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Dave Doherty Executive Vice President of Operations for Digi-Key

Key Success


Digi-Key’s Dave Doherty on how the company’s hybrid model has changed component distribution

Makerbot 3D Scanner Overview Sneak Peak at Johnson Space Center

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Featured Products

This week’s latest products from EEWeb.

MakerBot's Digitizer 3D Scanner

With MakerBot's new desktop scanner, they bring 3D innovation to the masses.

Speed2Design at NASA's Johnson Space Center

The second part of the Speed2Design contest brought 10 lucky contestants to the historic Johnson Space Center.

Dave Doherty

Executive VP of Operations for Digi-Key

18 10

A conversation about how Digi-Key's hybrid model has changed component distribution.

Designing With GPS

A look at some surprising new applications of global positioning systems.

Open Source Galileo & Raspberry Pi Boards



A comparative look at the pros and cons of these wildly popular open source boards.

A "printf" for FPGAs

A look at how to put a printf in your code to avoid daunting tasks and to get straight to the source of the problem.


Return to Zero Comic


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PULSE 4-bit Asynchronous Bus Arbiter The 74F786 is an asynchronous 4-bit arbiter designed for high speed real?time applications. The priority of arbitration is determined on a firstcome first-served basis. Separate bus grant (BGn) outputs are available to indicate which one of the request inputs is served by the arbitration logic. All BGn outputs are enabled by a common enable (EN) pin. In order to generate a bus request signal a separate 4 input AND gate is provided which may also be used as an independent AND gate. Unused bus request (BR) inputs may be disabled by tying them high...Read More

Low Voltage Output Comparator The NCX2222 provides a dual, low voltage, low-power comparator with open-drain outputs. The NCX2222 has a very low supply current of 5 μA per comparator and is guaranteed to operate at a low voltage of 1.3 V. It is fully operational up to 5.5 V which makes it convenient for use in both 3.0 V and 5.0 V systems. The NCX2222 also has a wide supply voltage range from 1.3V to 5.5 V with rail-to-rail input/output performance and a very low supply current of 5 μA per comparator...Read More

Li-Ion Battery Switching Charger IC R2A20057BM is a semiconductor integrated circuit designed for Lithium-ion battery charger control IC. Built-in Input current limitation circuit compliant with USB requirements and dual output (system and battery) control circuit allows to supply the system power and the battery charging power simultaneously from input power. The IC allows USB charging with a high precision charge control voltage. It has auto load current distribution control and is compliant with the JEITA guideline...Read More

Switched Capacitor Lowpass Filters The MAX7418–MAX7425 5th-order, low-pass, switched-capacitor filters (SCFs) operate from a single +5V (MAX7418–MAX7421) or +3V (MAX7422– MAX7425) supply. These devices draw only 3mA of supply current and allow corner frequencies from 1Hz to 45kHz, making them ideal for low-power post-DAC filtering and anti-aliasing applications. They feature a shutdown mode that reduces supply current to 0.2µA. Two clocking options are available: self-clocking (through the use of an external capacitor), or external clocking for tighter corner-frequency control...Read More



FEATURED PRODUCTS Half Bridge Driver Evaluation Board The EVBD4400 evaluation board implements a single power phaseleg circuit on double sided PCB with ground plane, using the proven ISOMART HALF BRIDGE DRIVER CHIPSET – IXBD4410, IXBD4411, IXDP630. The IXDP631 is optional. This board includes all parts required for the circuit implementation so that you can just follow the instructions in this document and connect the board to the load and power. The kit consists of an assembled and tested PCB with two power devices...Read More

High-performance Embedded Arrays Fujitsu’s CE71 is a series of high-performance, 0.18µm Leff CMOS embedded arrays that include full support of diffused high-speed RAMs, ROMs, mixedsignal macros, and a variety of other embedded functions. The CE71 series offers density and performance similar to those of standard cells, yet provides the time-to-market advantage of gate arrays. The CE71 series devices include 44µm, 66µm, or 88µm pad pitch for a cost-effective solution for both pad-limited and core-limited designs...Read More

Accurate RGB Digital Light Sensor Intersil Corporation announced the ISL29125 digital light sensor, the industry’s most accurate, lowest power and smallest Red, Green and Blue (RGB) sensor that optimizes the display resolution and color quality of mobile devices and TVs in all lighting environments. The ISL29125 RGB sensor communicates directly with a device’s core processor to enable the automatic adjustment of display brightness based on changing light conditions, providing consumers with a more crisp and color consistent experience while extending battery life...Read More

600V to 1.7kV IGBT Driver Core The 1SD1548AI IGBT driver is based on CONCEPT’s highly approved SCALE-1 chip set that was developed specifically to enable IGBTs to be reliably-driven and safely operated. The driver features a high gate current of ±48 A and a high power output of 15 W. It has been specially developed for highfrequency applications (e.g. resonant converters) with a high gate power requirement or for high gate-current driving applications (e.g. parallel connection of high-power IGBT modules). The driver features electrical isolation between the control electronics and the power section...Read More



PULSE RF Signal Chain Portfolio IDT announced the expansion of its industry-leading RF signal chain portfolio with a high-performance digital pre-distortion (DPD) demodulator. The new integrated DPD demodulator improves system performance while reducing solution cost, physical size and power consumption in 4G, 3G, and 2G wireless base stations and repeaters. The IDTF1320 and IDTF1370 are high-performance, low-power DPD demodulators optimized for 400 MHz to 1200 MHz and 1300 MHz to 2900 MHz wireless systems, respectively...Read More

Highly Integrated Power Monitoring IC Microchip Technology announced a new power monitoring IC, the MCP39F501. This device is a highly integrated, single-phase power-monitoring IC designed for realtime measurement of AC power. It includes two 24-bit delta-sigma ADCs, a 16-bit calculation engine, EEPROM and a flexible two-wire interface. An integrated low-drift voltage reference in addition to 94.5 dB of SINAD performance on each measurement channel allows accurate designs with just 0.1 % error across a 4000:1 dynamic range. The MCP39F501 power monitoring IC allows designers to add power monitoring to their applications with minimal firmware development...Read More

Color Light-to-Digital Converter The TCS3471 family of devices provides red, green, blue and clear light sensing (RGBC) that detects light intensity under a variety of lighting conditions and through a variety of attenuation materials. An internal state machine provides the ability to put device into a low power mode in between RGBC measurements providing very low average power consumption. The TCS3471 is directly useful in lighting conditions containing minimal IR content such as LED RGB backlight control, reflected LED color sampler, or fluorescent light color temperature detector...Read More

LIN System Basis IC The new MLX80050 from Melexis extends its successful LIN transceiver and system basis product line for the simple and effective development of LIN slaves. This IC combines a physical layer LIN transceiver according to LIN 2.x as well as SAEJ2602 with a 5 V voltage regulator with RESET output for the connected microcontroller. This IC is optimized in accordance with the increased EMC requirements for single wire bus systems as well as the “Hardware Requirements for LIN, CAN and Flexray Interfaces in Automotive Applications� defined from German OEMs...Read More

Audio DSP with 2-Channel SRC The AK7736B is a highly integrated audio digital signal processor with integrated 2ch SRC. It includes internal memories for digital audio processing, that allows surround effect process, time alignment and parametric equalizing. Moreover, the AK7736B can process both data and filter coefficients as floating point data so that high accuracy IIR/FIR filter performance can be achieved easily. The AK7736B can operate a hands-free software by AKM as well as sound processing, by programs downloaded via the microprocessor interface...Read More



FEATURED PRODUCTS High Precision Hall Effect Sensor The A1356 device is a high precision, programmable open drain Hall-effect linear sensor IC with a pulse width modulated (PWM) output. The duty cycle (D) of the PWM output signal is proportional to an applied magnetic field. The A1356 device converts an analog signal from its internal Hall element to a digitally encoded PWM output signal. The coupled noise immunity of the digitally encoded PWM output is far superior to the noise immunity of an analog output signal. The dynamic offset cancellation circuits reduce the residual offset voltage of the Hall element...Read More

UV Sensor Based on SoI Technology LAPIS Semiconductor has developed the ML8511 UV Sensor to detect ultra violet rays with Si (silicon) device using the original SOI (Silicon on Insulator) technology. The ML8511 measures the amount of ultra violet rays contained in the sunlight, and it is used for various equipment that display the suntan by ultra violet rays, the guidance for UV care of skin, etc. The ML8511 is ideal for mobile computing devices, such as smart phones, mobile phones, and watches, at low power and in a compact package (QFN)...Read More

