Transform IoT Audio, Voice, and Video Interactions

NXP Semiconductors (now part of Qualcomm) recently introduced the new i.MX 8M family of applications processors specifically designed to meet increasing audio and video system requirements for smart home and smart mobility applications such as over-the-top (OTT) set-top boxes, digital media adapters, surround sound, sound bars, A/V receivers, voice control, voice assistance, digital signage, and general-purpose human machine interface (HMI) solutions.NXP-iMX8M-FS

The concept of the smart home is expanding rapidly, heightening consumers’ expectations for audio and video entertainment and transforming the requirements for consumer electronics devices. NXP’s i.MX 8M family addresses the major inflection points currently underway in streaming media: voice recognition and networked speakers in audio, and the move to 4K High Dynamic Range (HDR) and the growth of smaller, more compact form factors in video.

NXP’s i.MX 8M family of processors has up to four 1.5-GHz ARM Cortex-A53 and Cortex-M4 cores, flexible memory options and high-speed connectivity interfaces. The processors also feature full 4K UltraHD resolution and HDR (Dolby Vision, HDR10 and HLG) video quality, the highest levels of pro audio fidelity, up to 20 audio channels and DSD512 audio. The i.MX 8M family is tailored to streaming video devices, streaming audio devices and voice control applications.

Capable of driving dual displays, the new devices include:

  • The i.MX 8M Dual/i.MX 8M Quad, which integrates two or four ARM Cortex-A53 cores, one Cortex- M4F core, a GC7000Lite GPU and 4kp60, h.265 and VP9 video capability.
  • The i.MX 8M QuadLite, which integrates four ARM Cortex-A53 cores, one Cortex- M4F core and a GC7000Lite GPU.
  • The i.MX 8M Solo, which integrates one ARM Cortex-A53 core, one Cortex-M4F core and a GC7000nanoULTRA GPU.

The i.MX 8 applications processor is highly scalable with a pin- and power-compatible package and comprehensive software support. The i.MX 8 multi-sensory enablement kit (MEK) is now available to prototype i.MX 8M systems. Limited sampling of i.MX 8M will begin in the second quarter of 2017, and general availability is expected in the fourth quarter of 2017.

Source: NXP Semiconductors

Boldport Club: Behind the Scenes

We first met London-based engineer Saar Drimer in December 2015. At that time, his was running Boldport—a hardware and prototyping consultancy that specializes in circuit boards—from a workspace was in one of the characteristic arches underneath London Bridge Station. A lot has changed since then. Today, Drimer has a new workspace and he is running Boldport Club, which is a monthly electronics hardware subscription service. We recently met up with him to discuss his work and newest endeavors.

“The big change is the club I started early this year,” Drimer explained. “I posted my initial ideas online and the response was very promising, around 170 members signed up in the first month.”

N. Mittal’s Dorm Room-Based Workspace in Bombay

The workspaces we see in Circuit Cellar are fascinating. The engineers who open up their rooms, garages, and cellar’s normally have a lot of equipment and sufficient access to components and facilities. But what about an Indian university student’s workspace? Wisse Hettinga recently visited with Nishant Mittal, a student at the Indian Institute of Technology (IIT Bombay). Mittal discussed his small workspace space in his dorm room, as well as his plans for the future.

Q&A: Jeremy Blum, Electrical Engineer, Entrepreneur, Author

Jeremy Blum

Jeremy Blum

Jeremy Blum, 23, has always been a self-proclaimed tinkerer. From Legos to 3-D printers, he has enjoyed learning about engineering both in and out of the classroom. A recent Cornell University College of Engineering graduate, Jeremy has written a book, started his own company, and traveled far to teach children about engineering and sustainable design. Jeremy, who lives in San Francisco, CA, is now working on Google’s Project Glass.—Nan Price, Associate Editor

NAN: When did you start working with electronics?

JEREMY: I’ve been tinkering, in some form or another, ever since I figured out how to use my opposable thumbs. Admittedly, it wasn’t electronics from the offset. As with most engineers, I started with Legos. I quickly progressed to woodworking and I constructed several pieces of furniture over the course of a few years. It was only around the start of my high school career that I realized the extent to which I could express my creativity with electronics and software. I thrust myself into the (expensive) hobby of computer building and even built an online community around it. I financed my hobby through my two companies, which offered computer repair services and video production services. After working exclusively with computer hardware for a few years, I began to dive deeper into analog circuits, robotics, microcontrollers, and more.

NAN: Tell us about some of your early, pre-college projects.

JEREMY: My most complex early project was the novel prosthetic hand I developed in high school. The project was a finalist in the prestigious Intel Science Talent Search. I also did a variety of robotics and custom-computer builds. The summer before starting college, my friends and I built a robot capable of playing “Guitar Hero” with nearly 100% accuracy. That was my first foray into circuit board design and parallel programming. My most ridiculous computer project was a mineral oil-cooled computer. We submerged an entire computer in a fish tank filled with mineral oil (it was actually a lot of baby oil, but they are basically the same thing).

DeepNote Guitar Hero Robot

DeepNote Guitar Hero Robot

Mineral Oil-Cooled Computer

Mineral Oil-Cooled Computer

NAN: You’re a recent Cornell University College of Engineering graduate. While you were there, you co-founded Cornell’s PopShop. Tell us about the workspace. Can you describe some PopShop projects?

