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Circuit Cellar's editorial team comprises professional engineers, technical editors, and digital media specialists. You can reach the Editorial Department at editorial@circuitcellar.com, @circuitcellar, and facebook.com/circuitcellar

Translating Values: Number-to-ASCII Conversion (EE Tip #147)

There is a neat trick for performing the number-to-ASCII conversion. (We are not sure of this trick’s origin. We’d love to hear from anyone who saw it long ago and can us more about it.)ASCII-iStock_000007340231_Large

One starts by defining an array in the 8051 family microcontroller’s code segment using the following command:

HEX_NUM: DB ‘0123456789ABCDEF’

Following the conventions that now seem to be pretty standard for 8051 family assemblers, this command cause an array whose values are the ASCII values of the characters within the single quotes to be stored in the code segment (assuming that that is the segment in which you are working). To convert a number between 0 and 15 to the relevant ASCII value, you now need only store the value to be converted in the accumulator, A, and the location of the array HEX_NUM in the data pointer, DPTR. You then give the single command MOVC A, @A+DPTR. This command uses the current value of the accumulator, the value you are looking to translate into an ASCII value, as an offset and reads the relevant value of the array into A (thus overwriting the value you wanted to “translate” with the correct translation). Thus, if A starts off with a 5, it ends up with the sixth element of the array (as there is an element with a zero offset)—which is just the ASCII value of 5, and all of this takes place without any hard work on the part of the programmer.—Ahron Emanuel, Shlomo Engelberg, and Dvir Ophir (“Virtual Instrumentation, Circuit Cellar 294, 2015)

Microcontroller-Based Duodecimal Clock Project

Programmers and embedded circuit designers know that decimal is not the preferred number system for digital devices. Binary, octal, and hexadecimal numbers rule the day, so they’re comfortable using strange number systems. Clocks are essentially duodecimal, or base-12, devices. Devlin Gualtieri designed a two-digit clock that only an engineer would love (and know how to read).

The seven-segment LED displays were mounted on the foil side of a single-sided circuit board. I used single-row, in-line sockets to facilitate soldering. The sockets also elevated the displays above the circuit board and the SMT resistors placed beneath the displays.

The seven-segment LED displays were mounted on the foil side of a single-sided circuit board. I used single-row, in-line sockets to facilitate soldering. The sockets also elevated the displays above the circuit board and the SMT resistors placed beneath the displays.

In Circuit Cellar 294, Gualtieri writes:

Digital timekeeping has supplanted mechanical timekeeping not simply because it’s usually more accurate, but because it’s inexpensive. Digital alarm clocks are available everywhere for about $10. You can build the clock in this article for a few dollars more, but with a larger share of satisfaction.

Many years ago, I started designing with Microchip Technology PIC microcontrollers. Since I now have the necessary tools for PIC development, it would be hard for me to change. Fortunately, there’s no reason for change, since PIC microcontrollers are adequate for most embedded designs, and they’re quite inexpensive. This design uses the PIC16F630 microcontroller.

PIC microcontrollers have a built-in oscillator with about a percent accuracy, which is reasonable for many embedded applications. This accuracy comes from digitally trimming an internal resistor-capacitor oscillator on the chip. One percent accuracy is not adequate for a clock, since that would be a quarter of an hour’s error each day.

It is possible to use an inexpensive 32.768-kHz tuning fork crystal with a PIC. This frequency is useful for clocks, since a power of two will divide this frequency to 1 Hz. However, this slow clock rate prevents rapid computation and some useful functionality, so I didn’t use such a crystal in this circuit. Instead, I used a half-sized 10.000-MHz TTL canned oscillator. Canned oscillators are easy to use, highly accurate, and not too expensive.

Seven-segment LED displays are common circuit items, and this clock has a two-digit LED display. One digit is for hours, and the other digit is for the twelfth fraction of the hour. It’s straightforward to display the numbers, zero through nine, on a seven-segment display, but 10, 11, and 12 pose a slight problem. The problem of the twelfth hour disappears when we use zero for that digit. This convention is familiar to most technical people.