Low Power Digital Audio Interface The EP7309 is designed for ultra-low-power applications such as digital music players, Internet appliances, smart cellular phones or any handheld device that features the added capability of digital audio decompression. The core-logic functionality of the device is built around an ARM720T processor with 8 KB of four-way, set-associative unified cache and a write buffer. Incorporated into the ARM720T is an enhanced memory management unit (MMU), which allows for support of sophisticated operating systems like Microsoft速 Windows CE速 and Linux速. The EP7309 is designed for ultra-low-power operation...Read More

Highly Reliable DC-DC Converters Murata announced the SPM series of low power isolated DC-DC modules designed specifically for use in electronic equipment that will be subject to harsh environments such as outdoor communications, applications with little or no forced air cooling, smart grid and industrial process control equipment. The SPM15 series is designed for applications that require Vin ranges of 9-36V or 18-75V at 15W. The SPM25 series covers applications that require Vin = 36-75V at 25W. The SPM15 & SPM25 series provides single output voltages of 3.3, 5 or 12 VDC..Read More



FEATURED PRODUCTS 400 Watt Series for Medical & Industrial Astrodyne Corporation is excited to give you a sneak peek of what’s coming out in the First Quarter for 2014! Astrodyne would like to introduce the ASM400 Series for Medical and Industrial market. The ASM400 series has a compact, high density design with a whopping 19W/in3 in an open frame 3×5 inch form factor (400W @ 250LFM, 40°C, 250W with natural convection, 40°C). The series is less than 1U high -1.4in. It is designed to meet EN60601-1 3rd edition and has a Class 2 option for home use...Read More

Quick-Start Wireless Solutions Digi-Key has announced a global distribution agreement with Bluegiga Technologies, a market innovator in the wireless space. The company manufactures highly integrated wireless modules employing the latest wireless technologies, including Wi-Fi, Bluetooth, and Bluetooth Low Energy. Finland-based Bluegiga provides innovative, easy-to-use, short-range wireless connectivity solutions to OEMs, device manufacturers, and system integrators. The company is well known for their Bluetooth solutions, and their unique module firmware provides a simple interface for configuration of the devices for specific design implementation...Read More

Silicon Elastomer for Advanced Applications Master Bond MasterSil 801 is a room temperature curing, silicone for high performance bonding and sealing. It features a paste consistency and a non-corrosive cure. With serviceability up to 300°C, this one part system offers unsurpassed stability at elevated temperatures. Master Bond MasterSil 801 is a one component, high performance silicone elastomer compound for bonding, sealing, coating and formed-in-place gaskets. This specialty system features a combination of exceptionally high temperature resistance, flexibility and non-corrosive cure...Read More

Power Inductors for High Temperature Coilcraft CPS announces its new AE619PYA Series of high-temperature, military-grade power inductors that meet all NASA low outgassing specifications. These robust, composite-core surface mount inductors are constructed of high-temperature materials to exceed the requirements of most military and aerospace applications, such as driver circuitry, DC-DC converters, switching power supplies, power inverters, and filters. Soft saturation makes them ideal for voltage regulator module (VRM/VRD) applications. The AE619PYA Series offers a full-rated temperature range of -55° to +115°, and operation to 155°C with current de-rating...Read More



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DIGITIZER Delivers 3D Innovation for the Masses




Since 2009, MakerBot has been supplying hackers of 3D space the sophisticated tools necessary for transporting the bits and bytes of the digital realm into the physical world. Their latest announcement of the MakerBot Digitizer Desktop 3D Scanner however completes the cycle. By facilitating the return of physical objects to their digitized form, MakerBot has inextricably linked these otherwise disconnected worlds once and for all.




Introducing the

MakerBot Digitizer



The 3D printing revolution is here. With rapidly declining costs, it won’t be long before 3D printers become furniture in everyone’s home. But as the means for creating objects becomes more affordable and accessible, the digital building blocks needed to generate 3D content continues to be limited to those skilled enough to develop 3D designs from scratch. As Jenifer Howard, Director of Public Relations at MakerBot told EEWeb, “For the many who 3D print, there’s been a barrier for 3D printing if you didn’t know design software or had design capabilities." Previously, if you wanted to 3D print, there were three ways to do so; you could go to a website and download a design that someone else has created, you could create something



on your own using CAD software and create an STL file that can then be printed, or you could scan something. The MakerBot Digitizer Desktop Scanner removes the obstacles facing aspiring creators. By placing 3D design and printing at the consumer level for the first time, everyone from the homeschooler to the hacker will have the means to create 3D printable designs. “We wanted to create a scanner that was really compatible with our Desktop 3D printers," Howard said, referring to the Digitzer. "We look at it as kind of a washer/dryer combination— it makes the design process so much easier when you no longer have to be a designer to create something that you can then print in 3D." For those who are good at designing, the Digitzer provides a good jumping off point for those who need inspiration. As with all MakerBot products, the MakerBot Digitizer Desktop Scanner is designed for maximum ease of use. It has a wonderful user interface that makes 3D printing really easy. The MakerBot team created MakerWare for the 3D Digitizer. Users can just go

"We wanted to that was really c Desktop 3


to and download it for the Digitizer. It's a simple software program that guides users of all skill levels through the process. The Makerware software works in tandem with Mac, Windows, and Linux operating systems. Technical Specifications Unlike traditional 3D scanners – large and ex-

pensive devices utilized in predominately industrial settings—the MakerBot Digitizer Desktop Scanner weighs in at just four and a half pounds. As Jenifer explained, “The overall Digitizer itself is pretty lightweight. If you want to use it in your office and then take it home for the weekend and be scanning, it’s very easy. That was a big point in creating it for our market—we make desktop 3D printers and people like to move

o create a scanner compatible with our 3D printers."




their desktop 3D printers and sometimes they like to take them home or to work or to events. We wanted the Digitizer to be on that same level.� Getting the MakerBot Digitizer Desktop Scanner up and running only requires a computer, a USB cable, and an outlet. The turntable stepper motor indexes 800 steps during a full rotational scan. The two eyesafe class lasers can track and scan objects ranging from 2 inches to 8 inches tall and wide. Throughout the entire 3D rendering process, the scan lines produced by the lasers are captured by an embedded digital camera, resulting in a near replica of the original object in about 12 minutes. “It creates about 200,000 triangles per 3D model, which are then formed in the STL file. The digital resolu-

Click above to watch a video overview of the MakerBot Digitizer




"The MakerBot Digitizer Desktop Scanner can create a near-perfect 3D image of just about any physical object within the given size requirements." tion is about 0.5 millimeters, so it’s fairly good. It also has a dimensional accuracy of about 2 millimeters,” Howard added. Details less than 0.5 millimeters are interpolated by the MakerWare software resulting in a water-tight image with no additional cleanup required. Light, matte objects like ceramics, clays, and non-glossy plastics produce the best scans. But with a little glare-reducing baby powder, the MakerBot Digitizer Desktop Scanner can create a near-perfect 3D image of just about any physical object within the given size requirements. Applications There appears to be no end to the potential created by the affordable and efficient 3D scanning made possible by the MakerBot digitizer. Applications range from Architecture, Education, Engineering, robotics, the creative arts, to just having fun. “We’ve been scanning all sorts of different items here in the office," Howard told us, "Our CEO’s assistant went on her honeymoon and she came back with this beautiful

conch shell. We’ve been having so much fun scanning it and you can actually see all of the bumps and ridges that are in the conch shell." The MakerBot team has also been seeing a lot of architects embracing the technology—as well as doing creative projects that need that jumping off point. "We have a lot of educators at schools who are customers of ours," Howard stated, "the schools are really loving the Digitizer because they have students that don’t have those design capabilities who are now able to create something immediately and print it and see those results in a really short time period." Museums are also hopping on board. Howard stated that the team had quite a few orders from museums that are going to be scanning collections and then print them and make their collections accessible for educational programs—even programs for the blind. A museum in Europe plans on using the Digitzer to scan items for an exhibit for people that were vision impaired so that they can actually feel what they were experiencing. Start Innovating The MakerBot Digitizer can be ordered directly from the MakerBot website. At $949 plus an additional $150 for the MakerCare service plan, the MakerBot Digitizer is priced at the consumer level. By removing the time consuming 3D design process, MakerBot has made it easier than ever to manipulate 3D space and has truly placed 3D innovation in the hands of the masses.



