integration concept in a 1958 patent, which was followed by Merlin Smith and Emanuel Stern’s 1967 patent outlining how best to produce the holes between layers. We now call these inter-layer holes through silicon vias (TSVs). Technology is still catching up to these 3-D concepts.

Three-dimensional integration offers exciting advantages. For example, the vertical distance between layers is much shorter than the horizontal dimensions across a chip. Three-dimensional circuits, therefore, operate faster and dissipate less power than their 2-D equivalent. A 3-D system is shockingly small, permitting it to fit much more conveniently into a tiny space. Think small portable electronics (e.g., credit cards).

But the most exciting advantage of 3-D integration isn’t the small form factor, higher speed, or lower power; it’s the natural ability to support many disparate technologies and functions as one integrated, heterogeneous system. Even better, each chip layer can be optimized for a particular function and technology, since the individual chips can each be developed in isolation. No more trading off different capabilities to combine disparate technologies on the same chip. Now we can use the absolute best technology for each layer and a completely different and optimized technology for a different layer. This approach enables all kinds of novel applications that until now couldn’t have been conceived or would have been cost-prohibitive.

Imagine placing a microprocessor plane below a MEMS-accelerometer plane below an analog plane (with ADCs) below a temperature sensor, all below a video imager (which has to be at the top to “see”). All of these planes fit together into a tiny (smaller than a fingernail) silicon cube while operating at higher speeds and dissipating lower power.

There are technical issues, including: how to best make the TSVs, how to construct the system architecture to fully exploit the system’s 3-D nature, how to deliver power across these multiple planes, how to synchronize this system to best move data around the cube, how to manage system design complexity, and much more.

Two issues rise to the top. The first is power dissipation (specifically, power density). When many transistors switch at a high rate within a tiny volume, the temperature rises, which can impair performance and reliability. I believe this issue, albeit difficult, is technically solvable and simply will require a lot of good engineering.

The real problem is cost. How do we mature this technology quickly enough to drive the costs down to a point where volume commercial applications are possible? Many companies are close to producing tangible 3-D-based products. Cubes of highly dense memory will likely be the first serious and cost-effective product. Early versions are already available. Three-dimensional integration will soon be here in a serious way with what will be a fascinating assortment of all kinds of exciting new products. You won’t have to wait too long.

# Registration Open for Sensors Expo & Conference

Thousands of engineers, scientists, and industry professionals are expected to gather for the 28th Annual Sensors Expo & Conference to assess and discuss the development and deployment of sensors and sensors systems.

The Expo & Conference will take place at The Donald E. Stephens Convention Center in Rosemont, IL, from June 25-June 26, 2014, with pre-conference symposia on June 24. Registration is now open at www.sensorsexpo.com.

This event, exclusively focused on sensor technology, will offer more than 65 technical sessions on the latest solutions to current sensing challenges while exploring the most recent sensing technologies. In addition to two full days of education sessions, attendees can participate in three full-day pre-conference symposia, taking place Tuesday, June 24.  The topics include “Designing MEMS In: How to Engage the Supply Chain,” chaired by Karen Lightman, executive director, MEMS Industry Group; “Energy Harvesting for Powering Wireless Sensors,” chaired by Randy Frank, president, Randy Frank & Associates, Ltd.; and “Making the Internet of Things a Reality: A Toolkit for Designing ‘Smart,’ ” chaired by Will Tu, ARM.

“Our team has been working diligently with our advisory board and partners to develop a stellar program offering nine tracks including Chemical & Gas Sensing, Energy Harvesting for Sensor Applications, Internet of Things, M2M, MEMS, Novel Approaches to Measurement and Detection, Power Management for Sensing Applications, Sensors @ Work, and Wireless, in addition to an expanded trade show floor offering hundreds of top vendors in the industry,” said Wendy Loew, group show director.

Conference program topics include smart power grid monitoring, the future of mobile intelligence with sensor fusion, sensors conditioning, challenges of high temperature sensing, and what you need to know to make your product a success. The Expo Hall provides access to suppliers along with information and education on their sensing products and solutions.