Cornell University's PopShop

Cornell University’s PopShop

JEREMY: I recently received my Master’s degree in Electrical and Computer Engineering from Cornell University, where I previously received my BS in the same field. During my time at Cornell, my peers and I took it upon ourselves to completely retool the entrepreneurial climate at Cornell. The PopShop, a co-working space that we formed a few steps off Cornell’s main campus, was our primary means of doing this. We wanted to create a collaborative space where students could come to explore their own ideas, learn what other entrepreneurial students were working on, and get involved themselves.

The PopShop is open to all Cornell students. I frequently hosted events there designed to get more students inspired about pursuing their own ideas. Common occurrences included peer office hours, hack-a-thons, speed networking sessions, 3-D printing workshops, and guest talks from seasoned venture capitalists.

Student startups that work (or have worked) out of the PopShop co-working space include clothing companies, financing companies, hardware startups, and more. Some specific companies include Rosie, SPLAT, LibeTech (mine), SUNN (also mine), Bora Wear, Yorango, Party Headphones, and CoVenture.

NAN: Give us a little background information about Cornell University Sustainable Design (CUSD). Why did you start the group? What types of CUSD projects were you involved with?

CUSD11JEREMY: When I first arrived at Cornell my freshman year, I knew right away that I wanted to join a research lab, and that I wanted to join a project team (knowing that I learn best in hands-on environments instead of in the classroom). I joined the Cornell Solar Decathlon Team, a very large group of mostly engineers and architects who were building a solar-powered home to enter in the biannual solar decathlon competition orchestrated by the Department of Energy.

By the end of my freshman year, I was the youngest team leader in the organization.  After competing in the 2009 decathlon, I took over as chief director of the team and worked with my peers to re-form the organization into Cornell University Sustainable Design (CUSD), with the goal of building a more interdisciplinary team, with far-reaching impacts.


Under my leadership, CUSD built a passive schoolhouse in South Africa (which has received numerous international awards), constructed a sustainable community in Nicaragua, has been the only student group tasked with consulting on sustainable design constraints for Cornell’s new Tech Campus in New York City, partnered with nonprofits to build affordable homes in upstate New York, has taught workshops in museums and school, contributed to the design of new sustainable buildings on Cornell’s Ithaca campus, and led a cross-country bus tour to teach engineering and sustainability concepts at K–12 schools across America. The group is now comprised of students from more than 25 different majors with dozens of advisors and several simultaneous projects. The new team leaders are making it better every day. My current startup, SUNN, spun out of an EPA grant that CUSD won.

CUSD7NAN: You spent two years working at MakerBot Industries, where you designed electronics for a 3-D printer and a 3-D scanner. Any highlights from working on those projects?

JEREMY: I had a tremendous opportunity to learn and grow while at MakerBot. When I joined, I was one of about two dozen total employees. Though I switched back and forth between consulting and full-time/part-time roles while class was in session, by the time I stopped working with MakerBot (in January 2013), the company had grown to more than 200 people. It was very exciting to be a part of that.

I designed all of the electronics for the original MakerBot Replicator. This constituted a complete redesign from the previous electronics that had been used on the second generation MakerBot 3-D printer. The knowledge I gained from doing this (e.g., PCB design, part sourcing, DFM, etc.) drastically outweighed much of what I had learned in school up to that point. I can’t say much about the 3-D scanner (the MakerBot Digitizer), as it has been announced, but not released (yet).

The last project I worked on before leaving MakerBot was designing the first working prototype of the Digitizer electronics and firmware. These components comprised the demo that was unveiled at SXSW this past April. This was a great opportunity to apply lessons learned from working on the Replicator electronics and find ways in which my personal design process and testing techniques could be improved. I frequently use my MakerBot printers to produce custom mechanical enclosures that complement the open-source electronics projects I’ve released.

NAN: Tell us about your company, Blum Idea Labs. What types of projects are you working on?

JEREMY: Blum Idea Labs is the entity I use to brand all my content and consulting services. I primarily use it as an outlet to facilitate working with educational organizations. For example, the St. Louis Hacker Scouts, the African TAHMO Sensor Workshop, and several other international organizations use a “Blum Idea Labs Arduino curriculum.” Most of my open-source projects, including my tutorials, are licensed via Blum Idea Labs. You can find all of them on my blog ( I occasionally offer private design consulting through Blum Idea Labs, though I obviously can’t discuss work I do for clients.

NAN: Tell us about the blog you write for element14.

JEREMY: I generally use my personal blog to write about projects that I’ve personally been working on.  However, when I want to talk about more general engineering topics (e.g., sustainability, engineering education, etc.), I post them on my element14 blog. I have a great working relationship with element14. It has sponsored the production of all my Arduino Tutorials and also provided complete parts kits for my book. We cross-promote each-other’s content in a mutually beneficial fashion that also ensures that the community gets better access to useful engineering content.

NAN: You recently wrote Exploring Arduino: Tools and Techniques for Engineering Wizardry. Do you consider this book introductory or is it written for the more experienced engineer?

JEREMY: As with all the video and written content that I produce on my website and on YouTube, I tried really hard to make this book useful and accessible to both engineering veterans and newbies. The book builds on itself and provides tons of optional excerpts that dive into greater technical detail for those who truly want to grasp the physics and programming concepts behind what I teach in the book. I’ve already had readers ranging from teenagers to senior citizens comment on the applicability of the book to their varying degrees of expertise. The Amazon reviews tell a similar story. I supplemented the book with a lot of free digital content including videos, part descriptions, and open-source code on the book website.

NAN: What can readers expect to learn from the book?

