Control and Comms Solutions Enhance Drone Designs

Synched in the Sky

There’s no slowing down the pace of commercial drone innovation. Helping system developers keep pace, technology vendors provide a wide range of communications and control products to improve the capabilities of both drone designs and the infrastructure supporting drones.

By Jeff Child, Editor-in-Chief

Commercial drones continue be among the most dynamic segments of embedded system design today. The sophistication of commercial/civilian drone technologies are advancing faster than most people could have imagined just a few years ago. Feeding those needs, chip, module and software vendors of all sizes have been creating new solutions to help drone system developers create new drone products and get to market quickly.

While drone technology encompasses several areas—from processing to video to power—here we’re focusing on communication and control solutions for drone system designs. Commercial drones rely on advanced wireless communications technologies for both control and for streaming captured video from drone-based cameras. Meanwhile, a variety of solutions have emerged for aspects of drone control, such as autonomous flight management and IoT-style integration of drones into powerful IoT networks.

Small Size, Long Range

Datalink modules are an important technology for drone communication. It’s a tricky mix to be able to provide long-range communication with a drone, and still keep it to a small solution that’s easy to embed on a commercial drone. With just that in mind, Airborne Innovations offers its Picoradio OEM, the company’s latest miniature OEM product based on the pDDL (Digital Data Link) from Microhard Systems. The board is a full-featured pico-miniature advanced datalink module geared at demanding miniature long range drone applications (Figure 1).

Figure 1
The Picoradio OEM board is a full-featured pico-miniature advanced datalink module geared for demanding miniature, long-range drone applications.

With the Picoradio advanced single link system, you can perform three functions in one: HD video capable data rates, autopilot command/control and manual control with the company’s add-on SBUS passthrough module. Delivering a high-power, long-range broadband COFDM link, the board provides a variety of features in a tiny 17.6 g board that measures 40 mm × 40 mm × 10 mm.

Picoradio OEM’s 1 W COFDM RF output has a typical range of 5 miles with very basic antennas—much longer range is possible using high gain antennas, RF amplifiers, tracking antennas and so on. Output power is software selectable from 7 dBm to 30 dBm in 1 dBm steps. The dual Ethernet ports can be used as Ethernet bridge ports or separate LAN segments. Two transparent serial ports are provided—one is switchable RS-232/3.3V TTL, one is TTL only.

The board features wide input range efficient buck-boost operation. Inputs of 8  V to 58 V is supported at full output power, and 5 V to 58 V with limitations. Auxiliary power output is 12 V at 2 A typical or up to 12 V at 5 A (with input voltage limitations). These specs make it capable of powering cameras, gimbals and so on from wide input range battery power. Power-over-Ethernet (PoE) is possible using separate power and data lines.

According to the company, the first revision of this board was highly successful and functional. The new version uses the 2.4 GHz unlicensed band at up to 1 W RF output. This is not a Wi-Fi radio, but rather uses a superior Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation which is optimized for drone use. The default version has no encryption, and it can be exported outside the US. 128-bit encryption is available for some customers but has export restrictions. 256-bit encryption is available to domestic users.

Digital Data Link

Aside from the one used in Airborne Innovations’ board, Microhard Systems offers a variety of DDL solutions. Among its newest of these products is its pMDDL5824 module, a dual-frequency 5.8 GHz and 2.4 GHz MIMO(2X2) digital data link. The module is a miniature OEM, high power, 2X2 MIMO wireless OEM solution (Figure 2). This dual- frequency solution allows software selectable operation in the 2.4 GHz or 5 GHz frequency bands. The DDL uses maximal ratio combining (MRC), maximal likelihood (ML) decoding and low-density parity check (LDPC) to achieve robust RF performance.

Figure 2
The pMDDL5824 module is a dual- frequency 5.8 GHz and 2.4 GHz MIMO(2X2) digital data link in a miniature, wireless OEM module solution.

According to the company, the miniature, lightweight and robust design allows the pMDDL5824 to be well suited for size sensitive applications like commercial drones. The high-speed, long-range capabilities of the pMDDL5824 allow for high-quality wireless video and telemetry communications. The device provides up to 25 Mbps IPERF throughput at 8 MHz channel (-78 dBm) and up to 2 Mbps IPERF throughput at 8 MHz channel ( -102 dBm). It provides dual 10/100 Ethernet Ports (LAN/WAN) and supports point-to-point, point-to-multipoint and mesh (future) networks. It has Master, Remote and Relay operating modes and an adjustable total transmit power (up to 1 W). Interfacing to the unit can be done through local console, telnet and by web browser.

Video Modem for Drones

It goes without saying that one the most common forms of data that drones need to transmit is video captured by the drone. The company Amimon has solutions to provide here. As a developer and provider of ICs and complete solutions for the wireless High-Definition audio-video market, they target markets beyond just drones, but its technology is very well suited for drones.

According to the company, its video modem solution utilizes both MIMO and OFDM technologies, combined with Joint Source Channel Coding (JSCC) capability to transmit Full-HD 1080p60 video resolution over a bandwidth of 40 MHz or 20 MHz. Amimon’s latest 3rd generation baseband ICs allow for the delivery of 4K wireless video in high quality, while still maintaining zero latency (<1 ms) capabilities.

The multiple inputs and multiple outputs, or MIMO, is the term used for multiple antennas at both the transmitter and receiver to improve communication bandwidth and performance. MIMO technology offers a significant increase in data throughput and link robustness without additional bandwidth or increased transmit power. It achieves this by spreading the same total transmit power over the antennas to achieve an array gain that improves the spectral efficiency—more bits per second per hertz of bandwidth—or to achieve a diversity gain that improves the link reliability (reduced fading). Because of these properties, MIMO is an important part of modern wireless communication standards, such as 4G, 3GPP Long Term Evolution (LTE) and WiMAX.

