evalKits.com Blog

Touch Sensors: No Code, Simpler Interfaces

2010-08-30T09:08:21Z

Many products need only basic on/off touch controls rather than sliders, wheels, and proximity sensors. Engineers might want to replace a mechanical switch with a touch control. Even in these cases, designing the controls themselves and their associated circuits can seem complicated. Cypress Semiconductor aims to change that perception and simplify sensor interfaces and designs. Now, engineers can easily add capacitive touch controls to many products where they hadn't thought to use them previously.

The new Cypress CapSense Express controller--CY8CMBR2044--relies on the company's auto-tuning technology that automatically adjusts for a sensor baseline and sensor threshold during power up and during use. So as environmental conditions change, the internal circuits detect them and adjust parameters so the switches continue to operate properly. The chip requires no code development and only a few external passive components, one of which controls whether an output acts like a toggle or only as a momentary pushbutton. Separate outputs reflect the state of each of four touch sensors. You don't need an I2C or SPI port to interface this chip to a microcontroller, for example. For a data sheet, visit: www.cypress.com/?docID=23419. For information about other CapSense products and design support, visit: www.cypress.com/?id=1575.

The chip incorporates a flanking-sensor suppression (FSS) capability that lets it properly sense activity on one sensor, ever with some overlap on nearby sensors. You can enable or disable this operation.

Equipment designers unfamiliar with capacitive-sensing controls might worry about the types of sensors they must fabricate, the substrate materials they plan to use, distances between sensors and the CY8CMBR2044, and so on. Cypress anticipated these concerns and provides a Design Toolbox spreadsheet that lets designers specify materials, overlay thickness, dielectric constants, approximate scan rate, and other parameters. Then the toolbox software provides recommended sensor-design information.

Engineers who want to dig deeper into sensor design can download MultiChart software that helps analyze internal information from CapSense ICs, obtained via a standard serial port. Pulling one of the CapSense pins to ground through a 5600-ohm resistor places that pin in a serial-port mode. The data sheet noted above and the application note, "Design Aids -- CapSense Data Viewing Tool, AN2397," explain how to obtain internal test information. Find this application note at: www.cypress.com/?docID=2425. In all likelihood, you won't need to do any debugging or testing, but the capability exists if you need it.

The CY8CMBR2044 chip can operate with a supply voltage of 1.71 to 5.5 volts and in a deep-sleep mode, it draws only 100 nA. The chip comes in a 3 x 3 mm 16-pad QFN package. --Jon Titus

Freescale Makes Consumer Wireless Controls Click

2010-08-25T03:08:38Z

The widespread use of handheld remote controls has caused consumer-electronic manufacturers to look beyond infrared signals to wireless control of TVs, digital set-top boxes, environmental controls, sprinkler systems, and even appliances. To answer the requirements for these short-range wireless controls, Freescale recently introduced the MC1323x system-on-chip family of microcontrollers for ZigBee RF4CE consumer electronics. You can use other communication protocols, too.

Each MCU in this family of three devices, includes an 8-bit HCS08 microcontroller, an IEEE 802.15.4 transceiver (2.4 GHz), flash memory, RAM and peripherals specifically tailored for engineers who design consumer products. The new system-on-a-chip devices provide for dual uses--infrared or wireless--so manufacturers can continue to offer IR-based controls that will provide compatibility with newer equipment. That approach "smooths" the transition from IR to wireless controls for equipment designers, manufacturers, and consumers. To start, Freescale expects to concentrate in three markets: consumer electronics, health-care products, and industrial controls, including HVAC equipment.

The three devices offer 82 Kbytes of flash and 5 Kbytes of RAM (MC13233C) or 128 KBytes of flash and 8 Kbytes of RAM (MC13234C and MC13238C). The latter IC also includes a USB interface.Freescale has samples of the MC13233C chip available now.

