Q&A: Scott Garman, Technical Evangelist

Scott Garman is more than just a Linux software engineer. He is also heavily involved with the Yocto Project, an open-source collaboration that provides tools for the embedded Linux industry. In 2013, Scott helped Intel launch the MinnowBoard, the company’s first open-hardware SBC. —Nan Price, Associate Editor

Scott Garman

Scott Garman

NAN: Describe your current position at Intel. What types of projects have you developed?

SCOTT: I’ve worked at Intel’s Open Source Technology Center for just about four years. I began as an embedded Linux software engineer working on the Yocto Project and within the last year, I moved into a technical evangelism role representing Intel’s involvement with the MinnowBoard.

Before working at Intel, my background was in developing audio products based on embedded Linux for both consumer and industrial markets. I also started my career as a Linux system administrator in academic computing for a particle physics group.

Scott was involved with an Intel MinnowBoard robotics and computer vision demo, which took place at LinuxCon Japan in May 2013.

Scott was involved with an Intel MinnowBoard robotics and computer vision demo, which took place at LinuxCon Japan in May 2013.

I’m definitely a generalist when it comes to working with Linux. I tend to bounce around between things that don’t always get the attention they need, whether it is security, developer training, or community outreach.

More specifically, I’ve developed and maintained parallel computing clusters, created sound-level management systems used at concert stadiums, worked on multi-room home audio media servers and touchscreen control systems, dug into the dark areas of the Autotools and embedded Linux build systems, and developed fun conference demos involving robotics and computer vision. I feel very fortunate to be involved with embedded Linux at this point in history—these are very exciting times!

Scott is shown working on an Intel MinnowBoard demo, which was built around an OWI Robotic Arm.

Scott is shown working on an Intel MinnowBoard demo, which was built around an OWI Robotic Arm.

NAN: Can you tell us a little more about your involvement with the Yocto Project (www.yoctoproject.org)?

SCOTT: The Yocto Project is an effort to reduce the amount of fragmentation in the embedded Linux industry. It is centered on the OpenEmbedded build system, which offers a tremendous amount of flexibility in how you can create embedded Linux distros. It gives you the ability to customize nearly every policy of your embedded Linux system, such as which compiler optimizations you want or which binary package format you need to use. Its killer feature is a layer-based architecture that makes it easy to reuse your code to develop embedded applications that can run on multiple hardware platforms by just swapping out the board support package (BSP) layer and issuing a rebuild command.

New releases of the build system come out twice a year, in April and October.

Here, the OWI Robotic Arm is being assembled.

Here, the OWI Robotic Arm is being assembled.

I’ve maintained various user space recipes (i.e., software components) within OpenEmbedded (e.g., sudo, openssh, etc.). I’ve also made various improvements to our emulation environment, which enables you to run QEMU and test your Linux images without having to install it on hardware.

I created the first version of a security tracking system to monitor Common Vulnerabilities and Exposures (CVE) reports that are relevant to recipes we maintain. I also developed training materials for new developers getting started with the Yocto Project, including a very popular introductory screencast “Getting Started with the Yocto Project—New Developer Screencast Tutorial

NAN: Intel recently introduced the MinnowBoard SBC. Describe the board’s components and uses.

SCOTT: The MinnowBoard is based on Intel’s Queens Bay platform, which pairs a Tunnel Creek Atom CPU (the E640 running at 1 GHz) with the Topcliff Platform controller hub. The board has 1 GB of RAM and includes PCI Express, which powers our SATA disk support and gigabit Ethernet. It’s an SBC that’s well suited for embedded applications that can use that extra CPU and especially I/O performance.

Scott doesn’t have a dedicated workbench or garage. He says he tends to just clear off his desk, lay down some cardboard, and work on things such as the Trippy RGB Waves Kit, which is shown.

Scott doesn’t have a dedicated workbench or garage. He says he tends to just clear off his desk, lay down some cardboard, and work on things such as the Trippy RGB Waves Kit, which is shown.