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at NASA's Johnson Space Center



FEATURED ARTICLE Alex Maddalena Editor at EEWeb

Earlier last month, Littelfuse, a global leader in circuit protection products, teamed up with NASA for the biannual Speed2Design event. Whereas the first event took place at the NASA Ames Research Facility in the heart of Silicon Valley, Speed2Design decided to harken back to NASA’s roots by hosting the following event at the historic Johnson Space Center in Houston, Texas. Established in 1961 as NASA’s Manned Spacecraft Center, Johnson Space Center continues today as the primary command center for human space exploration. From the legendary early space missions Gemini and Apollo, to the ongoing construction of the International Space Station, Johnson Space Center remains a hotbed of activity as NASA scientists team up directly with astronauts to address all aspects of supporting space exploration. EEWeb was invited to the event alongside 10 lucky winners of the Speed2Design program. Not only were we able to see some astonishing new technology for future space missions, but were also given a closeup look at some of the most important technological achievements in human history.



PULSE The One and Only Mission Control You’ve seen it in the movies; rows of computer monitors, buttons, switches, and telephones— all facing a wall-sized monitor showing astronauts floating in real-time. A few dozen men and women with headsets sit behind the screens, eyes glued to the mission unfolding in front of their eyes. This, of course, is Mission Control—perhaps the most historic room in the country, next to the Oval Office. It was in this room where the NASA crew aided the members of the Apollo 13 mission back to safety, where they witnessed the tragic end to the Challenger Shuttle, and where NASA— and the world—watched man’s first walk on the moon. To say there is history in this room is an understatement. Walking into the Christopher C. Kraft, Jr. Mission Control Center is a surreal experience. Typically depicted in the tensest moments of blockbuster movies, it was fascinating to see Mission Control going through daily operations (and without background music). The main wall monitors show a map of the globe with a live tracker of the International Space Station’s orbit, live views of the interior and exterior of the ISS, as well as other vital statistics. While there is always a need for communication with the astronauts on board the ISS, only 10% of mission controllers’ time is spent controlling shuttle missions. 15% of the time is spent with mission training, and the remaining 75% is spent on planning and organizing future missions.

The International Space Station travels at 17,227 miles per hour and completes roughly 15 orbits per day. 20


Showing the view of Earth from the ISS gave us a glimpse at some of the potential applications and data it can monitor. Being that the ISS is the only laboratory in outer space, it is guaranteed that at any given time there are experiments going on geared towards improving life on Earth. From biochemistry experiments on the effects of aging in humans to studies in technology to monitor droughts in the Midwest, the range of experimentation affects all facets of everyday life. In fact, just recently, the Obama Administration vowed to extend the life of the ISS until at least 2024, allowing for further exploration and experimentation, as well as a continued American presence in outer space.

FEATURED ARTICLE Robonaut: A Dexterous Humanoid Robot The next part of the tour brought the group to the Robotic Systems Technology branch at NASA, which is responsible for the Robonaut. The Robonaut is a dexterous humanoid robot that is designed to aid—not replace— astronauts in orbit. Although the Robonaut is modeled after the human body, it can do things that the human body cannot. For instance, the Robonaut’s arms can move with 7 degrees of freedom and can lift a significant amount of weight for up to 15 minutes. This aspect is extremely beneficial for missions that require potentially dangerous tasks outside of the ISS. The current Robonaut is primarily a torso that can be attached to parts of the ISS for specific tasks, but it will eventually have legs that can latch on to handrails on both the interior and exterior of its environment for independent movement. One of the most astonishing features of the Robonaut is its ability to locate an independent object and pick it up with its robotic hands. The robotics team did a demonstration of this ability by simply placing an electric drill on a table in front of the Robonaut. What followed next was amazing; the Robonaut, recognizing the object in front of him, moved his head in the direction of the drill, extended his arm towards it, wrapped his fingers around it, and pressed on the trigger of the drill to use it. The dexterity of the fingers mimicked the exact movements of a human being’s. The Robonaut is able to do this by recognizing the standalone object, digitally painting that object green (if it thinks it can pick it up), and creates a map of how tall the object is, and how far the arm needs to extend in order to pick it up. Although this may seem like too lengthy a procedure just to pick up an ordinary object, you have to take yourself out of gravity’s orbit to see it’s benefits; when an astronaut is floating in the ISS making critical repairs, he or she needs to have a reliant way of obtaining the necessary tools without having to break the focus from the objective. That’s where the Robonaut comes in. While there is still a ways to go to get the response time and mobility to advance, the Robonaut is definitely one of the most capable, independent robot humanoids out there today. Visit:



Above: The NBL's 6.2-million-gallon pool Right: Saturn V Rocket Everything is Bigger in Texas After seeing the Mission Control Center, and some amazing robotics technology, the scale of the tour increased tenfold. The group was brought into the Neutral Buoyancy Laboratory (NBL) at the Sonny Carter Training Facility just outside of the NASA campus. The term neutral buoyancy refers to something that has equal tendency to float as it does sink, much like the conditions in zero gravity. To simulate these conditions here on Earth, NASA built a huge facility that houses a 40-feet deep pool that contains 6.2 million (yes, million) gallons of water. The sheer size of this pool allows for astronauts to train—in their space suits—for zero gravity missions on the ISS. Submerged in the pool is an exact replica of a section of the ISS—even at its immense size, the NBL pool is not large enough to house an entire replica. The astronauts are still able to familiarize themselves with the external layout and conditions they will face when in orbit.



After seeing the NBL pool, the group was brought to the Saturn V Facility in Rocket Park. Inside this enormous warehouse is the Saturn V rocket used to send people to the moon. At 363 feet in length, the Saturn V is around the height of a 36-story building. Although the rocket is the size of a large building, the only part that makes it into orbit is a (relatively) small module at the very top. The remaining large capsules are filled completely with fuel—released in critical launch stages—to propel the rocket into space. The fact that this immense machine can be launched at 17,000+ mph through the Earth’s atmosphere really makes you marvel at how far mankind has come in terms of technology. The already unforgettable day was capped by an unforgettable evening when the group was able to meet legendary astronaut, David Leestma. In his lengthy career at NASA, Leestma has been on three space flights and logged over 500 hours in space, and has





countless stories and recollections from his time in orbit. To hear his first-hand account of the day of his first launch, his first view of planet Earth from space, and to see his own photography while onboard the ISS was probably the standout moment of the day. Leestma spoke with passion and emotion about his experiences in space that most people on Earth will never get to experience for themselves. It was yet another successful Speed2Design event from Littelfuse. Selecting NASA’s facilities for the contest really heightened the awareness of our reliance on technology and engineering. Every aspect of technological advancement that mankind has made in the past century has been reliant on technology in some way. NASA in particular has been not only dependent on, but also active in the development of new technologies to electronic devices that enable us to explore some of the biggest questions that face



humanity. The circuit protection products that Littelfuse offers allow for these technological feats to remain stable and secure—especially in these critical applications where the livelihoods of astronauts are at stake. To view more photos and videos of NASA, visit: To learn more about Littelfuse and the Speed2Design programs, click the images below:

Join Today


Key Success to



Dave Doherty

Executive Vice President of Operations


Digi-Key is a leading global supplier of electronics components. Founded in 1972, Digi-Key had humble beginnings as a small components supplier in Thief River Falls, Minnesota. Since then, the company has had explosive growth, with over 2,600 employees joining the team, upwards of 3 million orders shipped per year, and an ever-expanding global presence. The company's success is often attributed to their focus on superior customer service, which has been a touchstone of the company since day one. EEWeb's Cody Miller recently spoke with Dave Doherty, Executive Vice President of Operations for Digi-Key, to learn more about the keys to the company's success and how the company plans on maintaining their status at the top.




"As our business continues to evolve in response to changing customer expectations and needs, we will remain 100-percent committed to offering a centralized team of technical resources, tools and knowledge."

Can you give me a little background about yourself? Currently, my role at Digi-Key is to lead the operations side of our constantly changing global business. This includes leading product fulfillment and distribution, marketing, application engineering, e-commerce, technical support, purchasing, and several other functional areas. After six years with the company, each day I’m both challenged and impressed with our team and our ability to continue to scale our business and respond to changing customer needs. Prior to joining Digi-Key, I spent 13 years at Arrow Electronics where I held various positions in sales, business development and marketing. Prior to that, I worked in manufacturing industry with Digital Equipment in developing their VAX product. All in all, my industry experience spans 30 years with a mix of time in manufacturing, sales, and other customer-facing positions in component distribution. I earned an Electrical Engineering degree from Worcester Polytechnic Institute and an MBA



from Babson College. Last but not least, as a Boston native I must add that I am, of course, a huge fan of Red Sox baseball and Bruins hockey.