Engineers who want to investigate the wireless approach to remote control can buy several development kits, from basic USB "sticks" to complete development boards and software. For kit information, contents lists, software information, specifications, and prices, visit: www.freescale.com/webapp/sps/site/prod_summary.jsp?code=1323x_Dev_Kits. Kits start at $US 199

On the wireless side, the devices can use a simple MAC, IEEE-802.15.4, SynkrosRF, ZigBee RF4CE, or a standard ZigBee or ZigBee Pro stack. Use of a ZigBee protocol stack requires membership in ZigBee Alliance (www.zigbee.org) as an adopter member ($US 3500/year). For information about Freescale's SynkroRF protocol, visit: www.freescale.com/webapp/sps/site/overview.jsp?code=PROTOCOL_SYNKRO.

The ZigBee Alliance oversees the RF4CE protocol: www.zigbee.org/Markets/ZigBeeRF4CE/ApplicationsandAvailability.aspx.

If you have an application that could benefit from a small, low-power wireless controller, take a look at what Freescale has to offer. --Jon Titus

Wolfram Alpha: A Cool Site for Math, Facts, and Figures

2010-08-17T01:08:54Z

You might not have heard of Steven Wolfram, the genius behind Mathematica, a program that, "...seamlessly integrates numeric and symbolic computations, interactive document capabilities, an advanced programming language, and powerful connectivity." I've enjoyed watching demonstrations of Mathematica, but never could afford to plunk down $US 2500. The Home Edition at $US 295 tempts me.

Wolfram also created the Wolfram Alpha search engine: www.wolframalpha.com, which gives engineers, scientists, and students information and analysis that other Web sites lack. If you type in "US GDP 1950-2005" (without the quotes) you'll see how the Wolfram Alpha site interprets the input and then produces information in graphical form that include historical plots of gross domestic product in billions and trillions of dollars on a log scale. You also get real GDP and a GDP chain-weighted index. (For information on chain-weighted GDP, see: http://www.ssc.wisc.edu/~mchinn/chain_GDP.pdf.)

Want to see what a math function looks like? Just type it in and the Mathematica back end provides more information than you would find on other sites. The function sin(x)/x produces two plots, a series expansion, the derivative, the indefinite integral, and other information. Type "loan amortization" and you get a worksheet that lets you compute the present value of a given sum, number of compounding periods, and an interest rate.

Type "apple ibm intel" and you'll see stock values, stock-price histories, realized return vs. volatility, and return on a portfolio of these stocks. When I entered "utah unemployment 1990-2008" the Wolfram Alpha site displayed four helpful plots. The site isn't perfect, though. When I typed "boiling point vs. altitude," the results showed boiling points for several chemical elements. The phrase "water boiling point vs altitude" didn't do any better. Finally, "boiling point of water at 5000 feet" gave me the answer I sought.

The Wolfram Alpha site includes examples by topic, a gallery of examples, and a short video that explains how the site works and how to enter information to obtain useful information. Unlike, say, Google or Bing, Wolfram Alpha answers specific questions and does not dig up general information on a topic. So, sin(x)^4 + cos(x) provides good information, but "best brownie recipe" only tells you about the composition of a typical brownie (including 23 grams, 95 calories), not how to bake one.

You might want to buy a bag of brownies before you sit down to try Wolfram Alpha. It's addictive and you can spend a lot of time using it and just having fun with math equations and factual queries. I sure wish I had this type of tool in high school and college. --Jon Titus

LTC Chip Family Creates Pulses, Clocks, and Delays

2010-08-09T03:08:42Z

Linear Technology Corporation (LTC) has a family of interesting timing chips in SOT23 packages that let designers easily create five common timing functions:

voltage-controlled oscillator
low frequency oscillator
pulse width modulated oscillator
monostable pulse generator (one-shot)
delay

Each of the five ICs require from one to three external programming resistors and might require a few other resistors and a capacitor, depending on the chip and function needed. Find a datasheet for the LTC6990 Voltage Controlled Silicon Oscillator at: cds.linear.com/docs/Datasheet/6990f.pdf.

Linear Technology offers a series of 12 "Demonstration Circuit 1562A" boards that lets engineers test and evaluate the LTC699X-X family of TimerBlox circuits. The board's center area has mounting pads for a circuit that will accommodate any of the five ICs because the devices use a common pinout with the exception one pin. That pin acts as an output enable, trigger input, reset input, modulation input, or pulse input. You can find the board circuits and part numbers in the "Demo Circuit 1562A Quick Start Guide at: cds.linear.com/docs/Reference%20Design/DC1562aqs.pdf.