Traditional wireless video compression systems use source-channel separation method, which leads to modular system design allowing independent optimization of source and channel coders. For its part, Amimon uses Joint-Source-Channel-Coding or JSCC approach. This approach enables a far better utilization of the channel capacity and handles better channel interference. Traditional systems transmit packetized information at a rate that is below the worst-case channel capacity to avoid high bit error rate (BER) and frequent retry operations. The traditional communication methods using H.264 or H.265 compression are prone to errors and thus uses buffering to ensure retransition of data when the BER exceed a certain level. They also use error correction overhead equality applied to all the transmitted bits unrelated to their visual importance. The use of JSCC eliminates these limitations.

Figure 3
Amimon’s CONNEX product line includes a variety of wireless link products. Shown here is CONNEX Mini.

Amimon productizes its video modem technology in several ways, including its CONNEX line of wireless video modems for the drone market (Figure 3). Its embedded solution is called CONNEX Embedded, designed to enable drome system designers to embed a wireless HD link into their systems with simple integration effort. The CONNEX Embedded provides a small-size, low-weight transmitter that can reach varied ranges and can be configured based on application needs. The unit is available in different configurations enabling uncompressed HD video with zero delay, Data Down/Uplink for control, standard HDMI output interfaces, SDK for controlling the link parameters and software management tools for users and operators.

Drone Control App

Just as the computing inside drones has grown more sophisticated, so too have the methods used to remote control commercial drones. An example along those lines is the Pilot app made by DroneSense. Pilot lets users control their drone using a tablet. Users can download ground control station software directly onto a tablet and then plug the tablet into the drone remote and begin flying manually, or pre-plan autonomous flights for an upcoming mission.

Users can use Pliot’s autonomous flight planning functions to create a low-altitude orbit or undertake 2D/3D mapping (Figure 4). The can fly the drone fly manually to achieve a variety of tactical objectives, all while having a complete view of telemetry, video feeds and other relevant flight data. The app’s mapping engine enables drone pilots to clearly visualize all drones collaborating in an operation, helping to prevent redundancies or collisions. They can use chat functionality to enhance communications. It lets users view multiple live video feeds of various types, including thermal.

Figure 4
The Pilot app lets users control their drone using a tablet. Users can use the app’s autonomous flight planning functions to create a low-altitude orbit or undertake 2D/3D mapping.

Another feature of Pilot is that it is drone agnostic. Users can train once on the Pilot app, and use it on whatever drone is best-suited to each mission. Whether it is a fixed-wing or a quadcopter, the pilot interface remains the same—no additional training is required for different types or brands of drones. Users can just pick the drone and sensor required to accomplish their goals and fly. No hardware configuration required.
Users of the Pilot app can upload customized checklists from DroneSense’s AirBase software into the Pilot app, ensuring pilots follow established pre-flight procedures.

Users can create and implement post-flight checklists, such as proper handling of any captured media. It allows you to enforce compliance with user policies and procedures, thereby minimizing risk and making sure assets are always handled properly. The Pilot app lets users bring in feeds from various sensor packages, such as a thermal imager, and see the output directly in the app. They can collect and view the data in the Pilot app (and DroneSense’s OpsCenter) from numerous sources for even greater situational awareness. The app’s flexible architecture allows for integration with third-party systems that may exist in a user’s organization.

Drones as IOT Edge Nodes

In many ways a commercial drone can be thought of as an IoT device. IoT implementations are comprised of edge devices with sensors, a cloud infrastructure and some sort of network or gateway linkng the edge with the cloud. SlantRange, a specialist in remote sensing and analytics systems for agriculture, made just such a drone-IoT connection in October with a new partnership with Microsoft. The deal combines Microsoft’s latest IoT connectivity and cloud analytics with SlantRange’s edge-computing capabilities into an integrated product offering for implementation developers operating large-scale drone programs in agriculture.

SlantRange has patented technologies for aerial crop inspections and introduced analytical methods that deliver valuable agronomic data within minutes of collection, anywhere in the world, using low-power edge-computing devices. Microsoft’s Azure IoT Edge is a fully managed service that delivers cloud intelligence locally by deploying and running artificial intelligence (AI), Azure services and custom logic directly on cross-platform IoT devices.

Figure 5
Through the addition of Azure IoT Edge, SlantRange’s platform provides a secure, scalable and fully integrated solution to deploy new cloud computing capabilities on top of SlantRange’s existing edge-computing architecture.

SlantRange’s current products can do data analytics conducted completely offline, without the need for an Internet connection. Through the addition of Azure IoT Edge, the new platform provides a secure, scalable and fully integrated solution to deploy new cloud-computing capabilities on top of SlantRange’s existing edge-computing architecture (Figure 5). Their edge-based solutions can now be complimented by cloud-based services to seamlessly ingest, manage and analyze data from large networks of distributed sensors. Custom analytics as well as automated machine learning and artificial intelligence algorithms can be deployed both in the cloud and at the edge to create new data insights for a variety of stakeholders within an agriculture enterprise.

SDK for Drone Control

The giant chip manufacturer Qualcomm has a foothold in the drone market on both the developer side and the end product side. For drone control, the company offers its Qualcomm Navigator software development kit (SDK). Qualcomm Navigator is an autonomous, vision-supported flight controller SDK with related modules and tools. It features multiple different flight modes with varying levels of sophistication, it is engineered to provide stable and aggressive flight for a host of applications. It includes several built-in sensor calibration procedures as well as automatic flight logging and real-time introspection tools along with post-processing, log parsing capabilities.