JEREMY: I wrote the book to serve as an engineering introduction and as an idea toolbox for those wanting to dive into concepts in electrical engineering, computer science, and human-computer interaction design. Though Exploring Arduino uses the Arduino as a platform to experiment with these concepts, readers can expect to come away from the book with new skills that can be applied to a variety of platforms, projects, and ideas. This is not a recipe book. The projects readers will undertake throughout the book are designed to teach important concepts in addition to traditional programming syntax and engineering theories.

NAN: I see you’ve spent some time introducing engineering concepts to children and teaching them about sustainable engineering and renewable energy. Tell us about those experiences. Any highlights?

JEREMY: The way I see it, there are two ways in which engineers can make the world a better place: they can design new products and technologies that solve global problems or they can teach others the skills they need to assist in the development of solutions to global problems. I try hard to do both, though the latter enables me to have a greater impact, because I am able to multiply my impact by the number of students I teach. I’ve taught workshops, written curriculums, produced videos, written books, and corresponded directly with thousands of students all around the world with the goal of transferring sufficient knowledge for these students to go out and make a difference.

Here are some highlights from my teaching work:


I taught BlueStamp Engineering, a summer program for high school students in NYC in the summer of 2012. I also guest-lectured at the program in 2011 and 2013.

I co-organized a cross-country bus tour where we taught sustainability concepts to school children across the country.

indiaI was invited to speak at Techkriti 2013 in Kanpur, India. I had the opportunity to meet many students from IIT Kanpur who already followed my videos and used my tutorials to build their own projects.

Blum Idea Labs partnered with the St. Louis Hacker Scouts to construct a curriculum for teaching electronics to the students. Though I wasn’t there in person, I did welcome them all to the program with a personalized video.

brooklyn_childrens_zoneThrough CUSD, I organized multiple visits to the Brooklyn Children’s Zone, where my team and I taught students about sustainable architecture and engineering.

Again with CUSD, we visited the Intrepid museum to teach sustainable energy concepts using potato batteries.


NAN: Speaking of promoting engineering to children, what types of technologies do you think will be important in the near future?

JEREMY: I think technologies that make invention more widely accessible are going to be extremely important in the coming years. Cheaper tools, prototyping platforms such as the Arduino and the Raspberry Pi, 3-D printers, laser cutters, and open developer platforms (e.g., Android) are making it easier than ever for any person to become an inventor or an engineer.  Every year, I see younger and younger students learning to use these technologies, which makes me very optimistic about the things we’ll be able to do as a society.

Programmable Logic Video Lessons

Interested in learning more about programmable logic? You’re in luck. Colin O’Flynn’s first article in his “Programmable Logic in Practice” column appears in Circuit Cellar’s October 2013 issue. To accompany his work, Colin is producing informative videos for you to view after reading his articles.

In the first video, Colin covers the topic of adding the Xilinx ChipScope ILA/VIO core using automatic and manual insertion with ISE.


Since 2002, Circuit Cellar has published several of O’Flynn’s articles. O’Flynn  is an engineer and lecturer at Dalhousie University in Halifax, Nova Scotia. He earned a Master’s in applied science from Dalhousie and pursued further graduate studies in cryptographic systems. Over the years, he has developed a wide variety of skills ranging from electronic assembly (including SMDs) to FPGA design in Verilog and VHDL to high-speed PCB design.

Dual-Channel 3G-SDI Video/Audio Capture Card


ADLINK PCIe-2602 Video/Audio Capture Card

The PCIe-2602 is an SDI video/audio capture card that supports all SD/HD/3G-SDI signals and operates at six times the resolution of regular VGA connections. The card also provides video quality with lossless full color YUV 4:4:4 images for sharp, clean images.

The PCIe-2602 is well suited for medical imaging and intelligent video surveillance and analytics. With up to 12-bit pixel depth, the card  provides extreme image clarity and smoother transitions from color-to-color enhance image detail to support critical medical imaging applications, including picture archiving and communication system (PACS) endoscopy and broadcasting.

The card’s features include low latency uncompressed video streaming, CPU offloading, and support for high-quality live viewing for video analytics of real-time image acquisition, as required in casino and defense environments. PCIe-2602 signals can be transmitted over 100 m when combined with a 75-Ω coaxial cable.

The PCIe-2602 is equipped with RS-485 and digital I/O. It accommodates external devices (e.g., PTZ cameras and sensors) and supports Windows 7/XP OSes. The card comes with ADLINK’s ViewCreator Pro utility to enable setup, configuration, testing, and system debugging without any software programming. All ADLINK drivers are compatible with Microsoft DirectShow.

Contact ADLINK for pricing.

ADLINK Technology, Inc.

CC269: Break Through Designer’s Block

Are you experiencing designer’s block? Having a hard time starting a new project? You aren’t alone. After more than 11 months of designing and programming (which invariably involved numerous successes and failures), many engineers are simply spent. But don’t worry. Just like every other year, new projects are just around the corner. Sooner or later you’ll regain your energy and find yourself back in action. Plus, we’re here to give you a boost. The December issue (Circuit Cellar 269) is packed with projects that are sure to inspire your next flurry of innovation.

Turn to page 16 to learn how Dan Karmann built the “EBikeMeter” Atmel ATmega328-P-based bicycle computer. He details the hardware and firmware, as well as the assembly process. The monitoring/logging system can acquire and display data such as Speed/Distance, Power, and Recent Log Files.

The Atmel ATmega328-P-based “EBikeMeter” is mounted on the bike’s handlebar.