As of August 9, 2010, LTC does not sell the demo circuits on its Web site and distributors Digi-Key and Newark don't recognize the board part numbers.

The demo circuits include two oscillators, four pulse-width modulators, four one-shot circuits, and two delay circuits. The board leaves space with etched pads so engineers can breadboard other circuit components. Power and ground traces encircle the TimerBlox circuit.

You can find more information on the TimerBlox page on the LTC site: /www.linear.com/TimerBlox . LTC also offers er a complete set of TimerBlox LTspice models. The LTspice design tool is a high performance Spice III simulator, schematic capture and waveform viewer, available for download from Linear Technology. In addition, the TimerBlox can be quickly set up using the TimerBlox Designer, an Excel-based set-up tool that generates a schematic, with part name and resistor values, and a timing diagram based on the timing function parameters. --Jon Titus

Compensate for Voltage Drop in Power-Supply Connections

2010-08-03T02:08:16Z

The July 2010 issue of the Journal of Analog Innovation from Linear Technology included an article about how remote sensing can overcome voltage drops in power-supply connections. Engineers usually compensate for such drops--due to inherent wiring resistances--by using a sense connection at the point of load or using a point-of-load regulator. The former technique adds two extra connections and the latter adds an circuit for regulation at the load. Both take up PCB space and can add cost.

Linear Technology takes a different approach, called "virtual remote sense" (VRS) that measures the impedance of the power-supply connections and adjusts voltage output from the supply circuit accordingly. Circuits that apply this technique use a capacitor across the load and a Virtual Remote Sense chip (LT4180) at the power supply. The article includes many helpful schematic diagrams of power-supply circuits. You can download the complete article, "Virtual Remote Sensing Improves Load Regulation by Compensating for Wiring Drops Without Remote Sense Lines," at the Linear Technology Web site: http://cds.linear.com/docs/LT%20Magazine/LTJournal-V20N2-00-Cover-LT4180-Tom_Hack.pdf.

The LT4180 and its surrounding components also add cost, but you balance that against better voltage regulation. You can include the LT4180 in your power-supply circuit, where it provides feedback to the switching-regulator section.

Here's how Linear Technology's authors, Tom Hack and Robert Dobkin, explained the chip's operation...

The LT4180 VRS solves this [voltage-drop] problem by interrogating the line impedance and dynamically correcting for the voltage drops. It works by alternating the output current between 95-percent and 105-percent of the required output current. In other words, the LT4180 forces the supply to provide a DC current plus a current square wave with a peak-to-peak amplitude equal to 10% of the DC current. The decoupling capacitor at the load (which normally insures low impedance for load transients in non-VRS systems) takes on an additional role by filtering out voltage transients from the VRS square wave.

Because the capacitor is sized to produce an “AC short” at the square-wave frequency, the interrogating voltage square wave produced at the power supply is equal to V_SUPPLY(AC) = 0.1 × I_DC × R, measured in V_P-P. The voltage square wave measured at the power supply has a peak-to-peak amplitude equal to one tenth the DC wiring drop. This is not an estimate—it is a direct measurement of the voltage drop across the wiring over all load currents.

Minor signal processing creates a DC voltage from this AC signal, which is introduced into the power supply’s feedback loop to provide accurate load regulation.

The July issue of this journal also contains other articles that relate to power and analog circuits. It's worth taking a look. --Jon Titus

"Why Can't We Manage Large Projects?"

2010-07-29T10:07:17Z

Watts S. Humphrey of the Software Engineering Institute wrote an article with the same title for the July/August issue of Crosstalk, a journal sponsored by the US Department of Defense and other government groups. You can find the entire issue online at: www.stsc.hill.af.mil/crosstalk/2010/07/index.aspx.

Humphrey's article described causes for software-project failure or lateness and he notes:

"But the fact that these large projects keep failing suggests that program managers don’t know what to do. However, we must do something and it should by now be clear that relying on program managers to fix these projects isn’t working. This article suggests how to address these problems in a way that program managers can implement today."

