Matt LeeFounder & Technical

Team Lead at Oscium

Electrical Engineering Community

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CONTENTSPULSE

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4Matt LeeOSCIUM

A conversation with Oscium’s Technical Team Lead on how they are paving the way for the

future of test equipment.

10Featured ProductsThis week’s latest products from EEWeb.

14Flexible PCB TechnologyWith the demand for portable electronics ever increasing, there comes the need for solutions

that combine functionality with flexbility.

18Impact of Easy-to-Use

Microcontrollersby Alex Toombs

How simple microcontrollers like Raspberry Pi and Arduino are altering the way some high

schools and universities educate.

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Oscium creates test equipment that utilizes the intuitive features and touchscreen technology of mobile devices

like the iPad and iPhone. Founded by brothers Matt and Bryan Lee in January of 2010, Oscium existed for an entire

year before releasing its first product. During that year, the Oscium engineering team was developing and fine-tuning its first product--the iMSO scope--in its Oklahoma City offices. The company has since expanded and has recently won multiple design and engineering awards for their WiPry

family of products.

We spoke with Matt Lee, the Co-founder and Technical Team Lead at Oscium, about the company’s growth, why they targeted mobile devices for

their test equipment products, and why he believes that Oscium is paving the way for the future of test equipment.

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INTERVIEW

Oscium creates test equipment that utilizes the intuitive features and touchscreen technology of mobile devices

like the iPad and iPhone. Founded by brothers Matt and Bryan Lee in January of 2010, Oscium existed for an entire

year before releasing its first product. During that year, the Oscium engineering team was developing and fine-tuning its first product--the iMSO scope--in its Oklahoma City offices. The company has since expanded and has recently won multiple design and engineering awards for their WiPry

family of products.

We spoke with Matt Lee, the Co-founder and Technical Team Lead at Oscium, about the company’s growth, why they targeted mobile devices for

their test equipment products, and why he believes that Oscium is paving the way for the future of test equipment.

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Could you give us an overview of Oscium’s current products?

In 2011, we released iMSO-104, our mixed signal oscilloscope for iOS. The app is downloaded through the Apple App Store. You can then plug our hardware into your iPad, iPhone, iPod and you have an oscilloscope with one channel of analog and four digital channels. This product required us to rethink how test equipment works so it could function on our platform. We’ve gone through several iterations of our software to make it more intuitive. We want it to be so simple that anyone can pick it up and understand how it works.

Our other product is a spectrum analyzer and dynamic power meter, which we call WiPry-Combo. There are two modes of operation. One is a spectrum analyzer which gives you a view of the 2.4-2.5 GHz ISM band. The other is a dynamic power meter. Our power meter is very different from the typical power meters you see in the marketplace. It allows you to look at the time usage, duty cycle and on/off times from 100 MHz all the way to 2.7 GHz. The WiPry family is divided into two products. We have a spectrum analyzer for the IT professional called WiPry-Spectrum.

With LogiScope, another product, we made a really big advancement. It contains a CPLD that does the data capture and also includes sophisticated triggering options. What we are ultimately trying to do with our products is push the limits of low-power solutions. One of the things we like about our current platform is portability. You can pull out your oscilloscope or your logic analyzer

iMSO-104 Mixed Signal Oscilloscope for the iPad

LogiScope Logic Analyzer or the iPad

WiPry-Combo Peak Power Meter & Spectrum Analyzerfor the iPhone

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INTERVIEWanywhere. It’s small enough to fit in your pocket making it easy to use in the field. The scope uses the battery on the iPad so no additional charge is needed. We are always trying to bring our products to the next level to give our customers exactly what they need.

How do you go about making software improvements?

The platform we have allows us to push software updates quickly. If you look at the product, we’ve made three significant UI changes, almost entire rewrites. I think we’ve honed in on a platform that is user friendly. It is easy to navigate and allows easy access to items you want. We’re always looking to improve our products.

How has the shift to the lightning connector affected your business?

Initially, it was significant because there was no clarity around whether 30-pin accessories would work with the new connector. But now we’ve been able to test and verify that all of our products work with the lightning adapter. We are fully compatible with all of the newer iOS products.

What is your management style?

Originally, I preferred to be a heads-down engineer, but now my role is to guide the direction of our team. I’ve learned that it is important to be able to do both. If you are only a manager, you can’t really communicate well with your engineers. And if you’re only an engineer, you risk missing the big picture. You need to be a little bit of both; you need to be well-rounded.