Another  interesting project is Joe Pfeiffer’s bell ringer system (p. 26). Although the design is intended for generating sound effects in a theater, you can build a similar system for any number of other uses.

You probably don’t have to be coerced into getting excited about a home control project. Most engineers love them. Check out Scott Weber’s garage door control system (p. 34), which features a MikroElektronika RFid Reader. He built it around a Microchip Technology PIC18F2221.

The reader is connected to a breadboard that reads the data and clock signals. It’s built with two chips—the Microchip 28-pin PIC and the eight-pin DS1487 driver shown above it—to connect it to the network for testing. (Source: S. Weber, CC269)

Once considered a hobby part, Arduino is now implemented in countless innovative ways by professional engineers like Ed Nisley. Read Ed’s article before you start your next Arduino-related project (p. 44). He covers the essential, but often overlooked, topic of the Arduino’s built-in power supply.

A heatsink epoxied atop the linear regulator on this Arduino MEGA board helped reduce the operating temperature to a comfortable level. This is certainly not recommended engineering practice, but it’s an acceptable hack. (Source: E. Nisley, CC269)

Need to extract a signal in a noisy environment? Consider a lock-in amplifier. On page 50, Robert Lacoste describes synchronous detection, which is a useful way to extract a signal.

This month, Bob Japenga continues his series, “Concurrency in Embedded Systems” (p. 58). He covers “the mechanisms to create concurrently in your software through processes and threads.”

On page 64, George Novacek presents the second article in his series, “Product Reliability.” He explains the importance of failure rate data and how to use the information.

Jeff Bachiochi wraps up the issue with a article about using heat to power up electronic devices (p. 68). Fire and a Peltier device can save the day when you need to charge a cell phone!

Set aside time to carefully study the prize-winning projects from the Reneas RL78 Green Energy Challenge (p. 30). Among the noteworthy designs are an electrostatic cleaning robot and a solar energy-harvesting system.

Lastly, I want to take the opportunity to thank Steve Ciarcia for bringing the electrical engineering community 25 years of innovative projects, essential content, and industry insight. Since 1988, he’s devoted himself to the pursuit of EE innovation and publishing excellence, and we’re all better off for it. I encourage you to read Steve’s final “Priority Interrupt” editorial on page 80. I’m sure you’ll agree that there’s no better way to begin the next 25 years of innovation than by taking a moment to understand and celebrate our past. Thanks, Steve.

DIY 10.1˝ Touchscreen Home Control System

Domotics (home automation) control systems are among the most innovative and rewarding design projects creative electrical engineers can undertake. Let’s take a look at an innovative Beagle Board-based control system that enables a user to control lights with a 10.1˝ capacitive touchscreen.

Domotics control system

The design features the following modules:

• An I/O board for testing purposes
• An LED strip board for controlling an RGB LED strip
• A relay board for switching 230-VAC devices
• An energy meter for measuring on/off (and also for logging)

ELektor editor and engineer Clemens Valens recently interviewed Koen van Dongen about the design. Van Dongen describes the system’s electronics and then demonstrates how to use the touchscreen to control a light and LED strip.

As Valens explains suggests, it would be a worthwhile endeavor to incorporate a Wi-Fi connection to enable cellphone and tablet control. If you build such system, be sure to share it with our staff. Good luck! is an Elektor International Media website.

DIY Solar-Powered, Gas-Detecting Mobile Robot

German engineer Jens Altenburg’s solar-powered hidden observing vehicle system (SOPHECLES) is an innovative gas-detecting mobile robot. When the Texas Instruments MSP430-based mobile robot detects noxious gas, it transmits a notification alert to a PC, Altenburg explains in his article, “SOPHOCLES: A Solar-Powered MSP430 Robot.”  The MCU controls an on-board CMOS camera and can wirelessly transmit images to the “Robot Control Center” user interface.

Take a look at the complete SOPHOCLES design. The CMOS camera is located on top of the robot. Radio modem is hidden behind the camera so only the antenna is visible. A flexible cable connects the camera with the MSP430 microcontroller.

Altenburg writes:

The MSP430 microcontroller controls SOPHOCLES. Why did I need an MSP430? There are lots of other micros, some of which have more power than the MSP430, but the word “power” shows you the right way. SOPHOCLES is the first robot (with the exception of space robots like Sojourner and Lunakhod) that I know of that’s powered by a single lithium battery and a solar cell for long missions.

The SOPHOCLES includes a transceiver, sensors, power supply, motor
drivers, and an MSP430. Some block functions (i.e., the motor driver or radio modems) are represented by software modules.

How is this possible? The magic mantra is, “Save power, save power, save power.” In this case, the most important feature of the MSP430 is its low power consumption. It needs less than 1 mA in Operating mode and even less in Sleep mode because the main function of the robot is sleeping (my main function, too). From time to time the robot wakes up, checks the sensor, takes pictures of its surroundings, and then falls back to sleep. Nice job, not only for robots, I think.

The power for the active time comes from the solar cell. High-efficiency cells provide electric energy for a minimum of approximately two minutes of active time per hour. Good lighting conditions (e.g., direct sunlight or a light beam from a lamp) activate the robot permanently. The robot needs only about 25 mA for actions such as driving its wheel, communicating via radio, or takes pictures with its built in camera. Isn’t that impossible? No! …

The robot has two power sources. One source is a 3-V lithium battery with a 600-mAh capacity. The battery supplies the CPU in Sleep mode, during which all other loads are turned off. The other source of power comes from a solar cell. The solar cell charges a special 2.2-F capacitor. A step-up converter changes the unregulated input voltage into 5-V main power. The LTC3401 changes the voltage with an efficiency of about 96% …

Because of the changing light conditions, a step-up voltage converter is needed for generating stabilized VCC voltage. The LTC3401 is a high-efficiency converter that starts up from an input voltage as low as 1 V.