The SDK supports various flight modes, from manual (for expert pilots) to assisted modes (for novice pilots). The tool fuses the machine vision SDK’s VISLAM for stable flight and DFS for visual obstacle avoidance. Meanwhile, Wi-Fi-based flight control can be done using the drone controller app. The SDK enables C API’s to get telemetry and control the flight path.

Navigator is comprised of multiple libraries, executables and configuration files. The core flight controller runs on the aDSP, and other components run on the applications processor and GPU. Navigator provides a low-level C API for applications to interact with the flight controller. Supported interactions include accessing telemetry data such as battery voltage, status of sensors and current flight mode. It also supports sending remote control (RC)-style or velocity-style commands to the flight controller. With Navigator you can also send RPM or PWM commands directly to the ESCs and initiate sensor calibration procedures.

Complete Drone Solution

Most of the leading microcontroller vendors market their technologies toward drone designs in some way or another. Among the more direct of these efforts is from Infineon Technologies, offering development kits and design resources. The company provides a complete system solution that includes all essential semiconductors for drones. These Infineon products include its AURIX and XMC controllers, its iMotion motor controller, its IMU (inertial measurement units) and its XENSIV sensors line that includes pressure, radar, magnetic sensors and more.

Figure 6
This complete multicopter XMC4500 demoboard is built around an Infineon XMC4500 Arm CortexM4 32-bit MCU. IR2301 drivers, low-voltage MOSFETs and the MPU9250 Invensense IMU provide the additional units that make up the drone’s electronic powertrain, motor control and flight sensing functional blocks.

Among Infineon’s drone design offerings is a complete multicopter XMC4500 demoboard (Figure 6). At the heart of the board is the flight controller, which is built around an Infineon XMC4500 Arm CortexM4 32-bit MCU. IR2301 drivers, low-voltage MOSFETs and the MPU9250 Invensense IMU provide the additional units that make up the electronic powertrain, motor control and flight sensing functional blocks.

There’s no doubt that today’s quad-copter- style commercial drones wouldn’t be possible without today’s high levels of chip integration. But even as developers push for more autonomous operations and AI aboard drones, they will also be need to send and receive control and video data to and from drones. Embedded control and communication technologies will continue to play a major role is these efforts. Later this year, in July, Circuit Cellar will take a closer look at the video and embedded camera sides of drone system design.

Airborne Innovations | www.airborneinnovations.com

Amimon | www.amimon.com

DroneSense | www.dronesense.com

Infineon Technologies | www.infineon.com

SlantRange | www.slantrange.com

Qualcomm Technologies | www.qualcomm.com

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Module Combines Isolated Data Comms and Power in One Device

Murata Power Solutions has announced the introduction of the NMUSB2022PMC, a surface mount powered data isolator module that conveniently provides dual port USB data and power isolation from a single upstream port. When used in conjunction with a USB host, a single NMUSB202PMC module counts as two USB hubs for cascaded applications and provides full 5V/500mA power to each downstream port. 250 VRMS reinforced isolation provides safety, immunity to EMI and breaking of ground loops.

The is NMUSB2022PMC is fully compliant with USB 2.0 specification, which enables hassle-free, “plug and play” operation with any USB-compatible device. It can do automatic switching between full-speed (12 Mbps) and low speed (1.5 Mbps) operation. Operating temperature ranges from -40°C to +85°C.

The device enables USB isolation function with a single SMT component. Users may power any USB compatible device from the NMUSB module. The data isolation function included with the DC-DC module adds value and convenience to the user and also eases system approval for medical systems safety certifications. Applications include industrial control for isolating sensors and medical environments, where USB is becoming common for low cost sensing and communication but isolation is necessary for safety and noise immunity. It is also well suited for harsh environment data communication and sensor communications.

Murata Power Solutions | www.murata-ps.com

Vehicle Computer Targets Comms + Control

MEN Micro has announced the BC50R, a maintenance-free box computer that has been designed for data acquisition applications in rugged environments in vehicles such as trains, commercial vehicles, mobile machines or ships. All interfaces are implemented on rugged M12 connectors (USB, digital input and output, Gigabit Ethernet, CAN and legacy serial I/O). The housing is compliant to the IP65 protection class.

On the inside, the system offers two PCI Express Mini card slots with two SIM card slots for WLAN, GNSS or 3G/4G functionality. The necessary antenna connectors can be made available at the front panel. It is powered by an AMD Embedded G-Series APU (Accelerated Processing Unit), the T48N, running at 1.4 GHz. The use of the Embedded G-Series makes for high scalability in CPU (single/dual core) performance. The BC50R is equipped with 2 GB of DDR3 SDRAM and offers SD card and mSATA slots. The system is designed for fanless operation at temperatures from -40 to +70°C (+85°C for up to 10 minutes), its special aluminum housing with cooling fins serves as a heat sink for the internal electronics and in this way provides conduction cooling.

The BC50R supports a 24 VDC and 36 VDC nom. class S2 power supply in compliance with EN 50155 or power supplies which comply with ISO 7637-2 (E-mark for automotive) (nominal input voltage 24 V) or with EN 60945 (ship). The power can be switched on and off using an ignition signal on the power connector, and a shutdown-delay time after switching off the power can be adjusted by software.

The combination of the various CPU/GPU options with the available selection of external interfaces (realized via separate graphics and I/O interface boards within the system) makes for an flexible system design that can quickly be tailored to a wide variety of applications.

MEN Micro | www.menmicro.com

Antenna Measurement Made Easy

For web Lacoste Lead Image

Covering the Basics

If you’re doing any kind of wireless communications application, that probably means including an antenna in your design. The science of antennas is complex. But here Robert shows how the task of measuring an antenna’s performance is less costly and exotic than you’d think.