In the Expo Hall, attendees will see the latest sensing technologies and solutions, identify new ways to improve products and expand their functionalities using sensors, and learn about “hot” and cutting-edge technology areas. The Expo Hall will feature exhibitors including Analog Devices, Anaren, GridConnect, Microchip Technology, Mouser Electronics, Parker-Hannifin Corporation, Rowebots, STMicroelectronics, and Wyless.

# Q&A: Stephan Lubbers (Sensory Innovation)

Stephan Lubbers enjoys sensing technology. He is a creative engineer and inventor whose designs often build on his need to monitor data and figure out how things work. Steve and I recently discussed some of his designs, his contest-entry process, his thoughts on the future of embedded technology, and what’s currently happening on his workbench.—Nan Price, Associate Editor

NAN: Where are you located?

Stephan Lubbers in his workspace

STEVE: I live in Dayton, OH.

NAN: Where did you go to school and what did you study?

STEVE: My formal education is a BS in Computer Science from Wright State University, Fairborn, OH. Outside of schools, I’ve taught myself many things ranging from radio electronics to achieving an extra class amateur radio license, to assorted computer languages, to FPGA programming—all from just sitting down and saying, “Let’s learn this.”

STEVE: I am employed as a Senior Software Engineer at Beijing West Industries, where I develop embedded systems that go under the hood of high-end automobiles. (BWI is the owner of what was once General Motors’s Suspension and Brakes components company.) If your “Service Vehicle Soon” light comes on, I may have written the code behind it.

STEVE: My technical interests fall into two categories. I like to build systems around new sensing technologies and I build systems to support ham radio.

I never really thought about specific technical interests until I was asked this question. Looking at the Circuit Cellar contests I’ve entered and exploring my parts closet, I discovered that I have an abundance of sensors and sensor systems. When a new sensing device comes out, I often get one, play with it, and then look around for something to do with it. That usually results in an invention of some kind. I’ve analyzed the motion of rodeo bulls and dogs with microelectromechanical (MEMS) accelerometers, tracked eyeball movements with optical sensors, and computed automobile speeds using both GPS and microwave electronics. I don’t know if it is cause or effect, but I was always amazed by the “tricorder” on Star Trek. Do I like sensors because of Scotty and Mr. Spock? Or did I watch Star Trek because of the gadgets? I don’t know.

My love of electronics led me to amateur radio at a young age. I wasn’t as much interested in talking to other people as I was in exploring the technology that enables people to talk. I had a little success building RF devices but found that I had a real knack for digital systems. I’ve used that ability to create satellite tracking controllers, antenna switchers, and computer-to-radio interfaces.

NAN: How long have you been reading Circuit Cellar?

STEVE: I’ve subscribed to Circuit Cellar since Issue 1. I still believe the tagline that said “Inside the Box Still Counts.”

NAN: You’ve written four articles for Circuit Cellar. Some focus on data logging, monitoring, and analysis. For example, your article “Precision Motion-Sensing System Analyzer” (Circuit Cellar 192, 2006) is about a microcontroller-based, motion-sensing system for bull riders. What inspired you to create this system?

STEVE: Several things came together to spark the creation of the “Precision Motion-Sensing System Analyzer,” a.k.a. the BuckyMeter. I had already begun work on a motion-logging system but had no clear goal in mind. Shortly after the logger started working, Circuit Cellar announced its 2005 design contest. I had a short-term goal of entering the contest with my data logger. But what should I log?

My dad provided the suggestion to strap the logger onto the back of a rodeo bull. My parents had become fascinated by the sport of professional bull riding and thought it would be fun to get behind the scenes by doing this science experiment. One of the questions I had when designing the system was: “What kind of maximum G force can I expect to see?” Nobody had an answer, but the doctors responsible for repairing bull riders thought it was an interesting question. They, too, wanted to know that answer. That question opened a few doors to give us access to some bulls. EE Times printed a humorous article about my experience strapping an electronic device on the back of 1,200 lb of angry cow. It was definitely an experience!