If the input voltage increases to about 3.5 V (at the capacitor), the robot will wake up, changing into Standby mode. Now the robot can work.

The approximate lifetime with a full-charged capacitor depends on its tasks. With maximum activity, the charging is used after one or two minutes and then the robot goes into Sleep mode. Under poor conditions (e.g., low light for a long time), the robot has an Emergency mode, during which the robot charges the capacitor from its lithium cell. Therefore, the robot has a chance to leave the bad area or contact the PC…

The control software runs on a normal PC, and all you need is a small radio box to get the signals from the robot.

The Robot Control Center serves as an interface to control the robot. Its main feature is to display the transmitted pictures and measurement values of the sensors.

Various buttons and throttles give you full control of the robot when power is available or sunlight hits the solar cells. In addition, it’s easy to make short slide shows from the pictures captured by the robot. Each session can be saved on a disk and played in the Robot Control Center…

The entire article appears in Circuit Cellar 147 2002. Type “solarrobot”  to access the password-protected article.

Propeller Games (P2): Game Logic

In the first part of this article series on Parallax Propeller-based gaming projects, I hooked up the hardware for the Hi/Lo game on a breadboard. Now I’ll write the game logic. The finished code is available here.

The power of the Propeller chip is in its multiple CPU cores. But you can do just fine with one processor, especially for a simple game like Hi/Lo. You program each of the processors in assembly or in the Parallax-invented SPIN high-level language. Assembly programs run blazingly fast directly in the CPU core. SPIN compiles to a binary format that is interpreted by the SPIN interpreter (written in assembly). The interpreter runs in the CPU core.

The CPU core is designed for speed, but it only has room for 512 instructions. The SPIN interpreter fetches your program byte by byte from shared RAM. Your code runs more slowly, but you have 32K of space to work with. I’ll use assembly in future projects, but SPIN is perfect for Hi/Lo.

A SPIN file is a collection of functions and data (shared by all functions in the file). The functions use local variables kept on a call stack. You break up your programming task into smaller functions that build on one another and call each other. You pass parameters to the functions and use the return values. It is all very similar to C programming though the syntax is different. The interpreter begins with the first function in your file no matter what you name it.

I started the project with a test “main” and the functions to control the Hi/Lo speaker, LEDs, and switches. 

This function plays a tone on the speaker (Source: C. Cantrell)

The “playTone” function generates a square wave on the speaker pin. The “cnt” register is a built-in 32-bit value that increments with every system clock. I run the prop stick full out with an 80-MHz clock configuration (5M-Hz crystal with a *16 internal multiplier). The “waitcnt” instruction puts the CPU to sleep until the system clock reaches the requested value. There are two waits in the loop that generates one clock cycle. Thus the generated frequency is roughly 40 MHz/freq. I say “roughly” because each instruction takes a little time to execute. The actual generated frequency is slightly less. There are much better ways to generate a precise square wave with the propeller hardware, but this is function is easy to understand, and it works fine for the simple Hi/Lo game.

The LED display is a collection of 14 segments and two dots that are turned on or off by writing a 1 or 0 to the Propeller port pins. The program use a look-up table that defines the various segment patterns to be shown.

The output pin bit patterns for numeric digits (Source: C. Cantrell)

The look-up table is defined in a data (DAT) section in the program. The SPIN language allows you to define binary constants with a “%” prefix. You can use the underscore (“_”) anywhere in any numeric constant to make it easier to read. The comment line just above the table shows how the segments map to bit positions in the propeller’s output register.

The “drawNumber” function displays a two digit value on the display. The function first divides the value by 10. The whole part (value/10) is the digit in the 10s place. The remainder (value//10) is the digit in the 1s place. The function looks up the separate patterns, ORs them together, and writes to the “outa” output register to toggle the lights.

I wrote LED functions to “drawBlank” (blank the display) and “drawHi” (show “Hi”) and “drawLo” (show “Lo”). These one-line functions are easy enough to code inline where they are used. But having the functions in distinct blocks makes the using code easier to understand and modify.

The functions to read the buttons return Boolean values: true if the switch is pressed or false if it is not. When a button is pressed, the corresponding input bit in “ina” goes to “1.” There are five buttons and five functions—one for each. There is also an “isAny” function to detect if any button is pressed.

The function returns "true" if a button is pressed. (Source: C. Cantrell)

The game itself has two distinct modes. The “splash” mode flashes “Hi/Lo” and waits for a player to press a button. This is an “attract” mode that draws players to the game. The “splash” function returns when a button has been pressed. The “playGame” function is the game logic. The function returns when the game is over. Thus the main loop simply calls the two functions in an infinite loop.

???????????. (Source: C. Cantrell)

The “splash” function calls “drawHi” and “drawLo” with a pause between.

The function attracts a player to the game. (Source: C. Cantrell)

The “pauseStopOnAnyButton” function counts up the delay and watches for “isAny”. It aborts the pause and returns true if a button is pressed. The “SPLASH_DELAY” is defined in the constant (“CON”) area of the program. I keep all “magic numbers” like delay counts and tone values in the CON area for easy tweaking.

The “playGame” function uses three helper functions: “getPlayerGuess,” “showWin,” and “showHint.” The “showWin” and “showHint” functions are just a couple of lines each and could be coded inline. Having them separate allows you to enhance the visual effects without changing the game logic code.