As we started producing more products, my bandwidth was being decreased so it made sense for us to hire more people and to let them run with certain parts of projects. This shift in thinking has added tremendous value. We are a highly functioning team.

My management style is to give our engineers and the people I work with the ability to take the initiative while working toward a clearly defined goal. Trying to micromanage stifles creativity and innovation. It puts a damper

on the whole process. I would rather be hands-off and let creativity flower instead of trying to drive creativity by minutes and increments. At the same time it is important to have weekly meetings and updates on progress to make sure we are goal oriented. Finding the right balance can be somewhat challenging.

What’s the secret to having an innovative DNA?

I try to look at products differently than everyone else. I try to ask myself not just how can it be changed, but how can it be improved. Sometimes the change is small. Sometimes it is big. It just needs to be approached from a different perspective. Our team tries to keep the needs of the customer paramount. This approach is really important when you are doing product development, and it’s harder than it looks. There are plenty of people that think they can make a product but there are many failures out there. Businesses fail all the time. It’s very important that you have a good understanding of your customer and what they actually need.

“What we are ultimately trying to do with our products is push the limits of

low-power solutions. One of the things we like about our current platform is portability. You can pull out your oscilloscope or your logic analyzer anywhere. It’s small enough to fit in

your pocket making it easy to use in the field.”

Oscium’s iMSO-104 was recognized as one of the 100 most technologically significant products of 2012 by the editors of R&D Magazine. Oscium’s mobile-friendly oscilloscope was awarded for

merging the test equipment industry with the smartphone and tablet industries.

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What is your target market for your products?

Our customer is the next generation of inventors. This includes educators, on-the-go technicians, and hobbyists. For us, education is the key. As the younger generation comes up, touch is what they know. A child can learn to use a tablet and smartphone before they can learn to talk. We try to design products which fit this simple and intuitive model.

Have you had any upside surprises with Oscium?

Even though I thought our mixed signal oscilloscope was a cool product, I was surprised at how well it was received. The Apple hardware gave us the ability to do things no one else in the industry was doing. Multi-touch and pinch-to-zoom make setting up and capturing the event easy because you are actually looking at the event.

We did a video with the punch line ‘count the hairs on your bug.’ This example drives home my own surprise at how these capabilities came together. Marrying the intuitiveness of the platform transformed the experience. Once someone has picked up our tool and used it, they love it. I still have a benchtop scope on my desk, and it’s great when I need to look at faster signals. But when I want to look at something quick to verify the signal, our scope works perfectly, and my tablet is always out for email and messaging. I can just plug it in and go. It makes the tablet interface universal. We’re adding test equipment abilities to an already ubiquitous interface. ■

Bryan Lee, President & Matt Lee

“ Our customer is the next generation of inventors. This includes educators, on-the-go technicians, and hobbyists. For us, education is the key.”

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World’s Smallest I/O InterconnectThe Molex HDMI™ Type-D Micro Connectors are the world’s smallest standard I/O interconnect for hand-held consumer electronics. The HDMI Type-D Micro Connec-tors are half the size of the current Type-C (Mini) connectors, but deliver equivalent mechanical strength and electrical characteristics, as well as meet HDMI 1.4 specifi-cations. The Molex HDMI Cable Assembly is Type-D to Type-A. The Molex HDMI Type-D Micro Connectors deliver high-definition video and images from digital cameras and mobile devices to flat-panel screens...Read More

Zero No-Load Off-Line SwitcherLinkZero-LP, an upgrade to PI’s popular LinkSwitch-LP, incorporates new technology which enables the device to automatically enter into and wake up from no-load mode while disipating less than 5 mW – substantially less than the IEC definition of zero no-load power consumption. The tightly specified FEEDBACK pin voltage reference enables universal input primary side regulated power supplies with accurate constant voltage from 5% to full load. Start-up and operating power are derived directly from the DRAIN pin which eliminates start-up circuitry...Read More

9A Three-Phase Switching RegulatorThe MAX8973A high-efficiency, three-phase, DC-DC step-down switching regulator delivers up to 9A of output current in a compact footprint with excellent transient response. Each phase operates at a 2MHz fixed frequency, allowing the use of small magnetic components. Maxim Integrated’s proprietary Rotational Phase Spreading algorithm optimizes efficiency at low output currents. Software-selectable forced-PWM mode allows either fixed-frequency operation, or improved efficiency at light load with a variable frequency in skip mode...Read More