The BuckyMeter hardware went through several iterations. In the end, an off-the-shelf Motorola Z-Star evaluation module could be used to instrument the bull with the added bonus of wireless data logging.

The project died out after a trip to instrument competition-grade bulls from American Bucking Bull, Inc. (ABBI). In hindsight, I learned an important lesson about managing customer expectations. I went to Oklahoma on a mission to collect data and try out an engineering prototype. I think the people I met with were expecting to see a polished product. Their impression, after our meeting, was that an electronic scoring aid was too slow and too complicated.

NAN: Another article, “Electronic Data Logging and Analysis: A How-To Guide for Building a Seizure-Monitoring System” (Circuit Cellar 214, 2008), describes an Atmel ATmega32-based electronic monitoring system that enables pet owners and vets to monitor epileptic seizure patterns in dogs. How does the microcontroller factor into the design?

STEVE: My seizure monitor was an offshoot of the rodeo bull motion-sensing system. The original processor had way more power than was needed and it was difficult to hand solder the part. With a working baseline from the BuckyMeter, it was easy to pick a different chip to work with. I had some experience with Atmel AVRs from a previous Circuit Cellar contest, so I looked at its product line. I had a good estimate for RAM/ROM requirements, and I decided it would be nice to have additional SPI channels to interface with the accelerometers. That led to the selection of the ATmega32. It didn’t hurt that another Atmel contest popped up in 2006 when I was in the middle of the design.

I have always wanted to expand my data beyond a single patient to see if my theory held up, so I supplied systems to some other people with epileptic dogs. This required continuous design updates mostly to keep up with outdated parts. Unfortunately, I never got any data back from the systems I gave away. My pet (and science guinea pig) passed away a few years ago, so I don’t have a subject to continue with this project.

NAN: At the end of your article, “Doppler Radar Design” (Circuit Cellar 243, 2010), you note that upgrades to the project (e.g., an enclosure and a portable power supply) could make the system “an easy-to-use mobile device.” Tell us about the design. Did you end up implementing any of those upgrades?

STEVE: Doppler Radar Design has been my most popular project. I get e-mails all the time asking how to reproduce it. As I stated in the article, the RF section is now hard to come by and expensive. Not being an RF engineer, I haven’t been able to recommend replacement parts.

The project started when my dad loaned me the microwave electronics to play with. He had wired them up for two-way ham radio communications. I couldn’t manage to make any radio contact with anybody but myself, so I started looking for other experiments to perform. In one of the experiments, I learned how to make a motion detector. From that, I decided to try to turn the project into a speed radar.

This project took help from a lot of other people because I really didn’t know what I was doing. Some radar discussions on the Internet outlined the basic design for Doppler speed radar, so I followed the suggestions, essentially a transmitter/receiver pair supplied by my borrowed Gunnplexer and a frequency detector (FFT) to show the Doppler shift of the returned signal. Accounting for the radio frequency in use gives you the speed of the reflected target, which in my case was a car.

When I discovered Ramsey Electronics sells a radar kit for \$100, I decided that my Doppler radar was really just a science experiment. It was educational for me, but for everyone who contacted me just wanting to have their own radar, the Ramsey option was cheaper, more accurate, and already packaged for portability.

I did get some helpful hints from Alan Rutz at SHF Microwave Parts Company, who suggested something called a dielectric resonator oscillator (DRO) could be used in place of the Gunnplexer I used. The advantage of his approach is that DROs are available and cost about \$20. I have not yet been successful with this upgrade.

NAN: The Renesas Electronics RX62N development board is at the heart of your KartTracker’s monitoring system (“KartTracker: A GPS-Based Vehicle Timing & Monitoring System,” Circuit Cellar 259, 2012). Tell us about the design and how the KartTracker functions.

KartTracker: A GPS-Based Vehicle Timing & Monitoring System

STEVE: The KartTracker came about one day when the neighborhood NASCAR fans went out racing karts. We wondered how fast we went, so the local engineer (me) set about finding out.