The “getPlayerGuess” does the real work of the game. It watches the buttons and changes the displayed number accordingly.

The function takes the player input. (Source: C. Cantrell)

The “getPlayerGuess” function is an infinite loop with five IF checks for each button. When the middle button is pressed the function returns with the global “playerGuess” variable holding the input value. The other buttons increment or decrement the digits on the display. Each IF block checks for overflow and plays a feedback tone.

There you have it: a simple Hi Lo game. The visual and input effects are in separate functions ready to be spruced up. I bet your solution has many more bells and whistles! I look forward to reading your ideas in the comments of this blog.

Next time I’ll wrap up the Hi Lo game with a little multitasking. I’ll write parallel programs to run in two new CPU cogs to manage sound effects and the LED display.

Chris Cantrell earned an MSEE from the University of Alabama. He writes Java and Flex for Emerson Network Power in Huntsville, Alabama. Circuit Cellar published 10 of his articles between 2002 and 2012: Issue 145, Issue 152, Issue 161, Issue 184, Issue 187, Issue 193, Issue 205, Issue 209, Issue 139, and Issue 260.

Propeller Games (P1): Hi Lo

Welcome to the Propeller Games! In a few installments, I’ll present several gaming projects that use the Parallax Propeller chip. The Propeller is perfect for gaming with its multiple CPU cores to handle simultaneous gaming activities and its on-board video generation circuitry.

My first game project is the classic “higher/lower” game, where the computer thinks of a number between 0 and 99 and you guess it. You have probably seen this played as the “Clock Game” on The Price is Right TV show, though some contestants struggle with a basic binary search algorithm. (You can watch videos of the game at

This entire project is built on a solderless breadboard. If you are new to the Propeller, this is the perfect project to get acquainted with the hardware and programming. If you are a Propeller guru, you will enjoy the nostalgia of gaming on LEDs and push buttons. Grab your breadboard and follow along.


What you’ll need:

  • Breadboard and wire
  • 9-VDC wall transformer
  • Parallax PropStick USB
  • Two-digit 7-segment LED display
  • Five SPST pushbuttons
  • Audio speaker
  • Sixteen 200-Ω resistors
  • Five 10-kΩ resistors

The board and basic parts

The Parallax Propeller chip requires a few external components. You need a 3.3-VDC power regulator, a crystal, and a USB-to-serial converter. You also need a serial EEPROM if you want the Propeller to run your program at power up. You can buy all these separately and wire them up on the breadboard. Or you can save time and space with the Parallax PropStick USB. It combines all these external parts on the same footprint as the 40-pin Propeller chip.

I bought the LED display for this project from Mouser Electronics (part number 630-HDSP-521E). The large red segments are common anode (common ground). You supply positive voltage from a propeller port pin through a 220-Ω resistor to light the segments.

I bought the push buttons from Pololu Robotics & Electronics (part number 1400). They are specially designed for mounting on a breadboard. One side of each switch is connected to 3.3 V and the other is connected to a propeller port pin and pulled to ground with a 10-kΩ resistor.

I bought the speaker from Digi-Key (part number 668-1140-ND). The negative terminal of the speaker hooks to the breadboard’s ground. The positive terminal hooks directly to a Propeller port pin.

A speaker, one LED segment, and one switch wired to the Propeller

I placed four of the switches on the corners of the display. These switches are used as up/down inputs for each digit allowing the player to select a number from 00 to 99. The fifth button to the right of the display is the “Enter” button.

The photo above shows the speaker, one LED segment, and one switch wired to the Propeller. I tested the hardware and software incrementally as I hooked it up instead of trying to debug the final system as a whole.

The Parallax Propeller Tool is the free graphical Integrated Development Environment (IDE) you use to develop code for the Propeller. The code editor colors and highlights your work making it easy to see functions and keywords. It also manages indentation. The SPIN programming language uses indentation to identify code blocks much as Python does.

Basic hardware test

The code above is my basic hardware test. The CON (constants) section at the top configures the clock speed of the chip: 5 MHz × 16 = 80 MHz. The OBJ (object) section pulls in the serial terminal driver library. This library object allows you to use the USB cable for both programming and an input/output terminal. The one second pause on line 12 gives you time to switch from the IDE program to the terminal program on your PC once the code is downloaded. The Propeller tool download includes the parallax serial terminal for your PC.

Line 10 sets general I/O pin 0 (P0) as an output (they are inputs by default). Line 17 reads the switch connected to P11 and turns the LED segment on or off accordingly. Line 18 prints the state of the input pins to the PC terminal in an infinite loop.

Parallax serial terminal

It took me a while to warm up to the SPIN programming language. It is syntactically very different from C and its derivatives. But conceptually it is familiar: you break your software up into functions and local/global variables. In the end the simplicity of the syntax and the friendliness of the IDE won me over!

I really like the “Propeller font” used in the Propeller Tool IDE. It includes special symbols you can use to draw circuits and timing diagrams in your code comments. For instance:

Check out the font

Now to wire up the rest of the LEDs and switches. I thought about wiring the left digit to the first port byte and the right digit to the second port byte so that the segments are laid out the same way in each byte. This would make the software easier to write. But the pins for the segments on the display are kind of scattered around at random. The wiring is easier and neater if you wire the segments from the bottom of the display to the bottom of the propeller and from the top of the display to the top of the propeller. You can make up for the scattered pattern with software.