By Robert Lacoste

Now that wireless communications is ubiquitous, chances are you’ll be using Bluetooth, Wi-Fi, cellular, LoRa, MiWi or other flavor of wireless interface in your next design. And that means including an antenna. Unfortunately, antenna design is not an easy topic. Even very experienced designers sometimes have had to wrestle with unexpected bad performances by their antennas. Case in point: Google “iPhone 4 antenna problem” and you will get more than 3 million web pages! In a nutshell, Apple tried to integrate a clever antenna in that model that was threaded around the phone. They didn’t anticipate that some users would put their fingers exactly where the antenna was the most sensitive to detuning. Was it a design flaw? Or a mistake by the users? It was hotly debated, but this so-called “Antennagate” probably had significant impact on Apple’s sales for a while.

I already devoted an article to antenna design and impedance matching (“The Darker Side: Antenna Basics”, Circuit Cellar 211, February 2008). Whether you include a standard antenna or design your own, you will never be sure it is working properly until you measure its actual performance. Of course, you could simply evaluate how far the system is working. But how do you go farther if the range is not enough? How do you figure out if the problem is coming from the receiver, the transmitter, propagation conditions or the antenna itself? My personal experience has been that the antenna is very often the culprit. With that in mind, it really is mandatory to measure whether or not an antenna is behaving correctly. Take a seat. This month, I will explain how to easily measure the actual performance of an antenna. You will see that the process is quite easy and that it won’t even need costly or exotic equipment.

SOME ANTENNA BASICS

Let’s start with some basics on antennas. First, all passive antennas have the same performance whether transmitting or receiving. For this article, I’ll consider the antenna as transmitting because that’s easier to measure. Let’s consider an antenna that we inject with a given radio frequency power Pconducted into its connector. Where will this power go? First off, impedance matching should be checked. If the impedance of the antenna is not well matched to the impedance of the power generator, then a part of the power will be reflected back to the generator. This will happen in particular when the transmit frequency is not equal to the resonant frequency of the antenna. In such a case, a part of Pconducted will be lost.  That is known as mismatch losses: Pavailable= Pconducted – MismatchLosses. While that itself is a very interesting subject, I have already discussed impedance matching in detail in my February 2008 article. I also devoted another article to a closely linked topic: standing waves. Standing waves appear when there is a mismatch. The article is “The Darker Side: Let’s play with standing waves” (Circuit Cellar 271, February 2013).

For the purpose of discussion here, I will for now assume that there isn’t any mismatching—and therefore no mismatch loss. …

Read the full article in the October 327 issue of Circuit Cellar

We’ve made the October 2017 issue of Circuit Cellar available as a sample issue. In it, you’ll find a rich variety of the kinds of articles and information that exemplify a typical issue of the current magazine.
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USB-to-FPGA Communications: A Case Study of the ChipWhisperer-Lite

Sending data from a computer to an FPGA is often required. This might be FPGA configuration data, register settings, or streaming data. An easy solution is to use a USB-connected microcontroller instead of a dedicated interface chip, which allows you to offload certain tasks into the microcontroller.

In Circuit Cellar 299 (June 2015), Colin O’Flynn writes:

Often your FPGA-based project will require computer communication and some housekeeping tasks. A popular solution is the use of a dedicated USB interface chip, and a soft-core processor in the FPGA for housekeeping tasks.

For an open-source hardware project I recently launched, I decided to use an external USB microcontroller instead of a dedicated interface chip. I suspect you’ll find a lot of useful design tidbits you can use for yourself—and, because it’s open source, getting details of my designs doesn’t involve industrial espionage!

The design is called the ChipWhisperer-Lite (see Photo 1). This device is a training aid for learning about side-channel power analysis of cryptographic implementations. Side-channel power analysis uses measurements of small power variations during execution of the cryptographic algorithms to break the implementation of the algorithm.

Photo 1: This shows the ChipWhisperer-Lite, which contains a Xilinx Spartan 6 LX9 FPGA and Atmel SAM3U2C microcontroller. The remaining circuitry involves the power supplies, ADC, analog processing, and a development device which the user programs with some cryptographic algorithm they are analyzing.

Photo 1: This shows the ChipWhisperer-Lite, which contains a Xilinx Spartan 6 LX9 FPGA and Atmel SAM3U2C microcontroller. The remaining circuitry involves the power supplies, ADC, analog processing, and a development device which the user programs with some cryptographic algorithm they are analyzing.

In a previous article, “Build a SoC Over Lunch” (Circuit Cellar 289, 2014), I made the case for using a soft-core processing in an FPGA. In this article I’ll play the devil’s advocate by arguing that using an external microcontroller is a better choice. Of course the truth lies somewhere in between: in this example, the requirement of having a high-speed USB interface makes an external microcontroller more cost-effective, but this won’t always be the case.

This article assumes you require computer communication as part of your design. There are many options for this. The easiest from a hardware perspective is to use a USB-Serial converter, and many projects use such a system. The downside is a fairly slow interface, and the requirement of designing a serial protocol.

A more advanced option is to use a USB adapter with a parallel interface, such as the FTDI FT2232H. These can achieve very high-speed data rates—basically up to the limit of the USB 2.0 interface. The downside of these options is that it still requires some protocol implemented on your FPGA for many applications, and it has limited extra features (such as if you need housekeeping tasks).

The solution I came to is the use of a USB microcontroller. They are widely available from most vendors with USB 2.0 high-speed (full 480 Mbps data rate) interfaces, and allow you to perform not only the USB interface, but the various housekeeping tasks that your system will require. The USB microcontroller will also likely be around the same price (or possibly cheaper) than the equivalent specialized interface chip.