Arduino Compatible chipKIT BoardsMicrochip Technology Inc. announced the expansion of its Arduino™ compatible chipKIT™ platform ecosystem, with new tools from partners Digilent, Inc., the Fair Use Building and Research (FUBAR) Labs, and Schmalz Haus LLC. These new tools are based on Microchip’s 32-bit PIC32 microcontrollers (MCUs) in prototyping-friendly, low pin count SOIC or SPDIP packages, which were previously more common in 8-bit MCUs, for the Arduino community...Read More

Low Noise 1.8V CMOS Op-AmpThe OPA2314 is a dual channel operational amplifier and represents a new genera-tion of low-power, generalpurpose CMOS amplifiers. Rail-to-rail input and output swings, low quiescent current (150 μA typ at 5.0 VS) combined with a wide band-width of 3 MHz, and very low noise (14 nV/√Hz at 1 kHz) make this family very at-tractive for a variety of battery-powered applications that require a good balance between cost and performance. The low input bias current supports applications with mega-ohm source impedances...Read More

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FEATURED PRODUCTS

Automotive NFC / RFID TransceiverThe MLX90132 is a 13.56MHz RFID/NFC reader IC. It has been de-signed to handle sub-carrier frequencies from 106 to 848 kHz and baud rates up to 848kbit/s. The robust and flexible receiver part of the MLX90132 enables designers of NFC/RFID reader devices to fit their system requirements and to address the main communication standards with the same device.

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Three-Phase MOSFET Controller ICAllegro MicroSystems, LLC introduces a new three-phase MOSFET controller IC that is designed for pulse width modulated (PWM) current control of three-phase brushless DC motors. The A4915 is capable of high current gate drive for 6 all N-channel power MOSFETs. An internal charge pump ensures gate drive down to 7 V supply and pro-vides limited gate drive down to 5 V. A bootstrap capacitor is used to generate a sup-ply voltage greater than the source voltage of the high side MOSFET, a requirement for N-channel MOSFETs...Read More

Small Cell RF Front-End SolutionsAvago Technologies announced two new RF power amplifiers (PAs), the MGA-43728 and MGA-43828, and a new WiFi FBAR filter, the ACFF-1024, designed specifically for small cell base transceiver station (BTS) applications. Expanding upon Avago’s proven MGA-43×28 PA family, the MGA-43728 and MGA-43828 are respectively new UMTS/LTE Band 7 and Band 8 PAs featuring high linearity, gain and power-added efficiency (PAE) with integrated power detector and shutdown function. The ACFF-1024 is a new miniature band-pass filter optimized for use in the 2.4GHz ISM band....Read More

High Performance 32-Bit DACAK4414 is a 32-bit DAC, which corresponds to BD systems. An internal circuit in-cludes newly developed 32bit Digital Filter for better sound quality achieving low distortion characteristics and wide dynamic range. The AK4414 has full differential SCF outputs, removing the need for AC coupling capacitors and increasing per-formance for systems with excessive clock jitter. The AK4414 accepts 216kHz PCM data and 1-bit DSD data, ideal for a wide range of applications including DVD-Audio and SACD...Read More

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6-Channel 45V Capable LED DriverThe ISL97671 is a 6-Channel 45V dual dimming capable LED driver that can be used with either SMBus/I2C or PWM signal for dimming control. The ISL97671 drives 6 channels of LED to support 78 LEDs from 4.5V to 26V or 48 LEDs from a boost supply of 2.7V to 26V and a separate 5V bias on the ISL97671 VIN pin. The ISL97671 compensates for non-uniformity of the forward voltage drops in the LED strings with its 6 voltage controlled-current source channels. Its headroom control monitors the highest LED forward voltage string for output regulation, to minimize the voltage headroom and power loss in a typical multi-string operation...Read More

MCUs with Low Power & USB CapabilityRenesas Electronics Corporation has introduced the first in its RX100 Series of powerful 32-bit microcontrollers (MCUs)—the new RX111 Group. The RX111 is produced on an ultra low power zero wait state flash process sup-porting market leading 32-bit power consumption / performance levels as well as supporting fast wake-up, with a wide range of standard peripherals and multiple safety functions as well as an integrated USB 2.0 peripheral supporting host, device and on-the-go functionality. The RX111 devices are supported by IAR Systems’ EWRX tool chain compiler and IDE...Read More