In the hexadecimal convention, 10 is represented by an “A,” and 11 is represented by a “B.” A capital letter “A” is easy to show on a seven-segment display, but a capital letter “B” looks just like an eight. As a compromise, we could use a lowercase “b,” instead.

We could also use a capital “E,” for 11, but having an “E” follow an “A” disturbs my hexadecimal sensibility. Although I’m not dyslexic, when I see a “b” on a seven-segment display, I think “six.” Another common notation, which I learned in my elementary school “new math” courses, is to use “t” for 10 and “e” for 11. Figure 1 shows possible number representations for ten and eleven, including the ones I chose for this clock.

Representing 10 and 1 on a seven-segment display. The “t” representations are somewhat abstract, but they can’t be confused with other characters. The last pictured in each category are my choices, since they’re easiest to read.

Representing 10 and 1 on a seven-segment display. The “t” representations are somewhat abstract, but they can’t be confused with other characters. The last pictured in each category are my choices, since they’re easiest to read.

Gualtieri goes on to describe the circuitry.

One way to minimize I/O pin count in a microcontroller circuit is to use multiplexing whenever possible. If we were to drive each seven-segment display and their decimal points individually, we would need 16 output pins. If we multiplex, we need just nine; that is, eight for the segments and decimal point, and one extra for the digit select.
The segments on the displays need a reasonably high current, and they also need about 4.5 V drive. That’s because they’re 1″ displays with two LEDs connected in series for each segment. For this reason, the display chips are driven from a 12-V supply, and the microcontroller interfaces with two 7406 TTL open-collector inverter/driver chips. Green displays were used, but other colors are available.

Digit select is easily accomplished with two transistors, also driven by sections of a 7406. The 5-V power for the PIC microcontroller and the clock oscillator is derived from a voltage regulator powered by the 12-V supply. A 12-V “wall wart” is a safe and convenient way to power this circuit, which is shown in Figure 2. The maximum current draw for my circuit was 250 mA. The circuit has two buttons for setting the clock by ramping the digits up or down.

This is the duodecimal clock’s circuitry. One nice thing about most embedded systems projects is that the software allows reduction in hardware complexity.  The particular displays used were green Lumex LDS-AA12RI displays.

This is the duodecimal clock’s circuitry. One nice thing about most embedded systems projects is that the software allows reduction in hardware complexity. The particular displays used were green Lumex LDS-AA12RI displays.

The nearby photo shows the the clock mounted in a custom case. You can see an AM/PM dot and the seconds flashing dot. The time setting buttons are mounted at the rear of the enclosure, but you could place them anywhere. A green filter increases the digit contrast.

The clock mounted in a custom case

The clock mounted in a custom case

The complete article appears in Circuit Cellar 294 (January 2015).

New Ultra-Low Power Precision Op-Amps

ON Semiconductor recently unveiled a new family of ultra-low power precision operational amplifiers. The precision NCS325 and NCS333 CMOS op-amps deliver zero drift operation and quiescent current for front-end amplifier circuits and power management designs.NCS325-333-Hires

The op-amp devices enhance the accuracy of motor control feedback and power supply control loops, thereby contributing to higher overall system efficiency. These devices are complemented by the new NCV333 automotive-qualified (AEC-Q100 grade 1) op-amp offering similar functional performance for power train, braking, electronic power steering, valve controls, and fuel pump and fuel injection system applications.

Features include:

  • High DC precision parameters, such as the 10 µV maximum input offset voltage at ambient temperature and the 30 nV/°C of offset temperature drift
  • Minimal voltage variations over temperature along with close to zero offset
  • Rail-to-rail input and output performance and are optimized for low voltage operation of 1.8 volt (V) to 5.5 V, with a best in class quiescent currents of 21 µA and 17 µA respectively at 3.3 V.
  • Operate with a gain bandwidth of 350 kHz with ultra-low peak-to-peak noise down to 1.1 µV from 0.1 Hz to 10 Hz.