When selecting a microcontroller, I recommend finding one with an external memory bus interface. This external memory bus is normally designed to allow you to map devices such as SRAM or DRAM into the memory space of the microcontroller. In our case we’ll actually be mapping FPGA registers into the microcontroller memory space, which means we don’t need any protocol for communication with the FPGA.

OflynnFig1fpga

Figure 1: This figure shows the basic connections used for memory-mapping the FPGA into the microcontroller memory space. Depending on your requirements, you can add some additional custom lines, such as a flag to indicate different FPGA register banks to use, as only a 9-bit address bus is used in this example.

I selected an Atmel SAM3U2C microcontroller, which has a USB 2.0 high-speed interface. This microcontroller is low-cost and available in TQFP package, which is convenient if you plan on hand assembling prototype boards. The connections between the FPGA and microcontroller are shown in Figure 1.

On the FPGA, it is easy to map this data bus into registers. This means that to configure some feature in the FPGA, you can just directly write into a register. Or if you are transferring data, you can read from or write to a block-RAM (BRAM) implemented in the FPGA.

Check out Colin’s ChipWhisperer-Lite KickStarter Video:

Data Communication Between “Smart” Pendants

As head of the Computer Science and Software  Engineering department at Penn State Erie, The Behrend College, Chris Coulston is busy.

But not too busy to surf the ‘Net for design inspiration.

And one of his latest projects may earn him the title of “social jewelry designer,” along with college professor and department chair.

In the June issue of Circuit Cellar, Coulston writes about his design and construction of an RGB LED pendant that “cycles through a color sequence, detects when another pendant is brought into its proximity, and communicates color sequence information to the other pendant through its LED.” The heart of the design is a Seoul Semiconductor SFT722 RGB LED.

Coulston was online a few years ago when he ran across the first half of his project inspiration—a Mitsubishi Electric Research Laboratories technical report titled “Very Low-Cost Sensing and Communication Using Bi-directional LEDs.” The report, Coulston says, “describes how an ordinary LED with no additional circuitry can act as a full-duplex communication channel.”

Pendant’s two boards

His remaining inspiration came from an article he recalled appearing in Circuit Cellar a decade ago.

The Mitsubishi labs technical report “got me thinking about Jeff Bachiochi’s article ‘Designing with RGB LEDs’ (Circuit Cellar 159, 2003), in which the challenges associated with designing a piece of LED jewelry are described,” Coulston says. “The fusion of these two ideas was the inspiration for my social jewelry design.”

Coulston’s design includes a pair of circuit boards, the upper containing the LED and analog circuitry and the lower containing the microcontroller.

“The prototype pendant is mainly controlled through a USB-to-USART bridge,” Couston says. “Its power is supplied by the same connection.”

He invites anyone who is  “curious how an LED can be used as a transceiver and how it’s used to build a piece of social jewelry” to read his article. You’ll find it in next month’s issue of Circuit Cellar.

I/O Raspberry Pi Expansion Card

The RIO is an I/O expansion card intended for use with the Raspberry Pi SBC. The card stacks on top of a Raspberry Pi to create a powerful embedded control and navigation computer in a small 20-mm × 65-mm × 85-mm footprint. The RIO is well suited for applications requiring real-world interfacing, such as robotics, industrial and home automation, and data acquisition and control.

RoboteqThe RIO adds 13 inputs that can be configured as digital inputs, 0-to-5-V analog inputs with 12-bit resolution, or pulse inputs capable of pulse width, duty cycle, or frequency capture. Eight digital outputs are provided to drive loads up to 1 A each at up to 24 V.
The RIO includes a 32-bit ARM Cortex M4 microcontroller that processes and buffers the I/O and creates a seamless communication with the Raspberry Pi. The RIO processor can be user-programmed with a simple BASIC-like programming language, enabling it to perform logic, conditioning, and other I/O processing in real time. On the Linux side, RIO comes with drivers and a function library to quickly configure and access the I/O and to exchange data with the Raspberry Pi.

The RIO features several communication interfaces, including an RS-232 serial port to connect to standard serial devices, a TTL serial port to connect to Arduino and other microcontrollers that aren’t equipped with a RS-232 transceiver, and a CAN bus interface.
The RIO is available in two versions. The RIO-BASIC costs $85 and the RIO-AHRS costs $175.

Roboteq, Inc.
www.roboteq.com

PC-Programmable Temperature Controller

Oven Industries 5R7-388 temperature controller

Oven Industries 5R7-388 temperature controller

The 5R7-388 is a bidirectional temperature controller. It can be used in independent thermoelectric modules or in conjunction with auxiliary or supplemental resistive heaters for cooling and heating applications. The solid-state MOSFET output devices’ H-bridge configuration enables the bidirectional current flow through the thermoelectric modules.
The RoHS-compliant controller is PC programmable via an RS-232 communication port, so it can directly interface with a compatible PC. It features an easily accessible communications link that enables various operational mode configurations. The 5R7-388 can perform field-selectable parameters or data acquisition in a half duplex mode.

In accordance with RS-232 interface specifications, the controller accepts a communications cable length. Once the desired set parameters are established, the PC may be disconnected and the 5R7-388 becomes a unique, stand-alone controller. All parameter settings are retained in nonvolatile memory. The 5R7-388’s additional features include 36-VDC output using split supply, a PC-configurable alarm circuit, and P, I, D, or On/Off control.

Contact Oven Industries for pricing.

Oven Industries, Inc.
www.ovenind.com

CC280: Analog Communications and Calibration

Are you an analog aficionado? You’re in luck. Two articles, in particular, focus on the November issue’s analog techniques theme. (Look for the issue shortly after mid-October, when it will be available on our website.)