The MinnowBoard also has the embedded bus standards you’d expect, including GPIO, I2C, SPI, and even CAN (used in automotive applications) support. We have an expansion connector on the board where we route these buses, as well as two lanes of PCI Express for custom high-speed I/O expansion.

There are countless things you can do with MinnowBoard, but I’ve found it is especially well suited for projects where you want to combine embedded hardware with computing applications that benefit from higher performance (e.g., robots that use computer vision, as a central hub for home automation projects, networked video streaming appliances, etc.).

And of course it’s open hardware, which means the schematics, Gerber files, and other design files are available under a Creative Commons license. This makes it attractive for companies that want to customize the board for a commercial product; educational environments, where students can learn how boards like this are designed; or for those who want an open environment to interface their hardware projects.

I created a MinnowBoard embedded Linux board demo involving an OWI Robotic Arm. You can watch a YouTube video to see how it works.

NAN: What compelled Intel to make the MinnowBoard open hardware?

SCOTT: The main motivation for the MinnowBoard was to create an affordable Atom-based development platform for the Yocto Project. We also felt it was a great opportunity to try to release the board’s design as open hardware. It was exciting to be part of this, because the MinnowBoard is the first Atom-based embedded board to be released as open hardware and reach the market in volume.

Open hardware enables our customers to take the design and build on it in ways we couldn’t anticipate. It’s a concept that is gaining traction within Intel, as can be seen with the announcement of Intel’s open-hardware Galileo project.

NAN: What types of personal projects are you working on?

SCOTT: I’ve recently gone on an electronics kit-building binge. Just getting some practice again with my soldering iron with a well-paced project is a meditative and restorative activity for me.

Scott’s Blinky POV Kit is shown. “I don’t know what I’d do without my PanaVise Jr. [vise] and some alligator clips,” he said.

Scott’s Blinky POV Kit is shown. “I don’t know what I’d do without my PanaVise Jr. [vise] and some alligator clips,” he said.

I worked on one project, the Trippy RGB Waves Kit, which includes an RGB LED and is controlled by a microcontroller. It also has an IR sensor that is intended to detect when you wave your hand over it. This can be used to trigger some behavior of the RGB LED (e.g., cycling the colors). Another project, the Blinky POV Kit, is a row of LEDs that can be programmed to create simple text or logos when you wave the device around, using image persistence.

Below is a completed JeeNode v6 Kit Scott built one weekend.

Below is a completed JeeNode v6 Kit Scott built one weekend.

My current project is to add some wireless sensors around my home, including temperature sensors and a homebrew security system to monitor when doors get opened using 915-MHz JeeNodes. The JeeNode is a microcontroller paired with a low-power RF transceiver, which is useful for home-automation projects and sensor networks. Of course the central server for collating and reporting sensor data will be a MinnowBoard.

NAN: Tell us about your involvement in the Portland, OR, open-source developer community.

SCOTT: Portland has an amazing community of open-source developers. There is an especially strong community of web application developers, but more people are hacking on hardware nowadays, too. It’s a very social community and we have multiple nights per week where you can show up at a bar and hack on things with people.

This photo was taken in the Open Source Bridge hacker lounge, where people socialize and collaborate on projects. Here someone brought a brainwave-control game. The players are wearing electroencephalography (EEG) readers, which are strapped to their heads. The goal of the game is to use biofeedback to move the floating ball to your opponent’s side of the board.

This photo was taken in the Open Source Bridge hacker lounge, where people socialize and collaborate on projects. Here someone brought a brainwave-control game. The players are wearing electroencephalography (EEG) readers, which are strapped to their heads. The goal of the game is to use biofeedback to move the floating ball to your opponent’s side of the board.

I’d say it’s a novelty if I wasn’t so used to it already—walking into a bar or coffee shop and joining a cluster of friendly people, all with their laptops open. We have coworking spaces, such as Collective Agency, and hackerspaces, such as BrainSilo and Flux (a hackerspace focused on creating a welcoming space for women).