There have been a lot of discussions about Digi-Key’s Prototype to Production® model and unique approach to distribution. Can you talk about this concept? Digi-Key coined the term “Prototype to Production” to best describe our distribution model which spans the needs of the design engineer throughout the entire product design-to-production process. What’s unique about this ‘hybrid’ model is that it combines the attributes of a high-service ecommerce provider with personalized production-level supply chain capabilities offered by traditional broad line distributors. The model naturally evolved from our understanding on how to serve engineers seeking easy access to design tools, educational materials and multimedia resources to support product innovation.

INTERVIEW We learned that professional engineers and purchasers alike seek speed, efficiency, and a simpler way to select and buy parts – from a single part to higher volume production run quantities. As a result, we chose to expand our tools and resources available to support the entire lifecycle of a product. Many of our core strengths lend themselves well to the needs of the next generation engineer and/or purchaser seeking new ways to collaborate with a distributor like Digi-Key. Most importantly is Digi-Key’s commitment to offer the broadest selection of electronic components in the industry, available for rapid delivery anywhere in the world. We make it easy for customers to source leadingedge products, on their schedule, in their preferred quantity – from a single part to tens of thousands of parts. In addition to product selection, we understand how important timing is to our customers. Despite our contemporary model, Digi-Key is still a little stubbornly old-fashioned in how we handle inventory. By breaking some of the text book rules of supply chain management, we are able to stand out from the pack. At the core of our business success is our decision to stock product onsite versus relying upon complex supply chain techniques. We will continue to hold strong to our commitment to alleviate inventory risk for our customers by housing over one million parts at our globally central facility in Thief River Falls, Minnesota.

How does this model align with the changing needs of the "next generation" engineer and how does this compare with the needs and buying habits of the component purchaser? We know that professional engineers are always on the search for the latest and greatest technology components so that can stay ahead of the innovation curve and speed time to market. By focusing on a wider spectrum of services, Digi-Key’s Prototype to Production model allows us to serve customers from design to launch to full-scale production– all with ultra-efficiency and speed. We are seeing more and more productionlevel customers around the world turn to Digi-Key so that they can access the widest BOM coverage in the industry supported by a full suite of supply chain services. In

fact, we’ve been able to eliminate and/or reduce the carrying costs associated with the sourcing process, allowing companies to run faster and leaner. The success of our model is built upon our promise to support the needs of the design engineer, which we understand intimately after over 40 years in the business. Today, we’ve simply scaled our business to support a broader range of global customers which represent businesses of all sizes. The common denominator, however, is that all of our customers, engineers and purchasers alike– have come to expect a fast and easy buying experience from Digi-Key. As our business continues to evolve in response to changing customer expectations and needs, we will remain 100-percent committed to offering a centralized team of technical resources, tools and knowledge. By providing fast and easy access to technical content and on-demand resources, multiple touch points, immediate answers and excellent service, Digi-Key continues to build its fan base. Our customers keep coming back to access the broadest selection of parts available for immediate delivery which, in turn, supports the entire product lifecycle from prototype to production.

Recently, I was on a couple of tours of assembly houses, local US assembly facilities, and contract manufacturers and they all said they had a close relationship with Digi-Key. I think the reason most of them suggested that they work so close with you is because you have everything they need and you were able to provide it very quickly. This is absolutely true. We cherish these relationships and, they go hand in hand with the ultimate benefits of our model. Customer relationships such as these actually start one level upstream from quick-turn assembly houses, beginning with the engineers themselves. It is a tremendous point of pride and validation for our business when suppliers and engineers relate the availability of a new product directly to Digi-Key. Many tell us that if it is not in stock at Digi-Key, then it is not real. In most cases, engineers will start their relationship with Digi-Key by searching for Visit:


PULSE components, building a bills of materials and sourcing them from us to design and test prototypes. Then, when they get to their quick-turn assembly partners, it is a natural progression for them to come back to us and place a production order. Since they sourced the parts from us initially, there is a high probability that we stock the correct parts. Besides confidence in part availability, assembly partners need a solid relationship with a dependable distributor who can react quickly to support a grueling production schedule as many build thousands of assemblies over the course of the year.

When it comes to service, many big distributors will have boots on the ground, but your company still provides a high level of service without having regional sales representatives. What are some of the available services within the company that engineers take advantage of?

"Our business model is designed around responding to a customer’s specific parts order–ranging from a single component to a more complex, high-mix, low-volume, productionlevel order." 30


To provide some background, I started my career as an application engineer and later migrated into technical sales. Customers often desired regular face time with a sales person to discuss product road maps and/or development schedules. Many of my activities consisted of dropping off a datebook or sharing my own design experiences, guiding them in the selection of complementary components. I consumed many hours of “windshield” time, struggling with time management in maintaining a satisfactory level of visibility to support those key customers. In contrast, today the internet has dramatically changed customer behavior and how they access information on demand, in real time and/or interact with businesses and industry experts. As technology advances and we see an increasing prevalence of mobile applications, social engagement and self-service capabilities, it’s clearly a different world that it was just 10 years ago. The vastness of the available content and a shift toward specialization makes it very difficult to serve customers in the field with the right level of resources. It’s inevitable that customers have turned to centralized technical support centers along with searchable repositories of online,

INTERVIEW multimedia content and other resources. The benefit again comes to speed, efficiency and the ability to access relevant, timely resources, on demand. Today, customers cannot afford to wait for a travelling field representative to visit their area. Instead, they require easy access to real world answers, specialized and searchable resources, on demand content in multiple formats and, of course, a fast and easy connection to a live person. As a testament to the reality of this trend, DigiKey averages over 1,400 technical inquiries a day–1,100 or so by phone and 300 to 400 through technical web chats. In response, we have over 150 technical resources centralized at our headquarters–available 24 x 7. Our technical team consistently responds to incoming requests, literally within seconds. Knowledgeable technicians including specialized application engineers, guide customers through the selection and design process by discussing part comparisons, sharing examples and solving problems. We also have a team of 400+ dedicated multi-lingual customer service professionals, available 24 hours a day, 365 days a year. As opposed to more traditional distributors, we measure service levels not in visits per week but response time and customer satisfaction. Today’s global buyers have come to expect immediate access to knowledgeable technical support and customer service resources and these kinds of demands for speed and access are only increasing. In response, at Digi-Key we will continually build upon and continually improve our model and we align our resoruces with a shift in how customers prefer to interact with our business.

Can you elaborate a little bit on the process of how Digi-Key fills orders so quickly? Some of our competitors are 3PL expert or specialized in MRO and replacement parts. They operate very efficiently, serving complex supply-chain requirements with state-of-theart forecasting and replenishment tools. These companies are experts in terms such as return on working capital, and their products are typically shipped only in manufacturer pack quantities.

In comparison, Digi-Key’s model is fundamentally different from these kinds of distributors and the others. Our business model is designed around responding to a customer’s specific parts order – ranging from a single component to a more complex, high-mix, low-volume production-level order. Digi-Key will pick and pack any quantity of parts – typically shipping the order anywhere in the world within the same day the order was placed. For our production business customers, one unique value-add service is our “Digi-Reel” offering which is a custom reel based on specified part quantities. We’re seeing a growing need for these types of personalized services to save customers time and cost. Although advanced technology around surface mounting has made it easier to insert board-level products by hand, they still require a high-end pick-and-place machine. With a “Digi-Reel”, however, we will create a custom tape and reel, complete with leader and trailer. As a result, customers are able to eliminate a great deal of waste, save space and increase their overall efficiency while speeding time to market. At its core, the Digi-Key model shares some common elements with traditional distributors in serving the varying demands of production customers, engineers, hobbyists, and students. The difference comes down to our excellence in delivering high-mix, lower volume production orders. This level of sophisticated customization, dedicated resources and high-service, can alleviate significant inventory risk and slashes costs for the end-customer. By starting with the engineer, either by assisting with a discrete design or via an EDA/CAD tool interface, Digi-Key is uniquely able to partner with today’s global electronic component buyer to support their sourcing needs for internal prototypes, small production builds or higher volume outsourced manufacturing runs.