The NCS325 is available in a 3 mm × 1.5 mm five-pin TSOP package. It costs $0.35 per unit in 3,000-unit quantities.

The NCS333 comes in a 1.5 mm × 3 mm SOT23-5 package or in a 2 mm × 1.25 mm SC70-5. It costs $0.5 per unit in 3,000-unit quantities.

Microchip Joins Linux Foundation & Automotive Grade Linux

Microchip Technology recently announced that it joined The Linux Foundation and Automotive Grade Linux (AGL), which is an open-source project developing a common, Linux-based software stack for the connected car. Additionally, Microchip has begun enabling designers to use the Linux operating system with its portfolio of MOST network interface controllers.Microchip MOST

AGL was built on top of a stable Linux stack that is already being used in embedded and mobile devices. The combination of MOST technology and Linux provides a solution for the increasing complexity of in-vehicle-infotainment (IVI) and advanced-driver-assistance systems (ADAS).

The MOST network technology is a time-division-multiplexing (TDM) network that transports different data types on separate channels at low latency and high quality-of-service. Microchip’s MOST network interface controllers offer separate hardware interfaces for different data types. In addition to the straight streaming of audio or video data via dedicated hardware interfaces, Microchip’s new Linux driver enables easy and harmonized access to all data types. Besides IP-based communication over the standard Linux Networking Stack, all MOST network data types are accessible via the regular device nodes of the Linux Virtual File System (VFS). Additionally, high-quality and multi-channel synchronous audio data can be seamlessly delivered by the Advanced Linux Sound System Architecture (ALSA) subsystem.

Support is currently available for beta customers. The full version is expected for broad release in October.

Source: Microchip Technology

CY8CKIT-042-BLE Bluetooth Low Energy Pioneer Kit

At just $49, Cypress Semiconductor’s CY8CKIT-042-BLE Bluetooth Low Energy Pioneer Kit is an affordable tool for creating BLE applications with a PSoC 4 and PRoC BLE devices. The kit supports system-level designs using the PSoC Creator IDE. It is compatible with Arduino shields hardware.IMG_20150106_080852956_HDR

The kit comprises:

  • BLE Pioneer Baseboard preloaded with CY8CKIT-142 PSoC 4 BLE module
  • CY5671 PRoC BLE Module
  • CY5670 – CySmart USB Dongle (BLE Dongle)
  • A quick start guide
  • USB Standard A-to-Mini-B cable
  • Four jumper wires (4 inches) and two proximity sensor wires (5 inches)
  • A coin cell (3-V CR2032)

Source:  Cypress Semiconductor

GP691 ZigBee Radio Chip and GPM6000 Modules for IoT

At CES 2015, GreenPeak Technologies announced a new GP691 ZigBee communication controller chip and GPM6000 integrated ZigBee modules for Internet of Things applications and smart home devices.IoTGreenPeak

The GP691 ZigBee communications controller provides IEEE Standard 802.15.4-compliant robust spread spectrum data communication in the worldwide 2.4-GHz band. It can run the full stack and application for ZigBee applications, including ZHA and ZLL profiles. In addition to a radio transceiver, the GP691 comprises a real-time Medium Access Control (MAC) processor, microcontroller, security engine, 16-KB RAM, and 248-KB flash memory. The GP691 is over the air upgradable and includes support for new 802.15.4-based standards upon availability, such as Thread.

ZigBee 3.0 supports a wide range of applications (e.g., home, industrial automation, and smart energy). IEEE 802.15.4-compliant, it can cover a complete home with multiple floors. Plus, it can manage dead spots and Wi-Fi interference via mesh networking. ZigBee 3.0 also supports large networks comprising thousands of devices, which also makes it suitable for industrial applications and building automation. ZigBee 3.0 also includes Green Power, part of the ZHA and ZLL profiles, which supports energy harvesting and battery-free applications. Without requiring batteries, these self-supporting devices typically generate (harvest) just enough power to transmit a brief command to the network via ZigBee.