Two tips: Wire the segments from the bottom of the display to the bottom of the Propeller. Wire from the top of the display to the top of the Propeller.

Hi/Lo breadboard layout

That’s it for this installment. Now I’ll clean up all the little wire stripping sprinkles I left around my workbench. In Part 2 of this series, I’ll switch modes from hardware to software and write the Hi/Lo game. Hopefully you are following along. Until next time, may the COGs be ever in your favor.

Chris Cantrell earned an MSEE from the University of Alabama. He writes Java and Flex for Emerson Network Power in Huntsville, Alabama. Circuit Cellar published 10 of his articles between 2002 and 2012: Issue 145, Issue 152, Issue 161, Issue 184, Issue 187, Issue 193, Issue 205, Issue 209, Issue 139, and Issue 260.

User Interface Innovation: Collaborative Navigation in Virtual Search and Rescue

An engineering team from Virginia Tech’s Center of HCI and Department of Computer Science recently won first place in the IEEE’s 2012 3DUI Contest the for their Collaborative Navigation in Virtual Search and Rescue Escort (CARNAGE) project. The project was designed to enable emergency responders to collaborate and safely navigate a dangerous environment such as a disaster area.

The contest was open to researchers, students, and professionals working on 3-D user interface technologies. Entrants were challenged to design an application to enable two users—situated in different locations with his or her own UI—to navigate a 3-D environment without speaking to each other.

Collaborative Augmented Rescue Navigation and Guidance Escort UI (Source: Virginia Tech News, YouTube)

The Virginia Tech team—comprising Felipe Bacim, Eric Ragan, Siroberto, and Cheryl Stinson—described their design in a concise system description, which is currently available on the 3DUI 2012 contest website:

Our task specifically looks at communication between a scene commander and a disaster relief responder during a search and rescue operation. The responders inside the environment have great difficulty navigating because of hazards, reduced visibility, disorientation, and lack of survey knowledge of the environment. Observing the operation from outside of the disaster area, scene commanders work to help coordinate the response effort  [1, 2]. With the responder’s notifications about the environment, scene commanders can provide new instructions, alert the responders to risks, and issue evacuation orders. Since neither the commander nor the responder has complete information about the environment, effective communication is essential.

As technology advances, the incorporation of new tools into search and rescue protocols shows promise for improving  operation efficiency and safety. In this research, we explore the  use of 3D user interfaces to assist collaborative search-and-rescue. Ideally, users should be able to focus on their primary tasks in the VE, rather than struggle with travel and way finding. Using virtual reality (VR) as a prototyping testbed, we implemented a proof-of-concept collaborative guidance system. Preliminary evaluation has demonstrated promising results for efficient rescue operations.

The team also created an explanatory 6:16-minute project video:

Click here for more information about the IEEE Symposium on 3D User Interfaces in Costa Mesa, CA.

Source: Virginia Tech News


FPGA-Based VisualSonic Design Project

The VisualSonic Studio project on display at Design West last week was as innovative as it was fun to watch in operation. The design—which included an Altera DE2-115 FPGA development kit and a Terasic 5-megapixel CMOS Sensor (D5M)—used interactive tokens to control computer-generated music.

at Design West 2012 in San Jose, CA (Photo: Circuit Cellar)

I spoke with Allen Houng, Strategic Marketing Manager for Terasic, about the project developed by students from National Taiwan University. He described the overall design, and let me see the Altera kit and Terasic sensor installation.

A view of the kit and sensor (Photo: Circuit Cellar)

Houng also he also showed me the design in action. To operate the sound system, you simply move the tokens to create the sound effects of your choosing. Below is a video of the project in operation (Source: Terasic’s YouTube channel).

Raspberry Pi: Is It for You?

Unless you’ve been locked in your lab or design studio for the past several weeks, you’ve likely heard about Raspberry Pi, which is a compact, affordable computer that has been creating a buzz on the ‘Net for some time now. The group behind the computer is the Raspberry Pi Foundation, which is a UK-based charity that has an ever-growing following of more than 52,000 followers on Twitter!

(Source: and The Raspberry Pi Foundation)

According to the Raspberry Pi Foundation, “The Raspberry Pi is a credit-card sized computer that plugs into your TV and a keyboard. It’s a capable little PC which can be used for many of the things that your desktop PC does, like spreadsheets, word-processing and games. It also plays high-definition video. We want to see it being used by kids all over the world to learn programming.”

The 85.60 mm × 53.98 mm × 17 mm Raspberry Pi weighs in at 45 g. It features a Broadcom BCM2835, including an ARM1176JZFS and a Videocore 4 GPU.

So, how can Circuit Cellar members use Raspberry Pi? Well, look at it in three ways. One, you can use it in a design of your own. Grab one and start building as soon as you can get your hands on one. Two, you can learn from the “story” of the Raspberry Pi Foundation—how it formed, how it works as a charity—and consider launching a tech foundation of your own. Three, you can design a low-cost embedded design platform or rapid prototyping solution—something distinguishable from the usual suspects of Arduino and mbed—and bring it to market.

In a recent post titled “What Are You Doing!?” at, Tessel Renzenbrink detailed an interview with Eben Upton, a founder and trustee of the Raspberry Pi Foundation. Tessel writes:

Raspberry Pi is grabbing the attention with a $25 computer ($35 for a networked model). In the middle of the storm is Eben Upton. Why is he convinced that a computer which has no casing, no keyboard, no HD and no screen, will be successful? It is time to put the question to him: ‘what are you doing?’