The Software Engineering Institute at Carniege-Mellon University created the Team Software Process (TSP), and according to the article, "...one of its principal features was that its management system was based on precise, operational-level data. With the TSP, the developers gather and use data to manage their own work, and they use their data to accurately measure project status to within fractions of a day. TSP teams report their status to management every week, and management can see exactly where every element of every project stands. With precise status information, management can see small cost and schedule problems before they become serious. They can then take timely action to identify and resolve the problems."

Learn more about TSP at www.sei.cmu.edu/tsp/.

The 32-page issue of Crosstalk magazine concentrates on TSP and how companies and teams can adopt and adapt it to their specific circumstances. So far I've read only Humphrey's article and his interview with a magazine editor. But the magazine is in my stack for more attention over the next weekend.

Crosstalk has a small group of subscribers, but anyone involved with software can sign up for a print subscription or browse through back issues. The magazine publishes every other month. The Software Technology Support Center at Hill Air Force Base, Utah publishes the magazine. --Jon Titus

Radio to the Rescue

2010-06-29T12:06:31Z

On a recent morning, when I picked up the phone to check for messages, I heard nothing, not even a click. The phone company's connection had died. This incident served as a reminder about the fragility of communications we take for granted.

Our community has active volunteers who help prepare for emergencies and we run through a drill every six months. Emergencies rely on many types of communications, from "runners," or people on bicycles, up to two-way radio communications. We assume telephone and Internet communications will get knocked out quickly and that cell-phone systems will "die" after about four hours. Heavy use during an emergency will "jam" cell-phone communications.

So we use amateur-radio operators and their equipment for primary communications. Local hospitals here all have "radio rooms" with amateur-radio equipment, and even first responders have access to ham-radio communications via licensed operators.

People might think of radio as an obsolete way to communicate, and they often think of amateur-radio operators--or hams--as relics from a bygone day. Not so. Since the FCC dropped the requirement for Morse-code proficiency, the ranks of amateur-radio enthusiasts has grown considerable. Although some hams still communicate via Morse code, many others work with digital communications that have names such as packet radio, radio-teletype, PACTOR, PSK31, and others.

Because most amateur-radio equipment can operate from 12-V vehicle batteries, in an emergency they can operate almost continuously when main power dies. And, radio equipment travels well, either as handheld transceivers, portable or vehicle-mounted equipment, or equipment in a command-post trailer. After the 9/11 attack on the World Trade Center buildings, hams took their own equipment to New York City and established communication centers under the auspices of the Red Cross, Salvation Army, and other groups that otherwise had limited communication capabilities.

So, although we think of "wireless" communications as WiFi hot spots, cell phones, text messages and tweets, in an emergency, when all else fails, two-way radio communications usually can get through.

For information about radio communications in public service, visit the American Radio Relay League Web site at: www.arrl.org/public-service. The ARRL has more information on all aspects of amateur-radio communications and how to obtain a license. Many radio clubs conduct classes and run test sessions. --Jon Titus, KZ1G

TI MSP430 Computer Board Costs $4.30

2010-06-24T10:06:09Z

If you have put off taking a look at the MSP430 family of 16-bit MCUs from Texas Instruments, you can jump in for under five dollars. The new MSP430 MCU Value Line LaunchPad kit sells for $US 4.30 and the cost includes shipping (for a limited time). The small board provides an "emulation" section that communicates from software tools on a host PC with an MSP430 MCU chip in the MSP-EXP430G2 section of the board. The latter section provides a 20-pin DIP socket so you can plug in many types of MSP430 Value Line processors. The processors start at $US 0.25 each in large quantities.(You can program any MSP430 Value Line MCU on this board. And you can program any Spy Bi-Wire-enabled MSP430 device as well as any eZ430 target board. A 10-pin JTAG header provides the programming connection to external boards.)

The inexpensive kit includes two MCUs--an MSP430G2211 and an MSP430G2231--that you can plug into the 20-pin socket to program and debug your code. Each chip has 128 bytes of RAM and 2048 bytes of flash memory. The two MCUs both have 10 general-purpose I/O lines, a watch-dog timer and brown-out regulator. The 2211 also includes a comparator. The 2231 has an SPI or I2C communication port and an 8-channel 10-bit analog-to-digital converter.