Can you give a brief history about the company? The company was actually started in 1972 by a local businessman and company founder, Ron Stordahl, who has a Ph.D. in Electrical Engineering. Dr. Stordahl initially developed a digital keyer for ham radio enthusiasts Visit:


PULSE using a variety of solid state components. As a devoted hobbyist, he was frustrated in that he had to source full order quantities of parts from component manufacturers. After doing some research, he identified a significant market opportunity in offering smaller quantities of electronic components to engineering enthusiasts. Soon, Stordahl began sourcing products and advertising them to hobbyists, students, and budding engineers like himself. After the company’s initial success, Stordahl’s childhood friend Mark Larson joined the company in 1976. Larson provided business leadership for the company, maintaining a consistent brand promise centered on listening to customers and responding to their needs. Today, Digi-Key is located in the small town of Thief River Falls in Northwest Minnesota, which is home to both Stordahl and Larson. The entire community of 8,500 residents

"Digi-Key ships to over 180 countries, offering localized websites in 10 languages and 15 currencies. We’ve learned that in a fastpaced global economy, customers care less about your physical location and more about the value of services provided."



along with the surrounding rural area continues to play a large role in Digi-Key’s success while offer a unique setting for the company’s 2,600 employees who work out of the company’s headquarters.

It is fascinating that you are in a remote part of Minnesota, yet Digi-Key is truly a global business with customers worldwide. Can you elaborate on the worldwide presence of Digi-Key and how you export products? We credit the power of the Internet to enabling our rapid growth and expanding worldwide presence. Initially, we reached customers by sending out a large product catalog, which as the industry standard at the time. In 2010, however, Digi-Key was one of the earliest and most aggressive adopters of ecommerce. There was a low barrier to migrate from a catalog to the web, and, despite some inevitable resistance from our customer base the tremendous advantages quickly became apparent. Today, with a focus on high-value content, search engine optimization, web analytics, we make it very easy for customers to find the right products for their projects. Digi-Key ships to over 180 countries, offering localized websites in 10 languages and 15 currencies. We’ve learned that in a fastpaced global economy, customers care less about your physical location and more about the value of services provided. Most of our customers today, in fact, are not looking for a single component. Rather, they are sourcing an entire bill of materials which requires an even higher level of localized and searchable content and resources. In turn, we’re focused on leveraging the power of the web to give our customers the best possible user experience. I believe that Digi-Key is in the best possible position to meet the needs of our constantly growing and evolving customer base, part, through our partnerships with top industry suppliers and by our unwavering commitment to the customer. You’ll continue to see vast, deep and high-value content and resources that enable innovation around technology applications from semiconductors to passives to connectors and electromechanical components. The possibilities are limitless.

INTERVIEW What are some of the things that you might be able to tell the client or customer about the reasons and the value of getting Digi-Key’s service? What are some of the other concerns that would help the client or customer? Digi-Key has always put the customer first. This is something you’ll see ingrained across our entire organization. We pride ourselves in the fact that customers can always expect to reach a live person and that they will experience our award-winning, best-in-class service. To support the growing number of production business customers, we offer assigned account representatives, a broad suite of supply chain services such as tailored pricing programs, bonded inventory, value-add customization and forecasting services. We also strive to offer an unmatched selection of self-service online tools and resources that streamline high-mix, low volume orders. We know that our customers have mounting pressure to innovate and meet tighter and tighter time to market windows with high demands for accurate forecasting and business continuity. In this challenging environment, immediate availability of product is especially critical and it’s more often than not our breadth of in stock products that allows us to serve customers best by contributing to shorter design cycles, reduced inventory costs and concerns and a competitive edge.

How do you think this distribution business is going to play out 10 years from now? What would Digi-Key’s role be in the future? As the familiar cliché goes, the only constant in our industry will be change. Though we can never precisely predict the future, I’m confident in forecasting that Digi-Key’s growth outside of North America will continue at an accelerated pace. Just as we’ve seen this past year, our business model is being quickly validated by the customers who are choosing us over our competition. Our global sales revenue has increased nearly 10-percent year-over-year which is double the pace of the industry.

I predict we will see high volume requirements driven in the consumer electronics space by mega customers such as Apple and Samsung. However, the innovation, speed, and nimbleness of our unique distribution model will continue to eclipse the completion and allow small and medium size companies to win. Fundamental shifts in component manufacturing, including the increased use of resources such as external foundries, have lowered the barrier to entry for new component manufacturers, and this too will continue to foster innovation. We’ve seen the electronic component distributor market consolidate dramatically over the last 30 years and the larger players like Apple and Samsung clearly illustrate that scale matters. Simultaneously, there is a wide open door for component suppliers and distributors to service the industry’s innovative, engineering customers who identify with the benefits of product availability, knowledgeable resources and high-value supply chain services. Above all else, we seek to maintain an exceptionally high-service attitude that corresponds with our Midwest roots and work ethic. Our goal is to bridge our evergrowing customer base with the latest supplier technology innovations by enabling innovation, design and efficient production. In summary, it is in fact Digi-Key’s hybrid model that enables us to offer unparalleled flexibility and services unique to the industry. ■ Visit:




Copyright 2013, Silicon Frameworks, LLC















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Designing with






By Edward Ayrapetian Senior Design Engineer, Nuvation Engineering

Nuvation has been developing electronic products that use the Global Positioning System (GPS) for many years, but recently there has been an explosion in the GPS design field. Autonomous designs such as vehicles, robotics, consumer electronics, and more all use GPS technology. Weâ&#x20AC;&#x2122;ll be posting a series of articles about how the technology works, and some design considerations for autonomous products. GPS is a constellation of 32 satellites orbiting approximately 12,000 miles above the earth. The satellites make two complete orbits every 24 hours, and are arranged so that about nine satellites are visible from any point on earth at any time. A GPS receiver on earth can determine its precise location if it has an unobstructed view of four of these satellites.




How GPS Works The satellites are placed in highly predictable orbits around earth. Every GPS receiver is programmed with an “Almanac” so that it knows where each satellite is moment by moment. In addition, special ground stations constantly monitor the positions of the satellites and upload any corrections. Satellites transmit this correction data to the receivers on earth. To figure out its location, a GPS receiver establishes the distance to at least four satellites. It then uses trilateration to calculate its location based on the intersection of the four imaginary spheres. The distance to each satellite is determined by measuring the phase shift between a pseudo-random code generated by the receiver and the same code transmitted by each satellite. In order for this to work, the clocks on the satellite and receiver must be precisely synchronized. Satellites use extremely precise atomic clocks, but it would be impractical and cost-prohibitive to have these same clocks on GPS receivers. To get around this limitation, GPS receivers compute the clock error from the distance measurements by essentially solving the reverse problem. Assuming that the clocks are perfectly synchronized, all distance measurements must result in imaginary spheres that intersect at exactly one point. The receiver computes the clock shift that will result in a single point of intersection, thus establishing the offset between its clock and the atomic clock on the satellite. This gives GPS receivers nearatomic clock accuracy for “free” and makes them excellent precision clock references.



“It uses trilateration to calculate its location based on the intersection of the four imaginary spheres.”

Sources of GPS Location Error The accuracy of the GPS is degraded by many factors, most important of which are listed below: The signal path to earth— The signal from the satellite travels at the speed of light while in a vacuum, but is slowed by the earth’s atmosphere. This results in distance measurement errors of around 6 meters in receiver position. Clock errors— Though satellites use highly precise atomic clocks, their accuracy is still a factor due to the high speed of light. Clock errors typically account for around 1.5 meters of positioning error. Orbit errors— The satellites are in highly predictable orbits and are constantly monitored and corrected by ground stations. Still, slight orbital deviations account for around 2.5 meters of positioning error. Multipath— GPS signal reflections from buildings and terrain can result in distance measurements that appear longer. This results in around 0.5 meters in position error. Receiver noise— Noise in the receiver electronics accounts for approximately 0.3 meters of positioning error.