‘We wanted to have a computer especially for Python, and there is a great tradition of naming computers after fruit: like Apricot, Acorn and even today there are computers named after fruit. So Raspberry is following the line of a rich tradition with the Pi, and yes, we wanted this connection with Python. That is where the Pi comes in’, explains Eben when asked for the name Raspberry Pi. And why is it a charity that brings this computer to the market? ‘That all has to do with value creation’, Eben continues. ‘I’ve been involved in several start-ups and then you always end up with the question; how will this create value?’. ‘In this case I do not have to worry about creating value. I can concentrate on designing and producing the board. The Raspberry Pi can be seen as a ‘white label’ product. If there are people out there with a commercial idea for this product, they are more then welcome’.

The Raspberry Pi is a bare PCB board; no keyboard, no HD, no screen.. how will this product become successful? ‘Basically, there is no reason why a computer has to cost more than $50. The peripherals like a screen and keyboard and storage will create a higher price, but with the Raspberry Pi we have taken another route – a normal TV can be used as a screen’, comments Eben. ‘Combine that with a ‘charity shop’ keyboard for a few dollars and you have a full working system’. He further emphazises that ‘the Raspberry is specifically aiming at youngsters learning to program’.

And how about the Raspberry Pi being ‘the next big thing’ after Arduino? There are many hints in that direction on the Internet? ‘The Raspberry Pi is different from the Arduino. The Arduino is great for direct applications and there are dozens of programs available. The Raspberry Pi is a computer system – designed to work with a screen and keyboard, a completely different idea. You can even watch videos with this thing. What might be interesting is the possibility to use the Raspberry Pi as a host for the Arduino board – the combination of these two, resulting in low priced systems can be very interesting and useful’.

‘There is also a difference the flexibility and usability, adds Eben. We have chosen for Broadcom chips and they are not easy to get in the market, making it very difficult to call the Raspberry Pi an ‘open source’ project. We are hoping to take this development into the open source direction, but that will require a new design’.

Can designers use the Raspberry Pi for different applications? ‘Yes, no problem. There is plenty of I/O (I2C and UART) to start using it for whatever challenges you’.

The first batch of 10,000 Pi’s has now arrived from the factory – what will be the next step? ‘Another 10,000 we hope and that is all just the start of it…’

You can read the entire post at

If you want to check out other kits and modules, visit the CC Webshop. is part of the Elektor group.


Robot Design with Microsoft Kinect, RDS 4, & Parallax’s Eddie

Microsoft announced on March 8 the availability of Robotics Developer Studio 4 (RDS 4) software for robotics applications. RDS 4 was designed to work with the Kinect for Windows SDK. To demonstrate the capabilities of RDS 4, the Microsoft robotics team built the Follow Me Robot with a Parallax Eddie robot, laptop running Windows 7, and the Kinect.

In the following short video, Microsoft software developer Harsha Kikkeri demonstrates Follow Me Robot.

Circuit Cellar readers are already experimenting Kinect and developing embedded system to work with it n interesting ways. In an upcoming article about a Kinect-based project, designer Miguel Sanchez describes a interesting Kinect-based 3-D imaging system.

Sanchez writes:

My project started as a simple enterprise that later became a bit more challenging. The idea of capturing the silhouette of an individual standing in front of the Kinect was based on isolating those points that are between two distance thresholds from the camera. As depth image already provides the distance measurement, all the pixels of the subject will be between a range of distances, while other objects in the scene will be outside of this small range. But I wanted to have just the contour line of a person and not all the pixels that belong to that person’s body. OpenCV is a powerful computer vision library. I used it for my project because of function blobs. This function extracts the contour of the different isolated objects of a scene. As my image would only contain one object—the person standing in front of the camera—function blobs would return the exact list of coordinates of the contour of the person, which was what I needed. Please note that this function is a heavy image processing made easy for the user. It provides not just one, but a list of all the different objects that have been detected in the image. It can also specify is holes inside a blob are permitted. It can also specify the minimum and maximum areas of detected blobs. But for my project, I am only interested in detecting the biggest blob returned, which will be the one with index zero, as they are stored in decreasing order of blob area in the array returned by the blobs function.

Though it is not a fault of blobs function, I quickly realized that I was getting more detail than I needed and that there was a bit of noise in the edges of the contour. Filtering out on a bit map can be easily accomplished with a blur function, but smoothing out a contour did not sound so obvious to me.

A contour line can be simplified by removing certain points. A clever algorithm can do this by removing those points that are close enough to the overall contour line. One of these algorithms is the Douglas-Peucker recursive contour simplification algorithm. The algorithm starts with the two endpoints and it accepts one point in between whose orthogonal distance from the line connecting the two first points is larger than a given threshold. Only the point with the largest distance is selected (or none if the threshold is not met). The process is repeated recursively, as new points are added, to create the list of accepted points (those that are contributing the most to the general contour given a user-provided threshold). The larger the threshold, the rougher the resulting contour will be.

By simplifying a contour, now human silhouettes look better and noise is gone, but they look a bit synthetic. The last step I did was to perform a cubic-spline interpolation so contour becomes a set of curves between the different original points of the simplified contour. It seems a bit twisted to simplify first to later add back more points because of the spline interpolation, but this way it creates a more visually pleasant and curvy result, which was my goal.


(Source: Miguel Sanchez)
(Source: Miguel Sanchez)

The nearby images show aspects of the process Sanchez describes in his article, where an offset between the human figure and the drawn silhouette is apparent.

The entire article is slated to appear in the June or July edition of Circuit Cellar.