Block Diagram

Data from the base adapter is sent by level shifting the RS-232 or CMOS serial data between 9 and 12 V. A voltage comparator at the remote adapter slices the signal to generate a 0-to-5-V logic signal. The voltage on the signal wire never goes low enough for the 5-V regulator to go out of regulation.

These adapters use a combination of tricks. A single pair of wires carries full-duplex serial data and a small amount of power to a remote device for tasks (e.g., continuous remote data collection and control). The digital signals can be simple on/off signals or more complex signals (e.g., RS-232).

These adapters use a combination of tricks. A single pair of wires carries full-duplex serial data and a small amount of power to a remote device for tasks (e.g., continuous remote data collection and control). The digital signals can be simple on/off signals or more complex signals (e.g., RS-232).

Dick Cappels, a consultant who tinkers with analog and mixed-signal projects, presents a design using a pair of cable adapters and simple analog circuits to enable full-duplex, bidirectional communications and power over more than 100 m of paired wires. Why bother when Power Over Ethernet  (PoE), Bluetooth, and Wi-Fi approaches are available?

“In some applications, using Ethernet is a disadvantage because of the higher costs and greater interface complexity,” Cappels says. “You can use a microcontroller that costs less than a dollar and a few analog parts described in this article to perform remote data gathering and control.”

The base unit including the 5-to-15-V power supply is simple for its functionality. The two eight-pin DIP ICs are a voltage comparator and the switching regulator.

The base unit including the 5-to-15-V power supply is simple for its functionality. The two eight-pin DIP ICs are a voltage comparator and the switching regulator.

Cappels’s need for data channels to monitor his inground water tank inspired his design. Because his local municipality did not always keep the tank filled, he needed to know when it was dry so his pumps wouldn’t run without water and possibly become damaged.
“Besides the mundane application of monitoring a water tank, the system would be excellent for other communication uses,” Cappels says, including computer connection to a home weather station and intrusion-detection systems. Bit rates up to 250 kHz also enable the system to be used in two-way voice communication such as intercoms, he says.

Retired engineer David Cass Tyler became interested in writing his series about calibration while working on a consulting project. “I came to realize that some people don’t really know how to approach the issue of taking an analog-to-digital value to actual engineering units, nor how to correct calibration factors after the fact,” Tyler says

In Part 1 of his article series, Tyler notes: “Digital inputs and digital outputs are pretty simple. They are either on or off. However, for ADCs and DACs to be accurate, they must first be calibrated. This article addresses linear ADCs and DACs.” Part 2, appearing in the December issue, will discuss using polynomial curve fitting to convert nonlinear data to real-world engineering values.

In addition to its analog-themed articles, the November issue includes topics ranging from a DIY solar array tracker’s software to power-capped computer systems.

Editor’s Note: Learn more about Circuit Cellar contributors Dick Cappels and David Cass Tyler by reading their posts about their workspaces and favorite DIY tools.

Q&A: Alenka Zajić, Communications Specialist

From building RF components for cell phones to teaching signal processing and electromagnetics at Georgia Institute of Technology’s School of Electrical and Computer Engineering, Alenka Zajić has always been interested in engineering and communications. Alenka and I discussed her fascination with a variety of communication technologies including mobile-to-mobile, computer system, energy-efficient, and wireless. She also described her current research, which focuses on improving computer communication.

Alenka Zajić

Alenka Zajić

NAN: Give us some background information. Where are you located? Where and what did you study?

ALENKA: I am originally from Belgrade, Serbia, where I got my BS and MS degrees at the School of Electrical Engineering, University of Belgrade.

After graduating with a BS degree, I was offered a design engineer job at Skyworks Solutions in Fremont, CA, where my job was to create passive RF components (e.g., antennas, filters, diplexers, baluns, etc.) for cell phones.

I was very excited to move to California, but was not sure if I would like to pursue an engineering career or a research/academic career. Since it took about six months to get an H1B visa, I decided to take all the required MS courses in Belgrade while waiting for the visa and all I had to do was finish the thesis while working in California. It was a bigger challenge than I expected, but it worked out well in the end.

While I enjoyed working in the industry, I was always more drawn to research than commercialization of products/innovations. I also enjoy “trying something new,” so it became clear to me that I should go back to school to complete my doctoral studies. Hence, I moved to Atlanta, GA, and got my PhD at the School of Electrical and Computer Engineering, Georgia Institute of Technology.

After graduation, I worked as a researcher in the Naval Research Laboratory (Washington, DC) and as a visiting assistant professor in the School of Computer Science, Georgia Tech, until last year, when I became the assistant professor at the School of Electrical and Computer Engineering, Georgia Tech.

NAN: How long have you been teaching at Georgia Tech? What courses do you currently teach and what do you enjoy most about teaching?

ALENKA: This is my second year at the School of Electrical and Computer Engineering. Last year, I taught introduction to signal processing and electromagnetics for undergraduates. This year, I am teaching electromagnetics for graduate students. One of the most rewarding aspects of university teaching is the opportunity to interact with students inside and outside of the classroom.

NAN: As an engineering professor, you have some insight into what interests future engineers. What are some “hot topics” that intrigue your students?

ALENKA: Over the years, I have seen different areas of electrical and computer engineering being “hot topics.” Currently, embedded programming is definitely popular because of the cell phone applications. Optical communications and bioengineering are also very popular.

NAN: You have contributed to several publications and industry journals, written papers for symposiums, and authored a book, Mobile-to-Mobile Wireless Channels. A central theme is mobile-to-mobile applications. Tell us what fascinates you about this topic.