PULSE Over the years, GPS receiver Technology Typical Notes manufacturers have devised Accuracy numerous algorithms and Standard Positioning 10-20 m Also Called â&#x20AC;&#x153;Autonomous techniques resulting in significant Service (SPS) GPSâ&#x20AC;? GPS accuracy improvement using GPS + GLONASS the existing GPS infrastructure. In Standard Positioning < 10 m fact, some of the advanced receive Service (SPS) rs used for land surveying are able GPS + GLONASS to achieve sub-centimeter accuracy. DGPS <5m Accuracy depends on One of the most important proximity to beacon. Rule of techniques is called Differential thumb error increases 1m for every 160km GPS (DGPS). DGPS systems use a stationary GPS receiver placed at WAAS <5m Continental US coverage. Uses a satellite in geostationary a precisely known location as a orbit and therefore works well reference for other stationary or if sky is unobstructed. mobile GPS receivers. The idea Carrier-Phase < 30 cm is that two receivers sufficiently Enhancement (CPGPS) close to each other will receive GPS signals that travel through nearly Relative Kinematic < 20 cm identical slices of the atmosphere. Positioning (RKP) By knowing the precise location of Real-Time Kinematic a receiver, the error introduced by Positioning (RTK) the atmosphere can be computed. Carrier-Phase Tracking < 10 mm High precision, stationary This error is then relayed to other surveying equipment. receivers in the area that can then compensate for the error in their measurements. equipment. In a custom DGPS solution the number This technique works extremely well for of reference stations and their proximity to the receivers within several hundred kilometers mobile receivers can be optimized, which results in of each other. The two largest sources of the highest accuracy but also the greatest expense. error from the atmosphere and satellite Fortunately, governments around the world have orbit can be nearly eliminated. DGPS systems been implementing large-scale DGPS systems that are common in applications requiring high are open to the public. precision, such as automated agricultural



TECH ARTICLE WAAS In the US, the most widely available DGPS system is the Wide Area Augmentation System (WAAS). The WAAS was created by the Federal Aviation Administration and the Department of Transportation for use in precision flight approaches. However, the system is not limited to aviation applications, and many of the commercial GPS receivers intended for maritime and automotive use support WAAS. WAAS provides GPS correction data across North America. Similar systems are available in Europe. GLONASS GLONASS is a space-based satellite navigation system operated by Russia that provides an alternative to GPS. GLONASS and GPS are the only navigation systems with global coverage

and both provide comparable accuracy, with GLONASS being slightly more accurate at higher latitudes (north or south) due to satellite orbital positions. Positioning accuracy can be greatly improved by using both the GPS and GLONASS simultaneously, which would make over 50 satellites available. Many modern satellite receivers support both GPS and GLONASS. Typical GPS Accuracy The table to the left summarizes some of the common GPS technologies and algorithms and the approximate positioning accuracies that can be achieved. Note that accuracy depends on many factors such as the number of visible satellites, receiver surroundings, etc., and are listed for comparison purposes only. Edward Ayrapetian is a member of RF design team at Nuvation Engineering, a firm specializing in electronic development for client products.

RCTM Corrections

Reference Station at a Known Location




Open Source Intel Galileo and Raspberry Pi Boards:




Which One

Should I Use?

The Intel Galileo and the Raspberry Pi (RPi) are both open source, doit-yourself (DIY) electronics hardware development boards featuring embedded processors. Galileo has a new, memory-rich and powerful processor (Quark) and is compatible with existing development accessories from the Arduino suite of open source hardware (OSHW) boards. OSHW has become better known, more widely dispersed, and is rapidly growing since it became more modular (much like chunks of code in Open Source Software) via singular manufacturing entities such as Arduino. Not only are sources openly accessible, but hardware is ready-made and pieces can be simply bolted together. Detailed expertise in technology is not required for implementation. Itâ&#x20AC;&#x2122;s not really fair to compare RPi to Galileo, since the choice should be based upon the goal of the project. Here we detail similarities and differences so that decisions can be made vicariously prior to purchase.




Galileo sports a 400MHz Pentium-class System-on-a-Chip (SoC) called “Quark,” made by Intel, and the board was made cooperatively with Arduino. (Galileo is compatible with existing Arduino shields that fit the Arduino Uno R3.) Raspberry Pi is normally clocked at 700MHz, but can be easily overclocked (with a consequent price of excess heat.) You might think that the comparison ends here, with RPi being faster, but don’t forget to consider details such as the number of instructions accomplished per clock cycle. Both are single core processors. RPi is apparently less efficient in how many instructions it executes per clock cycle. According to the Raspberry Pi Foundation, “The overall real world performance is something like a 300MHz Pentium 2, only with much, much swankier graphics.” Raspberry Pi is best for media such as photos or video, and a Galileo is an excellent choice if you have a project requiring sensors and value utility (requiring memory and processing power) and/or productivity or monitoring (Galileo has a real time clock.) RPi



lends itself to becoming a networked security camera or a media server, but without an analog-to-digital converter, analog sensors would not be easy to connect. Galileo could be used to develop smart everyday “things” with lots of sensors, such as watches, health monitoring or fitness devices, or simply be an inexpensive personal computer running Linux sans all things Arduino. Don’t count on running Windows on Galileo, however, since Windows is a proprietary, closed source operating system (and there is also the problem of faking a ROM BIOS for Windows.) The Galileo datasheet mentions Windows as a compatible operating system. This actually is referring to the host PC that is used to program Galileo. The host can be a Mac, or a PC running Windows or Linux. The Galileo itself comes with an Arduino Linux distribution. Intel has provided development tools for the host PC to run on Windows, Linux, or a MAC. Compilers for each of these host environments (called “cross compilers”) are free.

PRODUCT OVERVIEW The Quark, as an x86 device, has an existing well of software, and historically the vast majority of x86 SoCs are implemented in desktops. (Hint: Set compilers to .586 for Quark x1000.) Intel is eyeing the next wave of technology advances, known as “The Internet of Things” (IoT) or “Industry 4.0”. IoT is a concept in which things (objects, animals, or people) have unique embedded identifiers that automatically communicate with other things (machines, computers, or objects) without direct human intervention, to automatically transfer data for the purpose of self-regulation or for acting in concert on a grand scale. Implementation would result in big data collections and great energy, cost, and time savings with efficiencies gained from every aspect of the interaction of “smart” things. It’s a logical conclusion that Quark demonstrates Intel’s interest in the evolving IoT. Assuming users match to the x86 instruction set, some bleed-over from the desktop domain to the embedded domain (and IoT) is feasible Except that no one really has the Internet of Useful Things worked out yet.

Cost: Galileo vs. Raspberry Pi The Galileo board costs almost twice as much as the Raspberry Pi model B, but there are some hidden costs with RPi, because all that comes in the box is the board. To get RPi running, you need: a USB power supply (at least 700mA at 5V) and an SD card with boot code installed. You may also want a Keyboard, Mouse, HDMI-to-DVI cable (for a monitor), and the informed RPi user will want a powered USB Hub (for parking power-hungry USB devices.) The RPi is not fussy; an old analog TV can be a monitor via the RCA port, but it needs a standard RCA cable. On the other hand, Galileo can be booted and programmed immediately out of the box, since it ships with a USB cable, power supply, and some stand-offs. Galileo boots without the need for external memory like the RPi. Before drawing judgments on the fact that RPi is shipped with no other goodies in the box, it is important to note that Raspberry Pi Foundation is a bonafide, registered nonprofit with a popular product. By 2011, RPi was being mass produced

The Intel Galileo board is certified Arduino and source code is available for download with no software license agreement other than what open source licenses exist on the provided code. Hardware and software source files, including schematics, are provided for download. Intel has good documentation and has seeded the community by giving away several thousand Galileo boards. The Galileo has some differentiating attributes such as PCI Express (PCIe) and a Real Time Clock (RTC), whereas the Raspberry Pi has peripherals well-suited for graphics-intensive applications for HD 1080p streaming video. Galileo is a memory-rich, fairly highperformance 32-bit x86 with traits well-suited to embedded portables or wearable devices: small in size (highly integrated), low power, and fairly low cost with respect to the value that is packed in this SoC. Some major differences: RPi has a GPU. Galileo does not. Galileo has an I2C-controlled I/O expander that runs at 200Hz. I/O that runs through the any of the three “GPIO PWM” blocks on the Galileo schematic is going to be limited to only 200 updates per second. IO13 avoids the limitations of the expander, as well as the UARTs, SPI, I2C, and the ADC. Galileo boots from on-board memory. RPi can only boot from the SD card. Galileo has the first PCIe slot supported by Arduino. Visit:



Both Galileo and RPi are excellent boards, and they both have the most important feature of all: an established open source ecosystem. and sold over one million units within a year. Arduino is not a charity, although it was built with a similar impetus to provide accessibility through affordability, and with a higher goal of educating about embedded hardware development. All other resources are available online.

Booting the Boards Galileo can boot from on-board memory. The RPi boots only from an SD card (4MB or more), which needs an image that can be found on the Foundation website. Thus, RPi requires formatting a card and copying the image before booting for the first time.