So, you can't use these chips to control an ATM or large LED sign. But they'll handle alarms, game controls, sensors, small consumer devices, electronic locks, light control, and similar applications that don't require a lot of code.

The board breaks out all of the processor pins and it comes with male and female headers so you can decide which type to solder onto the board. For more information, including production-ready open source projects, visit www.ti.com/launchpadwiki-pr. You can download unrestricted versions of the TI Code Composer Studio (version 4) and the IAR Systems Embedded Workbench.

For more information, visit:

LaunchPad tool folder: www.ti.com/launchpad-pr

MSP430 MCU Value Line: www.ti.com/launchpad_value-pr

TI eStore: www.ti.com/launchpad-pr-es

Jon Titus

TI's ARM Cortex-A8 MPUs Enhance Sitara Family & BeagleBoard

2010-06-16T04:06:42Z

In late 2009, Texas Instruments introduced its Sitara family of ARM Cortex-A8 processors that use the ARMv7 processor-core architecture. In early June (2010) the company announced two new Sitara processors in the Cortex-A8 family, the AM3703 and the AM3715.

According to Texas Instruments, these MPUs are appropriate for portable data terminals, portable medical equipment, home and building automation, navigation systems, smart displays and human machine interfaces (HMIs) in industrial equipment. The AM3715 provides a 2-fold increase in graphics performance over previous Sitara devices, while the AM3703 would find use in non-graphic-intense designs. For more information, visit: tinyurl.com/2cpfzko.

TI provides a Linux kernel (2.6.32) board-support package, a Windows Embedded CE (6.0) board-support package, and a basic port for the Android operating system. Other software includes a full peripheral-driver library, example applications, development environment, and system utilities. According to TI's news announcement, these software packages give designers and developers an easy software migration path for product enhancements through the Sitara ARM MPUs and DaVinci video processors.

Engineers and product designers can order two types of evaluation modules, the AN37x and the AM/DM37x. Both cost $US 1495 each.

The AM37x module provides a 1 GHz AM3715 Cortex-A8 processor, 256Mbytes of RAM and 512Mbytes of flash memory, a WLAN/Bluetooth Daughter Card, 3.7-inch" LCD Touchscreen, keypad and many types of I/O ports.

The AM/DM37x module includes all the capabilities of the AM37x module and adds video-codecs and demonstrations and Windows Embedded CE.

If you want to start with a lower-cost board, consider the BeagleBoard-Xm, a small (3.25 by 3.25 inches) computer board that includes an ARM Cortex-A8 processor, although the information at beagleboard.org did not specify which Sitari-family microprocessor the board uses. The xM version of the BeagleBoard let developers run a full Linux operating system that can manage OpenOffice and the Firefox Web browser. Cost for the BeagleBoard-Xm: $US 179. For more information, visit: beagleboard.org/hardware-xM. The BeagleBoard "project" involves many engineers and programmers--and some hobbyists--who port software, create libraries, contribute add-ons, and provide other types of project support.

For information about the Cortex-A8 processor, visit: www.arm.com/products/processors/cortex-a/cortex-a8.php.

Are you a BeagleBoard user? How does it stack up against other low-cost boards? What do you like most or least about it? --Jon Titus

Please Just Give Me One More Gate!

2010-06-08T01:06:27Z

How many times have we created a circuit that needed just one more NAND gate or inverter? It didn't make sense to add another complete hex inverter or quad NAND-gate package, so we'd rework a design, maybe cram something into software, or give up and just add another IC. But sometimes it's easier and less expensive to add one logic element rather than rework an FPGA design or thousands of lines of code.

Last week I discovered the TinyLogic family of ICs from Fairchild Semiconductor that includes an inverter, NAND gates, OR gates, and configurable functions. Yes, that's one logic function per chip in either 5-pin SC70 or Fairchild's 6-contact MicroPak surface-mount packages. The latter measures about 1.5 by 1.0 mm. So if you need "just one more gate" you can drop in one of these small devices. Likely you can guess that the company aims these small devices at manufacturers of cell phones, MP-3 players and other small consumer-electronic devices. But anyone with a tight design and a low power budget can use them to their advantages.