Take a look at Calagator to catch a glimpse of all the open-source and entrepreneurial activity going on in Portland. There are often multiple events going on every night of the week. Calagator itself is a Ruby on Rails application that was frequently developed at the bar gatherings I referred to earlier. We also have technical conferences ranging from the professional OSCON to the more grassroots and intimate Open Source Bridge.

I would unequivocally state that moving to Portland was one of the best things I did for developing a career working with open-source technologies, and in my case, on open-source projects.

Arduino MOSFET-Based Power Switch

Circuit Cellar columnist Ed Nisley has used Arduino SBCs in many projects over the years. He has found them perfect for one-off designs and prototypes, since the board’s all-in-one layout includes a micrcontroller with USB connectivity, simple connectors, and a power regulator.

But the standard Arduino presents some design limitations.

“The on-board regulator can be either a blessing or a curse, depending on the application. Although the board will run from an unregulated supply and you can power additional circuitry from the regulator, the minute PCB heatsink drastically limits the available current,” Nisley says. “Worse, putting the microcontroller into one of its sleep modes doesn’t shut off the rest of the Arduino PCB or your added circuits, so a standard Arduino board isn’t suitable for battery-powered applications.”

In Circuit Cellar’s January issue, Nisley presents a MOSFET-based power switch that addresses such concerns. He also refers to one of his own projects where it would be helpful.

“The low-resistance Hall effect current sensor that I described in my November 2013 column should be useful in a bright bicycle taillight, but only if there’s a way to turn everything off after the ride without flipping a mechanical switch…,” Nisley says. “Of course, I could build a custom microcontroller circuit, but it’s much easier to drop an Arduino Pro Mini board atop the more interesting analog circuitry.”

Nisley’s January article describes “a simple MOSFET-based power switch that turns on with a push button and turns off under program control: the Arduino can shut itself off and reduce the battery drain to nearly zero.”

Readers should find the article’s information and circuitry design helpful in other applications requiring automatic shutoff, “even if they’re not running from battery power,” Nisley says.

Figure 1: This SPICE simulation models a power p-MOSFET with a logic-level gate controlling the current from the battery to C1 and R2, which simulate a 500-mA load that is far below Q2’s rating. S1, a voltage-controlled switch, mimics an ordinary push button. Q1 isolates the Arduino digital output pin from the raw battery voltage.

Figure 1: This SPICE simulation models a power p-MOSFET with a logic-level gate controlling the current from the battery to C1 and R2, which simulate a 500-mA load that is far below Q2’s rating. S1, a voltage-controlled switch, mimics an ordinary push button. Q1 isolates the Arduino digital output pin from the raw battery voltage.

The article takes readers from SPICE modeling of the circuitry (see Figure 1) through developing a schematic and building a hardware prototype.

“The PCB in Photo 1 combines the p-MOSFET power switch from Figure 2 with a Hall effect current sensor, a pair of PWM-controlled n-MOFSETs, and an Arduino Pro Mini into

The power switch components occupy the upper left corner of the PCB, with the Hall effect current sensor near the middle and the Arduino Pro Mini board to the upper right. The 3-D printed red frame stiffens the circuit board during construction.

Photo 1: The power switch components occupy the upper left corner of the PCB, with the Hall effect current sensor near the middle and the Arduino Pro Mini board to the upper right. The 3-D printed red frame stiffens the circuit board during construction.

a brassboard layout,” Nisley says. “It’s one step beyond the breadboard hairball I showed in my article “Low-Loss Hall Effect Current Sensing” (Circuit Cellar 280, 2013), and will help verify that all the components operate properly on a real circuit board with a good layout.”

For much more detail about the verification process, PCB design, Arduino interface, and more, download the January issue.

The actual circuit schematic includes the same parts as the SPICE schematic, plus the assortment of connectors and jumpers required to actually build the PCB shown in Photo 1.

Figure 2: The actual circuit schematic includes the same parts as the SPICE schematic, as well as the assortment of connectors and jumpers required to actually build the PCB shown in Photo 1.