I started with a GPS receiver and a data logger and drove around the track to see what happened. As it turns out, GPS receivers automatically give you your speed! That was too easy, so I started looking for more features.

The next couple of races I watched, I tried to pay attention to more than just the action and saw that teams were very concerned with lap times. Well, I could time my laps, but that didn’t seem very interesting or complicated enough. Then I saw a qualifying session where the TV showed a continuous real-time comparison between two cars. That seemed cool! If I could build that, I could race myself to see if I was doing better or worse.

So, the KartTracker concept was born. A GPS receiver feeds continuous position data into a Renesas RX62N board. The software continuously compares my time at some location against the last time I was there. It’s like looking at the lap time, but it updates every couple of seconds so you have continuous feedback.

All the timing data is retained so later we can compare times against each other and brag about who went the fastest. I would like to broadcast the times back to the spectators, but that radio is a project for another day.

NAN: You received an Honorable Mention for your 2010 Texas Instruments DesignStellaris Design Contest entry, “Hands-Free USB Mouse.” Tell us about the project and your contest-entry process.

2010 Texas Instruments DesignStellaris Design Contest Honorable Mention “Hands-Free USB Mouse”

STEVE: My eyePOD hands-free USB Mouse is a head-mounted motion sensor that controls the mouse cursor on a PC. By moving your head, the mouse moves around the screen. You wink your eyes to click the mouse buttons. The goal was to produce a PC interface for someone who couldn’t use a typical mouse, with a secondary goal of teaching me about USB. There are some problems in certain lighting conditions, but overall it works pretty well.

After about a dozen contest entries, I have a bit of a process for creating an entry. I hope I don’t hurt my future chances by sharing my secrets, but since you asked, three things need to line up for me to start a project (contest or otherwise): I need an idea, I need some technology, and I need motivation.

Author James Rollins says, “Don’t ask where the ideas come from.” But, if you have to know, his story ideas come from a box. My contest ideas come from a little red notebook. In reality, we don’t know where the actual ideas come from, but when we get ideas we put them in the box (or book) and make a withdrawal when we need to use an idea.

Part two is that there needs to be a technology that will support the idea. I couldn’t build a rodeo bull monitor until there were cheap accelerometers available. I couldn’t build the KartTracker without a GPS. So, keep a list of technologies you like in your box of ideas.

Finally, you need motivation to execute the project. At work, your boss provides the motivation in the form of a paycheck. At home, you might have a dog that needs help or a neighbor who supplies beer for the answer of how fast his kart is. When I put the three pieces together, I have the starting point for a project. Apply your abilities and start building.

The only biggie after that is time management. Somewhere there is a deadline you need to meet. Do consistent work on your project and prioritize what needs to be done. I have a knack for drawing a line through the critical parts of a project to make sure I have something working when the end is near. You can always go back and improve a working project, but if you have too many half-built features, you have nothing to fall back on when time runs out. A good example is the radio link for the KartTracker. Without GPS and timing software, the project would be nothing. When I had time remaining, I added file I/O and data storage on an SD card. Nice features, but they weren’t necessary to demonstrate the project. The radio link fell by the wayside when entry time came up.

Finally, don’t forget the book report at the end. The judges need to know what you did, so you need to write about it. Who knows? Circuit Cellar might like what you wrote and decide to turn it into an article.

NAN: Have you recently purchased any embedded technology tools to help you with your data logging, monitoring, and analysis projects?

STEVE: My most recent tech purchase was an iPod Touch funded from a recent Circuit Cellar publication. Before you say, “That’s not embedded,” let me explain. I tend to make the user interfaces to my projects simple and to the point. Circuit Cellar contest deadlines don’t lend themselves to creating a new fancy interface for each project. Instead, I would offload debugging, control, and extra features to an external system. I started out using RS-232 serial to a PC. For portability and speed, I moved to a PalmPilot with an infrared data access  (IrDA) interface. A Bluetooth or Wi-Fi interface seems like a logical progression to me. The iPod Touch has these interfaces and it leaves me with a new gadget to play with.