With its partner Universal Scientific Industrial (Shanghai) Co, Ltd (USI), GreenPeak developed “an integrated module for the GP691 that reduces product design company’s time to market without having to solve RF product integration challenges or to worry about international wireless certification.”

The 25 x 17 x 2.5 mm pre-integrated, pre-certified module adds a power stage/LNA providing up to 20-dBm output power, special transmit and receive circuitry, and an integrated antenna plus a connector for a second external antenna enabling antenna diversity configurations, which all together, allow for greater range and robustness, providing coverage throughout an entire home. This module will be offered as the first in the GPM6000 module series optimized for smart home solutions.

Source: GreenPeak

Tips for Measuring Small Currents

Most inexpensive hand-held multimeters have measurement ranges from several amps to single-digit milliamps. While generally handy, such meters are insufficient for sensitive current measurements. There is a solution though. With the following project, you can extend the current measurement range from milliamps down into the nanoamp and picoamp range with simple, low-cost circuits.

In his January 2015 article (Circuit Cellar 294), David Ludington writes:

Most inexpensive hand-held multimeters have current measurement capability. The measurement range for these meters extends from several amps down to single-digit milliamps and sometimes into the microamp range. While this measurement capability is sufficient for many applications, there are times when more sensitive current measurement is required. There are meters available which measure much lower levels of current, but these meters are also more expensive and are often dedicated to just this one measurement function.

The goal of this article is to extend the basic hand-held current measurement range from milliamps down into the nanoamp and picoamp range with relatively simple, low-cost circuits. First, I’ll describe several types of current sources with their relevant performance characteristics that affect measurement circuits. Then, I’ll present practical circuits that deliver high performance at low cost. Each of these circuits will be analyzed to determine what level of measurement performance can be expected. General design issues common to all of the circuit techniques will also be discussed and recommended circuit component and layout techniques will be provided. Finally, two of the circuits will be discussed that were built and tested to demonstrate the desired goal of measuring nanoamp and picoamp currents.

CURRENT SOURCES

Figure 1 shows several types of current sources. Figure 1a is the symbol of what electrical engineers call an ideal current source. It can have any level of current at the output and the output impedance is infinite. The result is that the output current is not affected at all by the characteristics of the measurement circuit. Of course no actual current source is ideal, but this is still a useful concept for approximating actual circuits and is used as a source in circuit simulation programs such as PSPICE.

Figure 1: The current sources: ideal (a), semiconductor (b), and resistive (c)

Figure 1: The current sources: ideal (a), semiconductor (b), and resistive (c)

Figure 1b shows a current source which uses semiconductor transistors (either bipolar or FET). In this circuit, the output impedance is not infinite but can still be quite high (megohms). This means that varying voltages at the collector of the bipolar transistor or drain of the FET transistor have little effect on the output current as long as the voltage is not large enough to affect transistor operation.

Figure 1c is the least ideal of the current sources. The current is generated by the voltage difference across the resistor R2. Any measurement voltage developed by the measurement circuit directly affects the voltage difference across the source resistor. This changes the current that is measured which can result in measurement error. Having said that, Keithley Instruments in Low Level Measurements Handbook (6th edition, page 2-20) uses this current source model in defining what they call the feedback ammeter (also transimpedance amplifier). It may well be that, in real-world circuits, this model is the one that describes the majority of practical applications.

Although the current sources just described are not part of the measurement circuit itself, it is helpful to understand their limitations so that the measurement circuits can be designed to disturb the current source as little as possible. In this way, measurement error is minimized.

CURRENT MEASUREMENT CIRCUITS

In the past, current was measured directly with a moving coil meter. Now using semiconductor technology, voltage is the parameter that is measured directly. The current to be measured is first converted to a voltage by flowing through a load resistor. The resultant voltage is then measured and along with the load resistor is used to calculate the input current.