The Fairchild TinyLogic family list includes other functions such as open-drain and three-state buffers, logic decoders, flip-flops, and latches, but I never found information about them. Perhaps they're already in the pipeline and will come along soon.

The TinyLogic ICs use an advanced CMOS technology that lets them operate with a supply-voltage range of 0.9 to 3.6V, yet they can drive up to 24mA, and have low propagation delays--on the order of a few nanoseconds. Fairchild has other logic functions in the TinyLogic family, too. For more information, visit: www.fairchildsemi.com/products/logic/tinylogic. You can download a TinyLogic product-line flyer at: www.fairchildsemi.com/collateral/logic/tinylogic_selection_guide_5-9-07.pdf.

Have you had to solve the I-just-need-one-more-gate problem? Share your experiences with us. --Jon Titus

Are You Confused About Windows Embedded?

2010-06-05T01:06:54Z

Most people involved with personal computers realize Microsoft has a new operating system (OS), called Windows 7 that replaces Windows Vista and Windows XP. System developers might not know Microsoft now has Windows-7-based operating systems for embedded products, thus the development of Windows Embedded Standard 7 (WES 7). The company says it will deliver, "...the power, familiarity and reliability of the Windows 7 operating system in a highly customizable and componentized form. OEMs can leverage Windows Embedded Standard 7 to create differentiated experiences and enhanced connectivity with Windows-based PCs, servers and online services on specialized devices, such as thin clients, digital signage and industrial controls for the enterprise, as well as set-top boxes (STBs), connected media devices (CMDs), and TVs for consumers." I believe "componentized" means developers can choose to add only the functions they need to save space and perhaps decrease boot-up times.

In applications that don't require a complete PC, Windows Embedded Standard 7 with Windows Media Center might offer an alternative to using either a commercial or a do-it-yourself operating system, or adding a complete Windows PC to a product. Microsoft also provided information about using WES 7 in digital signs. So if you create intelligent displays and signs that provide graphics and color, this OS might give you a head start.

More information on the capabilities and features of Windows Embedded Standard 7 as well as the entire Windows Embedded portfolio of platforms and technologies is available at www.microsoft.com/windowsembedded.

But things get a bit confusing because it's difficult to keep track of everything Microsoft does. A few days ago, the company also announced a community technology preview (CTP) for Windows Embedded Compact 7 (WEC 7). Microsoft makes the Windows Embedded Compact 7 CTP available now for developers at www.windowsembedded.com/compact7. The platform is expected to be released to manufacturing in the fourth quarter of this year. (Does anyone know--seriously--what a "platform is in this context?)

Unfortunately, the "Find out how you can get involved" link on the WEC 7 page goes nowhere as of now, June 4, 2010. But you can get to a page that helps you select a Windows OS based on an application, processor type, ROM space, and OS requirements. Visit: www.microsoft.com/windowsembedded/en-us/products/default.mspx.

I welcome comments about Windows 7, WEC 7, and WES 7. I'm no longer a Windows "user." --Jon Titus

What the Heck is a Grid-Dip Meter?

2010-05-24T03:05:24Z

The May 13, 2010 issue of EDN magazine included an article, "Punching Through the Ether with RF-Range Extenders," by technical editor Paul Rako. A photo in this story shows a Boonton Measurements Model-59 grid-dip meter. By coincidence the May 2010 issue of Elektor magazine included an article by Ronald Dekker, "Grid Dipper," that included a photo of a markedly similar instrument built in the 1950's. (See Note below.)

Back in the early '80's, I bought a Kenwood DM-81 Dip Meter and have used it extensively to determine values of inductors, help tune transmission lines, and determine the response of tuned circuits. At its simplest, a grid-dip meter comprises a variable-frequency RF oscillator with a variable capacitor and a set of plug-in coils. The DM-81 covers the from 700 kHz up to about 250 MHz with seven plug-in coils. When I place the oscillator coil close to a tuned circuit, the meter indicates a decrease, or dip, in current when its frequency equals the frequency of the tuned circuit.