Performance Arguably, “performance” is subjective, and depends on what you want to do with the board. Recall that Galileo runs the 400MHz Pentium-class Quark. Raspberry Pi is normally clocked at 700MHz, but since RPi performs fewer calculations per cycle, they are roughly equivalent in this aspect. The big difference is that RPi includes a Graphical Processing unit (GPU) as a co-processor and is well suited to work with high definition graphics. The RPi can provide Blue Ray-quality play back. RPi allows itself to be over-clocked, but heat dissipation increases and it might need a fan to prevent erratic operation when overclocked. Galileo has low power consumption and a lower price point than the MinnowBoard (with



Intel Atom CPU), within reach of the paradigm for open source projects. Galileo sports a 32-bit Pentium ISA-compatible SoC that uses 1/10th the power of the Intel Atom. Galileo could be applied in remote monitoring, but without a CAN bus, Galileo cannot interface easily with some industrial networks. However, WiFi is available with an adapter on the PCIe slot. Over the last decade or so, embedded processors have begun to interact more with the end user over the internet. Embedded devices have begun to look more like desktop in terms of interaction with people and networking, and the demarcation is getting fuzzy. The line gets more fuzzy with the x86based Quark in the OSHW community, since so much software has already been developed to run on x86 from a desktop point of view… and yet Quark is an embedded processor on Galileo. (If you have to program a processor via a host, it’s embedded. Once you install the Linux operating system for use on Galileo, Galileo is a technically a desktop.) Although there is an Open Core movement afoot, OSHW is not always 100% open, because the processor chip is not open source. (Depending on how you look at it: ARM cores are licensed, but not “open” to reuse without cost.) Some manufacturers will make their devices more accessible by allowing users some control over a closedsource chip (e.g., software drivers that allow some manipulation without exposing contents lower in the stack.)

The Major Differences Both Galileo and RPi are excellent boards, and they both have the most important feature of all: an established open source ecosystem. Mouser Electronics (www.mouser. com) offers the Galileo, and many of the products mentioned in this article. With the Galileo, Intel takes the unprecedented step of offering a cheap, easy-touse chip available in an Arduino certified board to deliver the x86 architecture on an embedded platform. Galileo also follows the Arduino paradigm of accessibility through affordable pricing. It’s clear that Intel is taking OSHW seriously, and this can only be a good thing. We will see more open source hardware from Intel. ■


Intel Galileo Board

Raspberry Pi (Model B)

• Board Dimensions: 10cm x 7cm • Operating Voltage: 3.3 V • Processor: Intel® Quark X1000 - SoC • Architecture: Intel® Pentium® Class • Speed: 400MHz • Width, Instruction Set: 32-bit • Real Time Clock: Yes, needs 3.3v coin cell • Cache: 16 KB L1 cache • RAM: 512KB on-chip SRAM 256MB DRAM, dedicated for sketch storage •F  LASH Memory: 8MB NOR Flash (Legacy SPI), for firmware bootloader • EEPROM: 11KB • GPU: No •E  xternal Storage: Micro-SD Card (up to 32GB), and support for an external USB2.0 drive • Video Support: No • Audio Support: No • Status Indication: LED - Board Power • J TAG: 10-pin, Mini-JTAG header, to be used with an in-circuit debugger, OpenOCD**for Quark, and a GUI. The 909-ARM JTAG-2010 converter is useful if you have a 20-pin JTAG device, at •C  ompatibility: Arduino Shields that fit the Arduino Uno R3 (the Arduino 1.0 pinout) 3.3V or 5V shields

• Board Dimensions: 85.60mm x 56mm x 21mm • Operating Voltage: 3.3 V • Processor: Broadcom BCM2835 – SoC • Architecture:  ARM® ARM1176™ (ARM1176JZFS ) • Speed: 700MHz • Width, Instruction Set: 32-bit • Real Time Clock: No •C  ache: 32KB L1 Cache and 128KB L2 Cache shared between the processor and GPU • RAM: 512MB SDRAM (Shared with GPU) •F  LASH Memory: No permanent on-board Flash memory • EEPROM: No •G  PU: Broadcom Dual-core VideoCore IV® Multimedia co-processor •E  xternal Storage: SD-card, and support for an external USB2.0 drive •Video  Support: HDMI – 1080p RCA (analog), without audio DSI* – for touchscreens • Audio Support: HDMI  3.5mm Stereo Audio-out Jack • Status Indication: LED - Board Power LED – SD Card Access LED – LAN Connected LED – LAN Activity • J TAG: Yes, headers P2 and P3. (However, there is no current support to debug the Broadcom and SMSC USB/LAN chip.) •C  ompatibility: Arduino board connectivity through USB. Also, 3rd party board(s) enable support for Arduino shields with Pi. Visit:




A "printf" for FPGAs

by Dave Vandendbout XESS Corp.

::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 50



When I'm developing software, it's nice to be able to run it in a debugger and get detailed traces of what it's doing. But configuring the debugger, setting the breakpoint conditions and then interpreting the trace data is often a daunting task. To avoid that, sometimes (well, a lot of the time) I'll just put a printf into the code to output some variable's value that will help me locate the source of a problem. When I design FPGA systems, the hardware equivalent of the debugger is the logic analyzer module that can be embedded into the FPGA to sample, trigger and store logic signals. Like the debugger, the logic analyzer suffers from the same need to configure it, set triggers and then interpret the output. I'd like to avoid that, but there's no real equivalent of the printf for hardware. (Some might argue that a blinking LED serves that function, but, in my opinion, that's not even good enough to be putc.) So I decided to create my own printf for FPGAs consisting of: • a small HostIoToDut hardware module that can be inserted into a VHDL design to drive test vectors into a DUT (device-under-test) and monitor its response via the JTAG port of an FPGA,

Figure 1: FPGA printf Architecture

• some microcontroller firmware that drives the FPGA JTAG port with the contents of packets received over the USB bus, • a Python library with an API that lets you specify test vectors to send to the DUT and then receive the response over the USB link between the FPGA and the host PC.



PULSE 2. Upon reset, the Opcode register bits were cleared except for the MSB, which was set. With the input selector in position (2), the Opcode register gets loaded with a two-bit opcode which shifts the initially-set MSB into the O flag. This advances the input selector to position (3). 3. Depending upon the value in the Opcode register, the Test Vector/Response shift register exhibits one of these behaviors: NOP: The HostIoToDut module just sits there and does nothing until a reset occurs.

Figure 2: HostIoToDut Module Circuitry

The HostIoToDut Module On the surface, the HostIoToDut module looks very similar to the JTAG circuitry that is already embedded into most FPGAs: it has a shift register that accepts a test vector serially from the TDI pin of the JTAG port, applies it to the DUT in parallel (along with a strobe pulse, if desired), and then grabs the response of the DUT and shifts it out of the TDO pin of the JTAG port. In actuality, however, the HostIoToDut module doesn't use any of the embedded JTAG circuitry (other than accessing the JTAG port I/O signals via the BSCAN primitive of the Xilinx FPGA) because there can be multiple modules that act independently to stimulate and observe the DUT. The circuitry that allows this is shown in Figure 2 and operates like this: 1. Upon reset, the input selector is set to position (1) so that the bits entering through the TDI pin go into the CNTR-ID-I shift register. All the shift register bits are cleared upon reset except the most-significant bit (MSB) of CNTR, which is set. This bit enters and sets the I flag once the ID and CNTR registers have been filled. If the value shifted into the ID register matches the eight-bit ID assigned to this particular instance of the HostIoToDut module (a constant stored in the # register), then the input selector is advanced to position (2).



SIZE: The shift register is loaded with the widths of the test vector expected by the DUT and the response it generates. This information is returned to the Python API so it knows how many bits to send or receive. WRITE: The shift register receives a test vector through the TDI pin and then applies it in parallel to the DUT. A pulse is generated on the Strobe output which can be used to clock the test vector into the DUT. It is possible to repeatedly download and apply new test vectors without leaving this state. READ: The response of the DUT is loaded into the shift register and shifted out through the TDO pin. (Note that the TDO output from the shift register is forced to logic-0 if the values in the ID and # registers for this particular HostIoToDut instance don't match.) 4. A reset is generated when the BSCAN primitive leaves the Shift-DR state. This forces the input selector back to the (1) position from which the entire process can be repeated. You can instantiate several HostIoToDut modules into a design to control and monitor one or more DUTs. All you have to do is assign a different constant to each # register using a generic parameter in the VHDL instantiation and logically-OR all the TDO outputs together. (This works because only one module is active at a given time so all the other modules will output logic-0 on their TDO outputs.) At this point it's natural to ask: "Why use all this complicated ID and Opcode logic? Why not concatenate the shift registers and drive them all at once just like standard JTAG does across multiple chips?" The answer is that it's faster to shift bits in and out of a single HostIoToDut

TECH ARTICLE module rather than having to shift bits through every module just to read or write the bits you want. It also simplifies the API software because it doesn't have to remember and restore the state of all the unaffected modules while changing the state of just one.

The Microcontroller Firmware The microcontroller software performs a couple of relatively straight-forward functions: * It accepts USB packets from the PC containing the values for the TCK, TMS and TDI pins and applies them to the JTAG port. â&#x20AC;˘ It packages the bits output on the TDO pin into USB packets and sends them back to the PC.