Low Capacitance TVS Diode ArrayLittelfuse, Inc. announced it has developed a new SP3012-06UTG Low Ca-pacitance ESD Protection TVS Diode Array (SPA® Devices). The new prod-uct is optimized for protecting sensitive chipsets on high-speed data lines from any external ESD (electrostatic discharge) event. Typical applications include USB 3.0 and HDMI port protection on LCD/PDP TVs, DVD/Blu-ray players, desktop PCs, MP3/PMPs, set top boxes, smartphones, ultrabooks/notebooks and digital cameras. Samples are available now for bulk orders; sample requests can be placed through authorized Littelfuse distributors worldwide...Read More

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FEATURED PRODUCTS

2-Channel Stereo Audio CODECIDT’s STAC9750/9751 are general purpose, full duplex, audio CODECs con-forming to the analog component specification of AC’97 (Audio CODEC 97 Component Specification Rev. 2.2). They have 18-bit ADCs and 20-bit DACs. The STAC9750/9751 incorporate IDT’s proprietary ΣΔ technology to achieve a DAC SNR in excess of 89dB. The DACs, ADCs and mixer are inte-grated with analog I/ Os, which include four analog line-level stereo inputs, two analog line-level mono inputs, two stereo outputs, and one mono out-put channel. The STAC9750/9751 include digital input/output capability for support of modern PC systems and also an output that supports the SPDIF format...Read More

200A Pulsed Current SourceThe PCX-9200I is a 200A pulsed current source and is capable of supplying a bias current of up to 60 Amps. The PCX-9200I is available with an inter-nal power supply for stand-alone operation. The Graphical User Interface provides intuitive control of the PCX-9000. It is a microprocessor controlled touch screen that communicates to all modules through a simple com-bination of front panel controls and touch screen technology within the system. The Communications Module allows the user to use a computer to communicate to the instrument via RS232, GPIB or Ethernet. Communi-cation settings are accessed easily through the touch screen menu and stored in non volatile memory so they are ready to be used upon instru-ment start up...Read More

1 Mbit & 2 Mbit FRAM ProductsFujitsu Semiconductor America announced two new FRAM products featuring 1 Mbit and 2 Mbits of memory. The MB85RS1MT and MB85RS2MT, the largest-capacity, serial-interface FRAM products offered by Fujitsu, will be available in sample quantities at the end of March. The MB85RS1MT and MB85RS2MT FRAMs offer features that are ideal for smart me-ters, industrial machinery and medical devices, including high endurance, higher writing speed, larger density and low power consumption. The new FRAMs can support 10 trillion writing cycles, an endurance roughly 10 times greater than previous ferroelectric memories from Fujitsu and superior to other nonvol-atile memories by at least a million times. Memory devices using FRAM consume 92 percent less power during writing compared to identical-capacity EEPROMs, and feature a writing speed 920 times faster...Read More

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Latest Material and Construction Methods Provide the Highest

Quality Rigid-Flex PCB’s

Latest Material and Construction Methods Provide the Highest

Quality Rigid-Flex PCB’s

Latest Material and Construction Methods Provide the Highest

Quality Rigid-Flex PCB’s ith the demand for portable electronics ever increasing,

the need to produce more compact devices with complex capabilities calls for engineering solutions that combine

functionality with flexibility.

W

By Paul Tome, Flex Circuit Product Manager

Epec Engineered Technologies

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TECH ARTICLE

Latest Material and Construction Methods Provide the Highest

Quality Rigid-Flex PCB’s

Latest Material and Construction Methods Provide the Highest

Quality Rigid-Flex PCB’s

Latest Material and Construction Methods Provide the Highest

Quality Rigid-Flex PCB’s ith the demand for portable electronics ever increasing,

the need to produce more compact devices with complex capabilities calls for engineering solutions that combine

functionality with flexibility.

W

By Paul Tome, Flex Circuit Product Manager

Epec Engineered Technologies

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Rigid-Flex circuits can be shaped to fit where no other design solution can. They are an integrated hybrid of printed

circuit board and flex circuit technology and exhibit the benefits of each. They allow substantially greater freedom of packaging geometry and a significant reduction of interconnects while retaining the precision, density and repeatability of printed circuit board technology.