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A Look at Low-Noise Amplifiers

Maurizio Di Paolo Emilio, who has a PhD in Physics, is an Italian telecommunications engineer who works mainly as a software developer with a focus on data acquisition systems. Emilio has authored articles about electronic designs, data acquisition systems, power supplies, and photovoltaic systems. In this article, he provides an overview of what is generally available in low-noise amplifiers (LNAs) and some of the applications.

By Maurizio Di Paolo Emilio
An LNA, or preamplifier, is an electronic amplifier used to amplify sometimes very weak signals. To minimize signal power loss, it is usually located close to the signal source (antenna or sensor). An LNA is ideal for many applications including low-temperature measurements, optical detection, and audio engineering. This article presents LNA systems and ICs.

Signal amplifiers are electronic devices that can amplify a relatively small signal from a sensor (e.g., temperature sensors and magnetic-field sensors). The parameters that describe an amplifier’s quality are:

  • Gain: The ratio between output and input power or amplitude, usually measured in decibels
  • Bandwidth: The range of frequencies in which the amplifier works correctly
  • Noise: The noise level introduced in the amplification process
  • Slew rate: The maximum rate of voltage change per unit of time
  • Overshoot: The tendency of the output to swing beyond its final value before settling down

Feedback amplifiers combine the output and input so a negative feedback opposes the original signal (see Figure 1). Feedback in amplifiers provides better performance. In particular, it increases amplification stability, reduces distortion, and increases the amplifier’s bandwidth.

 Figure 1: A feedback amplifier model is shown here.


Figure 1: A feedback amplifier model is shown.

A preamplifier amplifies an analog signal, generally in the stage that precedes a higher-power amplifier.

IC LOW-NOISE PREAMPLIFIERS
Op-amps are widely used as AC amplifiers. Linear Technology’s LT1028 or LT1128 and Analog Devices’s ADA4898 or AD8597 are especially suitable ultra-low-noise amplifiers. The LT1128 is an ultra-low-noise, high-speed op-amp. Its main characteristics are:

  • Noise voltage: 0.85 nV/√Hz at 1 kHz
  • Bandwidth: 13 MHz
  • Slew rate: 5 V/µs
  • Offset voltage: 40 µV

Both the Linear Technology and Analog Devices amplifiers have voltage noise density at 1 kHz at around 1 nV/√Hz  and also offer excellent DC precision. Texas Instruments (TI)  offers some very low-noise amplifiers. They include the OPA211, which has 1.1 nV/√Hz  noise density at a  3.6 mA from 5 V supply current and the LME49990, which has very low distortion. Maxim Integrated offers the MAX9632 with noise below 1nV/√Hz.

The op-amp can be realized with a bipolar junction transistor (BJT), as in the case of the LT1128, or a MOSFET, which works at higher frequencies and with a higher input impedance and a lower energy consumption. The differential structure is used in applications where it is necessary to eliminate the undesired common components to the two inputs. Because of this, low-frequency and DC common-mode signals (e.g., thermal drift) are eliminated at the output. A differential gain can be defined as (Ad = A2 – A1) and a common-mode gain can be defined as (Ac = A1 + A2 = 2).

An important parameter is the common-mode rejection ratio (CMRR), which is the ratio of common-mode gain to the differential-mode gain. This parameter is used to measure the  differential amplifier’s performance.

Figure 2: The design of a simple preamplifier is shown. Its main components are the Linear Technology LT112 and the Interfet IF3602 junction field-effect transistor (JFET).

Figure 2: The design of a simple preamplifier is shown. Its main components are the Linear Technology LT1128 and the Interfet IF3602 junction field-effect transistor (JFET).

Figure 2 shows a simple preamplifier’s design with 0.8 nV/√Hz at 1 kHz background noise. Its main components are the LT1128 and the Interfet IF3602 junction field-effect transistor (JFET).  The IF3602 is a dual N-channel JFET used as stage for the op-amp’s input. Figure 3 shows the gain and Figure 4 shows the noise response.

Figure 3: The gain of a low-noise preamplifier.