The Python API An example of using the Python API to interact with an eight-bit adder is shown in Listing 1. Before executing this script, the FPGA has to be loaded with a bitstream containing the adder circuit and an attached HostIoToDut module with its ID # register set to 4.

Figure 3: Using Multiple HostIoToDut Modules

Listing 1: from xstools.xsdutio import * # Import funcs/classes for PC <=> FPGA link. from random import * # Import some random number generator routines. USB_ID = 0 # USB port index for the XuLA board connected to the host PC. ADDER_ID = 4 # This is the identifier for the adder in the FPGA. # Create an adder intfc obj with two 8-bit inputs, and 8-bit, 1-bit sum, carry outputs. adder = XsDutIo(xsusb_id=USB_ID, module_id=ADDER_ID, dut_input_widths=[8, 8],dut_output_widths=[8, 1]) # Test the adder by iterating through some random inputs. for i in range(0, 100): num1 = randint(0, 255) # Get a random,positive byte in the range [0, 255]. num2 = randint(0, 255) # Get another random, positive byte. (sum, carry) = adder.exec(num1, num2) # # Use the adder in the FPGA. final_sum = sum.unsigned + 256 * carry unsigned # Combine the sum and carry bit. print '%3d + %3d = %4d' % (num1, num2, final_sum), if final_sum == num1 + num2: # Compare Python result to FPGA's. print '==> CORRECT!' # Print this if the sums match. else: print '==> ERROR!!!' # Oops! Something's wrong with the adder.



PULSE The example starts by importing the xsdutio class from the xstools package. Then it creates a USB-to-DUT (XsDutIo) object to communicate to the HostIoToDut module in the FPGA. During creation, the object is told that the adder has two, eight-bit inputs, an eight-bit sum output, and a onebit carry output.

to the address, control and data inputs of a RAM while connecting the RAM data outputs to the module's response input ports. But then you would have to issue multiple commands to write the address and data, strobe the read/write controls, and read back the data from the RAM. That would be slow and error-prone.

The adder is iteratively given 100 test cases where random bytes are assigned to the two inputs. The exec function of the adder object performs the following operations:

For that reason, the HostIoToRam module was built for interfacing to RAMs and other components with a register type of interface (like a UART).

1. It takes the two bytes for the adder inputs and converts them to bit strings.

The I/O interface between the module and a RAM consists of the following signals:

2. It concatenates the two, eight-bit strings and sends them to the HostIoToDut module in the FPGA along with a WRITE opcode. This causes the module to apply the two bit strings to the inputs of the adder.

Clk: A clock input so the HostIoToRam module can synchronize its operations to the RAM clock (if it's a synchronous type).

3. It then sends a READ opcode to the HostIoToDut module and reads back nine bits from the adder.

Data: The bidirectional RAM data bus.

4. It splits the nine bits into an eight-bit sum and a one-bit carry and returns these as two, individual bit strings.

Write: The RAM write control line.

The sum and carry bitstrings are converted to unsigned integers and combined to get the final sum from the adder. Then this is compared to the sum calculated within the Python script to detect whether any errors occurred.

Address: The RAM address bus.

Read: The RAM read control line.

Done: An input for the acknowledgement signal from the RAM when the memory operation has completed.

It's easy to extend this example to test multiple DUTs in an FPGA by just creating additional XsDutIo class objects with distinct IDs (and instantiating more HostIoToDut modules in the FPGA, of course). Since this is done with Python, you have access to all the other Python libraries for writing your testing scripts. You can even put GUI front-ends on them if that's your thing.

Extending the Concept to RAMs While it's nice to have the HostIoToDut module to observe and control the digital circuitry inside an FPGA, there's one common type of design entity that it doesn't really support: RAM-like components. Of course, you could instantiate a HostIoToDut module and connect the test vector output ports



Figure 4: HostIoToRam Interface

TECH ARTICLE The internal circuitry is very similar to the HostIoToDut module except the HostIoToRam module has a more complicated state machine to manage the read/write operations. Viewed externally, both types of modules operate similarly and can be combined together to control and monitor any FPGA design. The opcodes supported by the HostIoToRam module are: NOP: The HostIoToRam module just sits there and does nothing until a reset occurs. SIZE: The shift register is loaded with the widths of the RAM address and data buses. This information is returned to the Python API so it knows how many bits to send or receive for memory operations. WRITE: The shift register receives an address and data word through the TDI pin and then applies it to the RAM. A pulse is generated on the write control line which loads the data into the RAM. Any subsequent bits which enter through TDI are written to the next RAM address (the address can be either incremented or decremented). This makes it easy and fast to write data to a range of sequential RAM addresses without having to issue individual WRITE commands.

READ: The shift register receives an address through the TDI pin and then applies it to the RAM. A pulse is generated on the read control line which gets the data from the RAM address and loads it into the shift register. The data bits in the register are shifted out through the TDO pin. Any subsequent bit shifts trigger a read of the next RAM address (the address can be either incremented or decremented). This makes it easy and fast to read data from a range of sequential RAM addresses without having to issue individual READ commands. Listing 2 shows a simple example of using the Python API to write and read a RAM in the FPGA. Before executing this script, the FPGA has to be loaded with a bitstream containing a RAM attached to a HostIoToRam module with its ID # register set to 10. The example starts by importing the xsmemio class and creating a USB-to-RAM (XsMemIo) object to communicate with the HostIoToRam module in the FPGA. (There's no need to tell the object the address and data widths of the RAM since it can use the SIZE opcode to find these directly.) Then an array of 100 random numbers is created and written to the RAM using the write method of the ram object. The 100 values are read back (as bit strings) into

Listing 2: from xstools.xsmemio import * # Import funcs/classes for PC <=> FPGA link. from random import * # Import some random number generator routines. USB_ID = 0 # USB port index for the XuLA board connected to the host PC. RAM_ID = 10 # This is the identifier for the RAM in the FPGA. ram = XsMemIo(xsusb_id=USB_ID, module_id=RAM_ID) # Create a RAM interface object. test_data = [randint(0,255) for d in range(100)] # Create array of 100 random unsigned integers. ram.write(0, test_data) # Write test data to RAM, starting at address 0. ram_data =, 100) # Read back 100 words of data from the RAM, starting at address 0. # Compare data from the RAM to the test data to see if there are any mismatches. for addr in range(0, 100): if test_data[addr] != ram data[addr].unsigned: print 'ERROR at address %d: %d != %d', addr, test_data[addr], ram_data[addr].unsigned



PULSE Getting All This Stuff The VHDL for the various HostIoTo* modules is open-source and stored on GitHub, as is the microcontroller firmware. These are parts of the open hardware XuLA2 FPGA board. You can view the open source code for the Python API on GitHub, but you may just want to install the latest executable package using the command pip install xstools. (You'll need Python to be installed, first.)

About the Author

Figure 5: HostIo Interface to an External DAC

another array with the read method. Then the two arrays are compared to see if they match (which they should).

Extending the Concept to External Chips Combining the HostIoToRam module with other types of interface modules extends the control and monitoring capabilities to chips outside the FPGA. For example, Figure 5 depicts how you can control and monitor a digital-to-analog (DAC) chip with an SPI slave interface by using the HostIoToRam module to read/write the control/data registers of an SPI master component instantiated in the FPGA. The HostIoToRam and SPI master modules can be rolled into a HostIoToSpi module to make it easier to instantiate in an FPGA design. Then a new class can be added to the Python API that lets you perform reads and writes to registers in the SPI device.



David E. Vandenbout earned a B.S.E.E. degree from North Carolina State University (NCSU) in 1978 and an M.S.E.E. from M.I.T. in 1979. He worked as a Member of Technical Staff at Bell Telephone Laboratories from 19781983 until they suggested he explore other career opportunities. He completed his Ph.D. at NCSU in 1987 and worked there as an Assistant Professor doing research in the areas of neural networks, statistical physics, computer tomography, and FPGA-based rapid-prototyping. After publishing over 45 journal articles, conference papers and book chapters, he left in 1993 due to an allergic reaction to the passive voice. In 1990, he was one of the founders of X Engineering Software Systems Corp. (XESS), a company that originally developed software for X11based scientific workstations until they found out nobody actually wanted to pay any money for that. He re-directed XESS so that it now develops and sells low-cost, opensource, FPGA-based hardware. XESS has developed and delivered boards to thousands of individuals and hundreds of corporations and universities in almost every country in the world (still waiting on Antarctica). XESS FPGA boards have been used in everything from classroom instruction to digital video processing to cracking the cryptographic codes of the SpeedPass system. â&#x2013;

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