Rigid-Flex circuit design has evolved significantly over the past decade. Modern designs require the rigid areas to be fully capable “rigid” boards. The same limits of complexity and density are pushed as in modern PCB’s, including: fine lines/spacing, high aspect ratio vias, blind and

buried vias, high layer counts (20+), higher operating temperatures, and RoHS assembly compliance.

However, some of these advances created potential via and plated hole reliability issues. Older design methods used materials and constructions containing many layers of “adhesives” within the rigid area constructions. Due to adhesives having a high coefficient of thermal expansion (10 to 20 times that of FR-4), vias are placed under a significant amount of stress during thermal cycles that occur during RoHS assembly, multiple assembly cycles, and higher system & component operating temperatures. The use of adhesives within the rigid areas sometimes caused cracks to form in the copper plating within via holes (Figure 1).

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Figure 1: The use of adhesives within the rigid areas may cause cracks to form in the copper plating within via holes.

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TECH ARTICLEAdhesives, within a rigid-flex design, may come from any of three sources: the copper clad flex laminate itself, the coverlay construction method used and the material used to bond the rigid and flex layers into the final structure. To solve the issue of via reliability, manufacturers, material suppliers and industry standards organizations have worked together to develop solutions and specifications that eliminate or minimize the use of adhesives in these areas.

To address the use of adhesives in copper clad flex laminate, “adhesiveless” constructions were developed. Previously, copper layers were bonded to the polyimide core with either an acrylic or modified epoxy adhesive (Figure 2a). An adhesiveless laminate has the copper directly attached to the polyimide core (Figure 2b). Eliminating the adhesive bond layers allows for thinner constructions and more flexible design with vastly improved reliability. In addition adhesiveless copper clad laminates have higher operating temperature ratings, higher copper peel strengths, and the desired reduced Z-Axis thermal expansion stress on vias.

Coverlay constructions also previously presented a problem in rigid-flex designs. Older methods use full coverage coverlays that extend throughout the entire rigid area(s). Vias and plated though holes would then be exposed to the excessive Z-Axis thermal expansion stress applied by the coverlay adhesive. To solve this issue, selective coverlay constructions were developed so that coverlays are restricted to the exposed flex areas only and have a maximum 0.050” interface within the rigid areas. (Figure 3). PTH and via holes are restricted from this interface area.

Lastly, rigid and flex layers are now laminated into the final structure, using high temp no-flow FR4 prepregs rather than layers of flex adhesives. This provides a structure as dimensionally stable in the Z-Axis as standard rigid PCB designs.

IPC 2223C Sectional Design Standard for Flexible Printed Boards lists all of the above as key elements in the design of a reliable rigid-flex design that meets today’s requirements.

Epec manufactures single, double, and multi-layer flex circuits using modern rigid-flex materials and construction. Designs comply with IPC 2223C standards, which define the elimination/minimization of adhesive use within rigid areas, use of adhesiveless based substrates, and use of selective/partial coverlay construction.

Epec Engineered Technologies designs and manufactures custom, build-to-print products, for all sectors of the electronics industry. Their solutions provide a cost savings, technical resource or delivery advantage for their customers.

With employees worldwide, Epec is dedicated to innovating solutions that deliver the highest quality products to market, faster. ■

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Figure 2a: Copper layers bonded to the polyimide core with either an crylic or modified epoxy adhesive.

Figure 2b: An adhesiveless laminate has the copper directly to the polyimide core.

Figure 3: Coverlays restricted to the exposed flex areas only and have a maximum 0.0050” interface within the rigid areas.

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TECH ARTICLE

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However, it has been up to highly knowledge-able engineers to write and compile code specific to these microcontrollers, meaning that those who have had good ideas but lacked certain skills could not bring their crea-tions to life. Proprietary compilers are often used with separate toolchains for each itera-tion of the device, effectively adding several layers of abstraction before worrying about actually writing the software for the processor to execute. Over the last decade, this confu-sion has given way to several important and impressive products that have changed the scale of the electronics community today, and are challenging traditional notions of engineering education. Platforms like Ardui-no and Raspberry Pi are open source and cheaply available to anyone. These products have not only impacted the electronics and creative communities across the world, but also have altered the way some high schools and universities educate.

History of ArduinoFrustrated by the difficulty inherent to most prototyping solutions at the time, Massimo Banzi and David Cuartielles set out to make something better that students could use to rapidly change designs. They came up with the Arduino, heralded as kicking off the “maker” movement that has spread rapidly today. Arduino is an open source hardware and software platform that provides a board and unified bootloader for a variety of Atmega microprocessors. Instead of requiring years of education, Arduino’s simplified language and programming interface allow nearly anyone to bring their creations into reality.