The Elektor article describes a tube-based (valve-based) oscillator circuit and explains how the tube-oscillator circuit's grid current decreases as a nearby circuit absorbs energy at its resonant frequency. The Kenwood manual lists resonant-frequency measurements, use of a capacitive probe, antenna measurements, signal generation, crystal tester, absorption frequency meter, field-strength indicator and market generator.

As far as I know, Kenwood no longer manufactures the DM-81 grid-dip meter, but you can find a scanned copy of the short manual, schematic diagram, and parts list at: www.ae7q.net/doc/public/dm81/Dm81.html. For a clearer schematic diagram, visit: http://www.hendrielane.com/05-24-10-DM-81.jpg.

Image courtesy of KE6JDH and qrz.com.

Alfa Electronics sells a DM-4061A Grid Dip Meter ($US 90) that looks a lot like the Kenwood model. And MFJ Enterprises sells the MFJ-201 Dip Meter ($US 150). You might find a bargain on Ebay, but ensure you get a manual and a complete set of coils. I'd hold out for a DM-81, though, because it had internal coil storage so the coils won't tend to "wander away" on your lab bench. And it uses a 9V battery.

Do you have a grid-dip meter? Have you ever used one? --Jon Titus

Note: For a copy of the Elektor article, go to: www.elektor.com/magazines/2010/may/grid-dipper.1322032.lynkx. Elektor will sell you the entire May 2010 magazine for $US 7.50, or you can use Elektor credits to pay for the single article. I have no idea what Elektor credits involve.

For the EDN article, go to: www.edn.com and look under the top-right tab "Magazine" to find issue archives.

Let GOPHER Find the Best MCUs

2010-05-19T12:05:08Z

You and your colleagues face a difficult problem when you must choose the best microcontroller (MCU) for a design. Because manufacturers offer many types of MCUs with a wide spectrum of capabilities, it proves difficult to determine which one to use. Rick Hully at GruntWare (www.gruntwareinc.com) has created a database of MCU specifications that greatly simplifies the "hunt" for an MCU. The Gopher software provides a database of normalized information that includes information about conflicting pin assignments. So, if you need an MCU with two UARTs, 18 digital I/O lines and an I2C port Gopher will narrow your list to only those devices that provide this capability--without pin-assignment conflicts. So you no longer need to go through MCU specs to ensure the UARTs don't gobble up the same pins you want to use for digital I/O lines.

For more information about Gopher, you can read my hands-on review published in Design News magazine. Hully has a copy posted on the GruntWare site at: www.GruntWareInc.com/2009-06-01 Design News Article.pdf.

Hully recently contacted me about new enhancements to Gopher. One, called the "Application Search Configurator," lets developers and engineers describe in a sentence an application, such as a motor controller. Afterward, Gopher constructs the proper search equation and identifies the MCUs that meet the stated requirements. Now you can type in, for example, "Motor control of a brushless 3-phase DC motor using BEMF for control with optimal MCU op amps for use with the BEMF." Wow, what a great way to start a search! (BEMF denotes back-emf; a common motor-control technique.)

The Gopher Pro version also lets you enter an MCU part number and look at parameters and specifications. Then you can find competitive MCUs.

GruntWare has done a nice job with Gopher and the database now covers 15,455 MCUs from 25 vendors. I have used this software and recommend it highly as a way to find the MCU you need without going through mounds of vendor specs to narrow your selection. --Jon Titus

Two Cool Embedded Tools

2010-05-10T04:05:21Z

While at the Embedded Systems Conference in San Jose, California in late April (2010) I uncovered a couple of handy, interesting, and useful devices.

First, Saelig, a company that sells a variety of interesting products, now has an SD-to-USB adapter (Mobidapter, $US 39.95). Many engineers and programmers carry information, images, code, and documents on a USB memory stick, but if a smart phone, PDA, or embedded device lacks a USB port (or has all USB ports in use), the adapter lets them plug a USB stick into the adapter and the adapter into an secure-digital card (SD) slot. And, you can use a USB stick as a backup rather than an SD card. The adapter body has a Micro-SD connector, but add-on adapters let you use it in mini-SD and full-size SD sockets, too. For more details, go to: www.saelig.com/product/MIO001.htm.