ALENKA: Mobile communications are rapidly becoming the communications in most people’s minds because they provide the ability to connect people anywhere and at any time, even on the move. While present-day mobile communications systems can be classified as “fixed-to-mobile” because they enable mobility only on one end (e.g., the mobile phone) while the other end (e.g., the base station) is immobile, emerging mobile-to-mobile (M-to-M) communications systems enable mobile users or vehicles to directly communicate with each other.

The driving force behind M-to-M communications is consumer demand for better coverage and quality of service (e.g., in rural areas where base stations or access points are sparse or not present or in disaster-struck areas where the fixed infrastructure is absent), as well as increased mobility support, location-based services, and energy-efficient communication (e.g., for cars moving in opposite directions on a highway that exchange information about traffic conditions ahead, or when mobile devices “gang together” to reach a far-away base station without each of them expending a lot of power).

Although M-to-M is still a relatively young technology, it is already finding its way into wireless standards (e.g., IEEE 802.22 for cognitive radio, IEEE 802.11p for intelligent transportation systems, IEEE 802.16 for WiMAX systems, etc.).

Propagation in M-to-M wireless channels is different from traditional fixed-to-mobile channels. The quality of service, energy efficiency, mobility support, and other advantages of M-to-M communication all depend on having good models of the M-to-M propagation channels.

My research is focused on studying propagation and enabling communication in challenging environments (e.g., vehicle-to-vehicle wireless radio communications, underwater vehicle-to-underwater vehicle acoustic communications, and inside a processor chip). In each of these projects, my work aims not only to improve existing functionality, but also to provide highly useful functionality that has not existed before. Examples of such functionality include navigating people in a direction that will restore (or improve) their connection, voice, or even video between submerged vehicles (e.g., for underwater well-service operations), and use of on-chip transmission lines and antennas to achieve broadcast-type communication that is no longer feasible using traditional wires.

NAN: Your research interests include electromagnetics and computer system and wireless communications. How have your interests evolved?

ALENKA: My research was mostly focused on electromagnetics and its impact on wireless communications until I joined the School of Computer Science at Georgia Tech. Talking to my Computer Science colleagues, I have realized that some of the techniques developed for telecommunications can be modified to improve communication among processors, memory, racks in data centers, and so forth. Hence, I started investigating the problem of improving communication among computers.

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

 

Two of Alenka Zajić's currrent projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems.

Two of Alenka Zajićs currrent projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems.

ALENKA: I have several projects and they all include theoretical and experimental work. Two of my current projects are energy-efficient underwater acoustic communications and electromagnetic side channels in high-performance processors and systems. I will provide a brief explanation of each project.

Energy-efficient underwater acoustic communications: Many scientific, defense, and safety endeavors require communications between untethered submerged devices and/or vehicles.

Examples include sensor networks for seismic monitoring, analysis of resource deposits, oceanographic and environmental studies, tactical surveillance, and so forth, as well as communications between unmanned or autonomous underwater vehicles (UUVs, AUVs) for deep-water construction, repairs, scientific or resource exploration, defense applications, and so forth. Such underwater sensing and vehicular applications will require energy-efficient underwater communications, because underwater sensor networks and AUVs are highly energy-constrained. They are typically powered by batteries that are very difficult to replace or recharge deep underwater. At the same time, existing wireless communication approaches still provide extremely low data rates, work over very limited distances, and have low energy efficiency. Radio signals and wireless optics have a very limited range underwater, so underwater wireless communications mostly rely on acoustic signals that can travel long distances in water.

Some of Alenka’s research focuses on electromagnetic side channels in high-performance processors and systems. This is a measurement setup.

Some of Alenka’s research focuses on electromagnetic side channels in high-performance processors and systems. This is a measurement setup.

Unfortunately, acoustic underwater communications have a narrow available spectrum—propagation delays that are orders-of-magnitude longer than in radio communications—and many sources of signal distortion that further reduce data rates and increase the required transmitted power when using simple modulations and coding. Hence, we are working on characterization of underwater acoustic channels and their implications for underwater-vehicle-to-underwater-vehicle communications and networking.

Electromagnetic side channels in high-performance processors and systems: Security of many computer systems relies on the basic assumption that data theft through unauthorized physical tampering with the system is difficult and easily detected, even when attackers are in physical proximity to systems (e.g., desktops in cubicles, laptops and smartphones used in public spaces, remote data centers used for cloud computing, remotely operated robotic vehicles, aircraft, etc.).

On the other hand, the motivation for attackers keeps expanding. Increasing use of electronic banking provides monetary incentives for successful attacks, while the trend toward computer-controlled everything (e.g., power plants, robotic weapons, etc.) can motivate terrorists and/or rogue states.

Although simple physical attacks (e.g., stealing the system or taking it apart to insert snooping devices) are relatively hard to carry out without significant risk of detection, more sophisticated physical attacks are likely to be explored by attackers as incentives for such attacks grow. Side-channel attacks are especially worrisome, because they circumvent traditional protection measures.

Most side-channel attacks (e.g., power analysis, timing analysis, or cache-based attacks) still require some degree of direct access (i.e., to attach probes, run processes, etc.) that exposes attackers to a significant risk of detection. However, attacks that exploit electromagnetic emanations from the system only require physical proximity. So, increasingly motivated attackers may be able to carry out numerous attacks completely undetected, and several other side channels (e.g., power, timing, memory use, etc.) can “spill over” into the electromagnetic side channel, turning electromagnetic emanations into a very information-rich side channel.

My work in this domain focuses on carrying out a systematic investigation of electromagnetic side channel data leakage, quantifying the extent of the threat, and providing useful insights for computer designers to minimize such leakage.

NAN: Is there a particular electronics engineer or academic who has inspired the type of work you do today?