Additionally, the open source nature of the project means that a wealth of knowledge exists for free on the internet pertaining to thousands of different projects. Today, Arduino is one of the most accessible microcontrollers available to budding engineers and makers looking to extend, automate, or control a project.

Banzi and Cuartielles started Arduino without any idea of what a phenomenon it would become. Dissatisfied with the high cost and limitations of alternatives like the BASIC Stamp, Banzi sought to create a prototyping board that would more easily introduce students to the field of physical computing. Whereas the Stamp was about $100, Banzi wanted to make his vision cost less than a dinner for two— around $30. And as someone passionate about the open source movement, Banzi released all hardware and software for the device under the Creative Commons license, typically used for works of literature or music. After several revisions and collaborations, a design was released that offered a complete solution like what Banzi was looking for. The Arduino itself is little more than a breakout for an Atmega chip with a crystal, voltage regulator, and some capacitors. Later version also included a USB chip and port, making the device much easier to program than it would be with ICSP or FTDI. A picture of a 2005 $30 Arduino board is shown in Figure 1.

Applications of ArduinoThe goal for Arduino was to allow anyone to use it, replicate it, or alter it on their own without having to give Banzi and others one cent.

Easy-to-use microcontrollers have not only impacted the electronics and creative communities across the world, but also have altered the way some high schools and universities educate.

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TECH ARTICLEDozens of different Arduino boards from many different manufacturers are now available, all serving largely the same function. Arduino’s software is written in the Programming language. It is compiled by the Arduino IDE, which includes many simple examples and different libraries, and uploaded to the board via the built-in programmer. The IDE, and a snippet of code that causes an LED on port 13 to turn on or off every second, is shown in Figure 2.

The simplicity of the Arduino setup has been hailed as a large part of the product’s success. But the biggest thing going for Arduino these days is the community that has grown around it. Developers who wanted to do something originally, like interface with a serial LCD to display a Twitter feed in real-time, had to create libraries to communicate with and control the peripheral they wanted to utilize. These developers have often open sourced these libraries, many of which are kept on the Arduino website and are easily accessible. For instance, in the ND PCR project I wrote about earlier and contribute to, we were able to use a library to control the serial LCD for outputting pertinent data, a library to map a 12-digit keypad for inputs, a PID controller library to control the amount of current flowing through the heating elements, and a serial library to easily control communication back over the serial port. Arduino has been used for Twitter displays and as the centerpiece for a smart RFID-controlled kegerator, as in the Kegbot project. Hackers have used Arduinos to break into hotel rooms secured by Onity programmable locks, as well. Robotics enthusiasts continue to improve upon their machines, many of which are based upon the platform as well. With satellites now being powered by several year-old Android phones, Arduino seems to have no limit to its potential.

The Raspberry PiRaspberry Pi is a slightly different device with a similar goal. Launched in February 2012, the designers of the Raspberry Pi sought to bring a cheap, Linux-based computer with a number of hardware interfaces in order to get students interested in learning about computer science from a young age. They have proven popular since, selling out at both the $25 and $35 price points many times over the last year. The game Minecraft has been compiled for the device, as has popular media center application XBMC, along

Figure 1: Arduino board (courtesy of Arduino and protected by the Creative Commons License)

Figure 2: Arduino IDE with Blink Example (courtesy of Wikimedia user Lemio)

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with many distributions of Linux. Each board contains an ARM processor, 256 MB to 512 MB of RAM, an SD card slot, USB ports, HDMI, 3.5 mm audio, and in the case of the model B, an ethernet port for internet connectivity. The model A Raspberry Pi is shown above as Figure 3.

These cheap card-sized devices have been similarly revolutionary. Raspberry Pi has served as a base for a media center for many, but has been used as an educational tool in other instances. The University of Cambridge bases their operating systems course on the Raspberry Pi as a universal platform that is easier to understand than many modern computers. Schools and other organizations have seen the potential of these cheap computers as workstations as well.