Second, Micro Computer Control (MCC) has an i2cStick that gives you a connection between a USB port and an I2C bus. The I2C bus lines operate at 23, 86, 100, or 400 kbits/second and at bus voltages of 3.3 or 5 volts. You get free I2C EEPROM programming software, I2C message center software, a .NET library, and Visual Basic, C, C++, and MFC sample projects. The company offers an optional LabVIEW library, too.

When you must connect to an I2C bus to troubleshoot, control, program, or monitor I2C devices, the pocket-size i2cStick should do the job. Prices range from $US 150 to $US 250 depending on the interface cable you require and the quantity purchased. For more information, visit: www.mcc-us.com. And while you're on the MCC site, take a look at the IP-101 I2C Prototyping Board that offers designers and students a way to experiment with and test I2C-bus devices and circuits. --Jon Titus

AVR MCUs Add Floating-Point Math

2010-05-03T01:05:56Z

Years ago minicomputer manufacturers supplied a software "floating-point package" that let programmers work with floating-point numbers. The PDP-8 family of minicomputers, circa 1970, used 12-bit words and a floating-point value required three of them; one for an exponent and sign, and two for the mantissa and its sign. Special op codes identified basic math operations and a square and square-root function. If you wanted anything else, you were on your own.

Today's programmers and engineers have it easy by comparison because many microprocessor and microcontroller families include floating-point math operations as a matter of course.

Atmel, for example, recently announced several new microcontrollers in the 32-bit UC3 family will include a floating-point unit (FPU) that can handle single-precision values. The addition of an FPU might let you eliminate a signal-processing chip from a design or greatly simplify software that previously used fixed-point or integer values. The AVR32 Studio already can handle floating-point values, so there's no need to buy new development tools or upgrade them. According to an engineer at Atmel, "The only difference in the AVR UC3 Toolchain is that now the CPU can perform operations on floating point numbers in a single cycle. In the past, this involved library functions that required hundreds of instructions."

Single-precision floating-point math means you can operate with values between 1 x 10^-38 and 1 x 10⁺³⁸. And Atmel's FPU complies with the IEEE 754 standard. So, a single-precision value use one bit for the sign (+ or -) of the value, eight bits for an exponent (-126 to +127), and 23 bits for the numerical value. Compliance with the IEEE standard ensures the proper representation of values, independent of CPU or FPU architecture, proper rounding of values, and the correct handling of exceptions, such as an attempt to divide a value by zero. It also lets programmers take advantage of many code libraries and proven algorithms such as those created in MatLab.

But floating-point information can create a debugging problem: How do you examine FP values when debugging? I don't know of any MCU development tools that can "watch" or "trace" floating point information and present it in a form we humans can read. I'd rather see 4.389 x 10⁵ than a long string of binary or hexadecimal values. If you know of development tools that can display FP values in scientific or engineering format, please let us all know. --Jon Titus

Addendum: FPU Benchmarks

The Embedded Microprocessor Benchmark Consortium (EEMBC) plans to create benchmarks that will track the performance of embedded processors with floating-point unit (FPU) hardware. The new benchmarks will let people evaluate FPU performance based on consistent and controlled data.

Examples of the real-world applications that the forthcoming FP suite will likely address include DSP filtering, audio encoding, video encoding, and motor control. According to the EEMBC, the suite might also include a series of generic kernels such as bi-cubic filtering and fast Fourier transforms (FFTs), which are particularly revealing of FPU performance. Likewise, the benchmarks will measure the performance difference between single-precision (32-bit) and double-precision (64-bit) floating-point operations.

The EEMBC floating-point working group seeks contributions of benchmark kernels from engineers and programmers in industries that use embedded systems. For more information, please contact Markus Levy, EEMBC president (www.eembc.org).

References:

For an overview of floating-point numbers, visit: en.wikipedia.org/wiki/IEEE_754-2008.

I also recommend Michael L. Overton's book, "Numerical Computing with IEEE Floating Point Arithmetic," Society for Industrial and Applied Mathematics, Philadelphia, PA. 2001.