ALENKA: I have been fortunate to have great mentors (Dr. Antonije Djordjević and Dr. Gordon Stüber) who taught me the importance of critical thinking, asking the right questions in problem-solving, and clearly and concisely stating my ideas and results.

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

ADLINK PCIe-2602

ADLINK PCIe-2602 Video/Audio Capture Card

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

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

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

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

Contact ADLINK for pricing.

ADLINK Technology, Inc.
www.adlinktech.com

Accurate Measurement Power Analyzer

The PA4000 power analyzer provides accurate power measurements. It offers one to four input modules, built-in test modes, and standard PC interfaces.

The analyzer features innovative Spiral Shunt technology that enables you to lock onto complex signals. The Spiral Shunt design ensures stable, linear response over a range of input current levels, ambient temperatures, crest factors, and other variables. The spiral construction minimizes stray inductance (for optimum high-frequency performance) and provides high overload capability and improved thermal stability.

The PA4000’s additional features include 0.04% basic voltage and current accuracy, dual internal current shunts for optimal resolution, frequency detection algorithms for noisy waveform tracking, application-specific test modes to simplify setup. The analyzer  easily exports data to a USB flash drive or PC software. Harmonic analysis and communications ports are included as standard features.

Contact Tektronix for pricing.

Tektronix, Inc.
www.tek.com

Multiband 4G LTE-Only Modules

The TOBY-L1 series is u-blox’s latest line of ultra-compact long-term evolution (LTE) modules. The TOBY-L100 and its European version, the TOBY-L110, are suitable for tablets, mobile routers, set-top boxes, and high-speed machine-to-machine (M2M) applications (e.g., digital signage, mobile health, and security systems).

Compared with multi-mode modules, LTE-only modules offer cost advantages. Therefore, the TOBY-L1 works well in networks with advanced LTE deployment applications.

The LTE modules are available in two versions: the TOBY-L100 for the US (bands 4 and 13 for Verizon) and the TOBY-L110 for Europe (bands 3, 7, and 20 for EU operators). Contained in a compact 152-pin LGA module, the TOBY-L1 series is layout-compatible with u-blox’s SARA Global System for Mobile (GSM) and LISA Universal Mobile Telecommunications System/Code Division Multiple Access (UMTS/CDMA) module series to facilitate easy product migration and low-cost regional end-device adaptation.

The TOBY-L1 modules are based on u-blox’s LTE protocol stack. The modules support smooth migration between 2G, 3G, and 4G technologies and feature small packaging and comprehensive support tools. The TOBY-L1 LGA modules measure 2.8 mm × 24.8 mm × 35.6 mm, which enables them to easily mount on any application board.

The modules support USB 2.0 and firmware update over the air (FOTA) technology. The TOBY-L1 series delivers ultra-fast data rates and operates from –40°C to 85°C. USB drivers for Windows XP and 7 plus Radio Interface Layer (RIL) software for Android 4.0 and 4.2 are available free of charge.

Contact u-blox for pricing.

u-blox
www.u-blox.com

Embedded Wireless Made Simple

Last week at the 2013 Sensors Expo in Chicago, Anaren had interesting wireless embedded control systems on display. The message was straightforward: add an Anaren Integrated Radio (AIR) module to an embedded system and you’re ready to go wireless.

Bob Frankel demos embedded mobile control

Bob Frankel of Emmoco provided a embedded mobile control demonstration. By adding an AIR module to a light control system, he was able to use a tablet as a user interface.

The Anaren 2530 module in a light control system (Source: Anaren)

In a separate demonstration, Anaren electrical engineer Mihir Dani showed me how to achieve effective light control with an Anaren 2530 module and TI technology. The module is embedded within the light and compact remote enables him to manipulate variables such as light color and saturation.

Visit Anaren’s website for more information.

Infrared Communications for Atmel Microcontrollers

Are you planning an IR communications project? Do you need to choose a microcontroller? Check out the information Cornell University Senior Lecturer Bruce Land sent us about inexpensive IR communication with Atmel ATmega microcontrollers. It’s another example of the sort of indispensable information covered in Cornell’s excellent ECE4760 course.

Land informed us:

I designed a basic packet communication scheme using cheap remote control IR receivers and LED transmitters. The scheme supports 4800 baud transmission,
with transmitter ID and checksum. Throughput is about twenty 20-character packets/sec. The range is at least 3 meters with 99.9% packet receive and moderate (<30 mA) IR LED drive current.

On the ECE4760 project page, Land writes:

I improved Remin’s protocol by setting up the link software so that timing constraints on the IR receiver AGC were guaranteed to be met. It turns out that there are several types of IR reciever, some of which are better at short data bursts, while others are better for sustained data. I chose a Vishay TSOP34156 for its good sustained data characteristics, minimal burst timing requirements, and reasonable data rate. The system I build works solidly at 4800 baud over IR with 5 characters of overhead/packet (start token, transmitter number, 2 char checksum , end token). It works with increasing packet loss up to 9000 baud.

Here is the receiver circuit.

The receiver circuit (Source: B. Land, Cornell University ECE4760 Infrared Communications
for Atmel Mega644/1284 Microcontrollers)

Land explains:

The RC circuit acts a low-pass filter on the power to surpress spike noise and improve receiver performance. The RC circuit should be close to the receiver. The range with a 100 ohm resistor is at least 3 meters with the transmitter roughly pointing at the receiver, and a packet loss of less then 0.1 percent. To manage burst length limitations there is a short pause between characters, and only 7-bit characters are sent, with two stop bits. The 7-bit limit means that you can send all of the printing characters on the US keyboard, but no extended ASCII. All data is therefore sent as printable strings, NOT as raw hexidecimal.

Land’s writeup also includes a list of programs and packet format information.