A more embedded acquisition is the Texas Instruments MetaWatch. If you haven’t seen one of these, it’s a stylish digital watch that talks to your smartphone. For the more adventurous, the source code is available so you can add your own features. There must be something great that I can do with a wrist-mounted computer, I just haven’t had the “ah-ha” moment yet.

NAN: Are you currently working on or planning any embedded-design-related projects?

STEVE: I call my current project the SeeingEye for a dog. The blind have used guide dogs since the 16th century. That’s a huge debt man owes his best friend! To help repay that debt, I’m creating a twist on the seeing eye dog by creating a seeing eye for a friend’s vision-impaired dog. Using the sensors and technology robots use for collision avoidance, the SeeingEye will detect obstacles in a dog’s path. The trick seems to be the user interface to convey the collision avoidance information and training the dog to respond correctly to the stimulus. I figure if microchips in robots can learn to avoid walls, then puppy neurons should be able to do the same thing. I still have more work to do to figure out how to get the sensor to stay in place.

SeeingEye for dogs, circuit board

SeeingEye for dogs, in “use”

NAN: Do you have any thoughts on the future of embedded technology?

STEVE: As a builder of embedded systems, I am amazed at all of the things we can do with high-speed processors and multiple megabytes of memory. It seems like if we can imagine it, we can build it.

As a user of embedded technologies, it sometimes seems like the engineers are trying to be too clever by stuffing anything they can into the box whether those features are needed or not.

The complexity of some devices has skyrocketed to the point that stability has been affected and users don’t know what features they have or how to use them. We now take for granted a constant stream of software updates to our devices and press reset when it doesn’t work as desired.

Einstein is credited with saying, “Everything should be made as simple as possible, but no simpler.” I’d like to see the industry adopt Einstein’s advice and the “Keep it simple, stupid!” (KISS) principle to help us manage the growing complexities. We’d spend less time serving our devices by trying to make them work and more time being served by our devices as they flawlessly do the work we want done.

# CC267: Continuity of Embedded Tech Content

The October issue features articles on topics ranging from FAT cache to IIR digital filters to a quadcopter that uses a mechanical gyro. Let’s review.

Jeff’s quadcopter uses a mechanical gyro that is “an inexpensive yet elegant attempt to counteract wind gusts.” With its protective shield removed, you can see the motorized spinning rotor that sustains equilibrium as its frame moves.

On page 16, Stuart Oliver details how to use math routines that include the dsPIC hardware features, such as the accumulators and barrel shifter. He uses the math for implementing Assembler routines.

Turn to page 30 to learn how Kerry Imming uses FAT cache for SD card access. You can implement his cache technique in a variety of other applications.

Before you start a new project, familiarize yourself George Novacek’s tips on managing project risk (p. 34). He explains how to define, evaluate, and handle risk. Better yet, why not just reduce risk by avoiding as many problems as possible?

Bob Japenga addresses this issue as well (p. 38). In the third part of his series on concurrency in embedded systems, he details how to avoid concurrency-related problems, which can be difficult because the more concurrency you add to a project, the more complicated it becomes.

Ed Nisley presented a MOSFET tester in his August 2012 article, “MOSFET Channel Resistance.” In this issue, Ed covers temperature measurement, the control circuitry, the firmware’s proportional integral control loop, and more (p. 42).

A fan under the black CPU heatsink keeps it near ambient temperature, so that the Peltier module under the aluminum block can control the MOSFET temperature. The gray epoxy block holds a linearized thermistor circuit connected to the Arduino microcontroller under the PCB. (Source: E. Nisley)

Check out Robert Lacoste’s article on page 58 for an introduction to IIR digital filters. You’ll learn about the differences between IIR filters, FIR filters, and analog filters.

WinFilter allows you to calculate and simulate all kind of IIR filters just by entering their key characteristics (left). The plots shows you the resulting frequency and time behavior. (Source: R. Lacoste)

Working with an unstable mechanical gyro? As Jeff Bachiochi explains, a MEMS system is the solution (p. 68).

Lastly, check out the interview with Helen Li on page 54. You’ll find her impressive research exciting and inspirational.