Shaping Future EducationMany engineers have complained about the simplicity that Arduino offers to programmers. Compared to other microcontrollers programmed with C or Assembly, Arduino obscures much more of the technical details in favor of a streamlined process that favors rapid prototyping over complete

understanding. The problem with that argument is that the complexity of older microcontrollers is enough to turn most people off from learning more about the many possibilities that microprocessors offer. People can be pulled in by Arduino and learn more details later as they seek a more powerful chip, or simply as they want to learn more about how it all works. Without Arduino, those with desire to create that lack technical knowledge may never get to experiment and prototype. Personally, I hope that these low-cost microcontrollers can revolutionize the education for electrical engineers and computer scientists. Having low-cost devices available to schools worldwide means that people everywhere can get access to technology at an early age. Teaching people about operating systems with Raspberry Pi will enable the next generation of developers to improve upon the Linux kernel and OS, while giving younger kids access to Arduino will allow them to see that programming is not nearly as hard as people make it out to be. With how important computers are to everyday life, it is surprising that these innovations haven’t spread further than they have. ■

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Figure 3: Raspberry Pi Board (courtesy of eLinux.org user Jamodio)

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Power Factor Correction ControllersISL6730A, ISL6730B, ISL6730C, ISL6730DThe ISL6730A, ISL6730B, ISL6730C, ISL6730D are active power factor correction (PFC) controller ICs that use a boost topology. (ISL6730B, ISL6730C, ISL6730D are Coming Soon.) The controllers are suitable for AC/DC power systems, up to 2kW and over the universal line input.

The ISL6730A, ISL6730B, ISL6730C, ISL6730D are operated in continuous current mode. Accurate input current shaping is achieved with a current error amplifier. A patent pending breakthrough negative capacitance technology minimizes zero crossing distortion and reduces the magnetic components size. The small external components result in a low cost design without sacrificing performance.

The internally clamped 12.5V gate driver delivers 1.5A peak current to the external power MOSFET. The ISL6730A, ISL6730B, ISL6730C, ISL6730D provide a highly reliable system that is fully protected. Protection features include cycle-by-cycle overcurrent, over power limit, over-temperature, input brownout, output overvoltage and undervoltage protection.

The ISL6730A, ISL6730B provide excellent power efficiency and transitions into a power saving skip mode during light load conditions, thus improving efficiency automatically. The ISL6730A, ISL6730B, ISL6730C, ISL6730D can be shut down by pulling the FB pin below 0.5V or grounding the BO pin. The ISL6730C, ISL6730D have no skip mode.

Two switching frequency options are provided. The ISL6730B, ISL6730D switch at 62kHz, and the ISL6730A, ISL6730C switch at 124kHz.

Features• Reduce component size requirements

- Enables smaller, thinner AC/DC adapters- Choke and cap size can be reduced by 66%- Lower cost of materials

• Excellent power factor over line and load regulation- Internal current compensation- CCM Mode with Patent pending IP for smaller EMI filter

• Better light load efficiency- Automatic pulse skipping- Programmable or automatic shutdown

• High reliable design- Cycle-by-cycle current limit- Input average power limit- OVP and OTP protection- Input brownout protection

• Small 10 Ld MSOP package

Applications• Desktop computer AC/DC adaptor

• Laptop computer AC/DC adaptor

• TV AC/DC power supply

• AC/DC brick converters

FIGURE 1. TYPICAL APPLICATION FIGURE 2. PFC EFFICIENCY

+

ISL6730

VCCISEN

ICOMP

VIN

GATEGND

FB

BO VREG

COMP

VLINE VOUT

VI

OUTPUT POWER (W)

EFFI

CIE

NC

Y (%

)

ISL6730C

ISL6730A, SKIP

100

95

60

65

70

90

85

80

75

0 20 40 60 80 100

TABLE 1. KEY DIFFERENCES IN FAMILY OF ISL6730

VERSION ISL6730A ISL6730B ISL6730C ISL6730D

Switching Frequency 124kHz 62kHz 124kHz 62kHz

Skip Mode Yes-Fixed Yes-Fixed No No

February 26, 2013FN8258.0

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2013All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

Get the Datasheet and Order Samples

http://www.intersil.com

http://bit.ly/SJ9ugm

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101IF, CASE, and WHEN in a Process

Paul ClarkeElectronics Design

Engineer

VHDLPart 4

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FEATURED ARTICLE

101IF, CASE, and WHEN in a Process

Paul ClarkeElectronics Design

Engineer

VHDLPart 4

In the third installment of this VHDL series, we discussed logic gates and adders. Now let’s move on to some basic VHDL structure. All HDL languages bridge what many think is a strange brew of hard-ware and software. In this article, we’ll look at the ‘IF’ and ‘CASE’ statements. These are most often found in writing software for lan-guages like C or Java. In VHDL they work just the same, however we will find you must think of them differently when used in hardware.