Figure 3: The is a low-noise preamplifier’s gain.

 

Figure 4: The noise response of a low-noise preamplifier

Figure 4: A low-noise preamplifier’s noise response is shown.

LOW NOISE PREAMPLIFIER SYSTEMS
The Stanford Research Systems SR560 low-noise voltage preamplifier has a differential front end with 4nV/√Hz input noise and a 100-MΩ input impedance (see Photo 1a). Input offset nulling is accomplished by a front-panel potentiometer, which is accessible with a small screwdriver. In addition to the signal inputs, a rear-panel TTL blanking input enables you to quickly turn the instrument’s gain on and off (see Photo 1b).

Photo 1a:The Stanford Research Systems SR560 low-noise voltage preamplifier

Photo 1a: The Stanford Research Systems SR560 low-noise voltage preamplifier. (Photo courtesy of Stanford Research Systems)

Photo 1 b: A rear-panel TTL blanking input enables you to quickly turn the Stanford Research Systems SR560 gain on and off.

Photo 1b: A rear-panel TTL blanking input enables you to quickly turn the Stanford Research Systems SR560 gain on and off. (Photo courtesy of Stanford Research Systems)

The Picotest J2180A low-noise preamplifier provides a fixed 20-dB gain while converting a 1-MΩ input impedance to a 50-Ω output impedance and 0.1-Hz to 100-MHz bandwidth (see Photo 2). The preamplifier is used to improve the sensitivity of oscilloscopes, network analyzers, and spectrum analyzers while reducing the effective noise floor and spurious response.

Photo 2: The Picotest J2180A low-noise preamplifier is shown.

Photo 2: The Picotest J2180A low-noise preamplifier is shown. (Photo courtesy of picotest.com)

Signal Recovery’s Model 5113 is among the best low-noise preamplifier systems. Its principal characteristics are:

  • Single-ended or differential input modes
  • DC to 1-MHz frequency response
  • Optional low-pass, band-pass, or high-pass signal channel filtering
  • Sleep mode to eliminate digital noise
  • Optically isolated RS-232 control interface
  • Battery or line power

The 5113 (see Photo 3 and Figure 5) is used in applications as diverse as radio astronomy, audiometry, test and measurement, process control, and general-purpose signal amplification. It’s also ideally suited to work with a range of lock-in amplifiers.

Photo 3: This is the Signal Recovery Model 5113 low-noise pre-amplifier.

Photo 3: This is the Signal Recovery Model 5113 low-noise preamplifier. (Photo courtesy of Signal Recovery)

Figure 5: Noise contour figures are shown for the Signal Recovery Model 5113.

Figure 5: Noise contour figures are shown for the Signal Recovery Model 5113.

WRAPPING UP
This article briefly introduced low-noise amplifiers, in particular IC system designs utilized in simple or more complex systems such as the Signal Recovery Model 5113, which is a classic amplifier able to obtain different frequency bands with relative gain. A similar device is the SR560, which is a high-performance, low-noise preamplifier that is ideal for a wide variety of applications including low-temperature measurements, optical detection, and audio engineering.

Moreover, the Krohn-Hite custom Models 7000 and 7008 low-noise differential preamplifiers provide a high gain amplification to 1 MHz with an AC output derived from a very-low-noise FET instrumentation amplifier.

One common LNA amplifier is a satellite communications system. The ground station receiving antenna will connect to an LNA, which is needed because the received signal is weak. The received signal is usually a little above background noise. Satellites have limited power, so they use low-power transmitters.

Telecommunications engineer Maurizio Di Paolo Emilio was born in Pescara, Italy. Working mainly as a software developer with a focus on data acquisition systems, he helped design the thermal compensation system (TCS) for the optical system used in the Virgo Experiment (an experiment for detecting gravitational waves). Maurizio currently collaborates with researchers at the University of L’Aquila on X-ray technology. He also develops data acquisition hardware and software for industrial applications and manages technical training courses. To learn more about Maurizio and his expertise, read his essay on “The Future of Data Acquisition Technology.”

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