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I also want to introduce a new development board that I’ve been using, The Xess StickIt board for the XuLA. I have moved up to this board purely because it means less fiddly wires on a breakout board. It makes development much quicker for me and is an easy way to show how VHDL works. Towards the end of this article I’ll show the board and VHDL in more detail.

The VHDL structures we will look at now will all be inside a VHDL structure called a ‘process.’ The best way to think of these is to think of them as small blocks of logic. They allow VHDL to break up what you are trying to archive into manageable elements. So let’s look at the example below that has an IF statement inside it.

Looking first at the IF statement, we can see it’s written a little like a cross between C and BASIC. The first line has a logical comparison or test as with all IF statements. Here we are looking for the value of PB1 to equal 1. Note

that unlike C we only use a single equal sign to perform a test. The ‘then’ tells VHDL where the end of the test is and where the start of the code is. Here we can see that when PB1 equals logic 1 then two outputs (LED1,3) are turned on, and two are turned off (LED2,4).

The ‘else’ keyword is used to show us what code will be performed if the test returns not true and the ‘end if’ shows the end of the ‘IF’ section. As you can see, the method of use for an ‘IF’ statement is the same as in software languages with just a twist on the syntax used.

Our IF statement is, however, wrapped by a ‘process.’ This process allows for a few things to be done but here we are only interested in what is called the ‘sensitivity’ of the process. Following the process keyword we see that the value PB1 is listed in brackets. This tells VHDL that this signal is sensitive to how the following ‘block’ will work, effectively saying you need to perform the following if that value of PB1 changes. The process then has a ‘begin’ and

IF Statement CASE Statement

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TECH ARTICLE‘end process’ to identify the contents. This example is very simple but shows the basic structure that all examples will follow time and time again.

So the IF statement was very simple and easy. So too is the CASE statement, as the example on page 28 shows.

Here we see the same use of the process wrapping around the CASE structure. How-ever, there is a difference compared to lan-guages like C. We see that the ‘case’ key-word is used to tell VHDL which signal we are interested in. Then we see the introduction of the keyword ‘when.’ After each ‘when’ we can place the test to be applied, and the following lines are then carried out if this is true.

My example only has one test, but you could include as many as you like. If you have a programming background then you will know that in lan-guages like C we see the ‘default’ keyword used to mean “anything else.” In VHDL we can do the same by using the ‘when others’ where ‘others’ means anything else not defined above. This makes certain that all combinations are tested and ac-counted for. Later on we will see that this can make a significant difference to what logic is generated. For now, always use the ‘when others’ clause.

Both the examples above will give the same result, so you will probably ask what the differ-ence between using IF or CASE statements is?

IF statements can allow for multiple signals or conditions to be tested. It’s also possible for the ‘elsif’ (Note that it’s not written “else if”) to be used to test a different signal test combi-nation if the first is not true. IF statements can be quite complex in their use. However the CASE statement is restrictive to one signal and one signal value that is tested. In this form, a CASE statement is much easier to read and to code than a long list of IF statements and is typically the only choice when designing state machines, for example. You can see that

both IF and CASE statements have their own pros and cons, despite their similar functions.

Let’s not look at the difference I have made in the physical hardware. As I said, it can be confusing to have buttons wired up to give a logic zero when pressed. Because

that is the case, we used the NOT function to invert the incoming signal. My new development board

allows for the easy connection of either PMOD or WING add-on boards. Both of these are very

popular as a way of adding LEDs, buttons, or other devices to a base develop-

ment board. In this article, I decided to use the button add-on board from Papilio. Papilio, like our ex-amples before, has four buttons and four LEDs.

My first change was to update the .ucf file used to tell our software which

pins are connected to what. Xess supply a standard .ucf file for use with the XuLA FPGA

board, but when using the newer XuLA2 the pin identifications are different. Because they are

different, I used the free Xess tool to convert the pin mappings over. I also decided at the same time to name

our inputs so they match those on the Papilio board. That is why we now have PB1 to 4 (PB meaning Push Button) in place of

colored button names. Moving the pin assignments around was very easy and one of the great things about FPGA design. ■

The best way to think of VHDL structures is to think of them as small blocks of logic. They allow VHDL to break up what you are trying to archive into

manageable elements.

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