Figure 2: Current measurement circuits: resistive (a), transimpedance (b), and integrator (c)

Figure 2: Current measurement circuits: resistive (a), transimpedance (b), and integrator (c)

Figure 2 and Figure 3 show several circuit techniques which are used to convert current to a voltage. Figure 2 shows the basic techniques, while Figure 3 shows modifications to two of these basic circuits, which give more accurate results and extend the measurement range. The symbol for the input current used in these circuits is the same as the symbol for the ideal current source used in Figure 1; but in this case, it is used to show where the input current connects to the measurement circuit and can represent any of the described current sources.

Figure 3: Modified current measurement circuits: modified resistive (a) and modified transimpedance amplifier (b)

Figure 3: Modified current measurement circuits: modified resistive (a) and modified transimpedance amplifier (b)

RESISTIVE CIRCUIT

Figure 2a is the least complicated of the measurement circuits. In this circuit, the current source is connected to one end of the load resistor R1 and the other end of the resistor is connected to ground or some other reference point. The voltage developed across this resistor is measured with the voltmeter and used to calculate the input current. This circuit is very simple and is often used on the spot with an available resistor for quick measurements at the workbench or in the field.
The voltage that is developed across the load resistor is called the burden voltage. For a current source that is nearly ideal (such as the transistor source), the burden voltage has relatively little effect on the current being measured unless it is large enough to change the internal working of the current source. For resistive current sources, the burden voltage can directly interact with the current source and give erroneous current readings. This occurs because the load resistor becomes part of the current generating resistance which reduces the current. To minimize this interaction, the load resistor should be much smaller that the output resistance of the current source. The corresponding burden voltage will then also be small.
When a simple hand-held voltmeter is used, the measured voltage cannot be too small because these meters rarely measure below 1 mV. Thus, a compromise is needed between measurement accuracy and a low voltage burden.

Most hand-held meters have a 10-MΩ input impedance on the voltage scale. The load resistor R1 will be in parallel with the meter impedance and needs to be selected appropriately to give the desired equivalent measurement resistance. An example in Table 1 shows the resistor values needed to give a measurement voltage of 50 mV for the given currents. This fairly low value of measurement voltage significantly decreases the burden voltage while at the same time providing enough voltage to give measurement accuracy on the order of 10%.

Table 1: Resistor Values versus Input Current for Resistive Circuit (*Rounded off value. Less than 0.1% error.)

Table 1: Resistor Values versus Input Current for Resistive Circuit (*Rounded off value. Less than 0.1% error.)

When making a current measurement with the resistive circuit, it is always a good idea to try several resistors of different values to see what voltage results. If changing resistor values by a certain amount changes the measurement voltage by the same amount, then the source current is not being affected by the measurement (burden) voltage. In this case you can use the higher value of resistance to get more output voltage and more measurement accuracy. Conversely, if the corresponding measurement voltage increases less than the amount of the resistor value change, the source current is being affected by the measurement circuit and the smaller resistor value should be used.
A small modification to the circuit as shown in Figure 3a gives improved performance by removing the burden voltage at the expense of adding a variable power supply. This can be particularly useful as a quick measurement tool using an available workbench power supply. The power supply is adjusted until VOUT is 0 V. The value of the current is then obtained by dividing the measured value of the power supply voltage by the resistance R1. In this way the burden voltage is removed and the load resistor can be increased so that the power supply voltage can be greater than 50 mV. This will give more accuracy in the measurements.
Because VOUT is zero, the leakage current going into the hand-held voltmeter is zero and the finite input impedance (10 MΩ) of the meter does not affect the measurement. Even when VOUT is not exactly zero, the leakage current is still small. For example, for VOUT < 5 mV, the leakage current will be less than 500 pA. This gives measurement accuracy of 1% or better for input currents greater than 50 nA. Since the resistor R1 in this modified circuit is not developing a burden voltage, the resistor value is decoupled from the input current and can be any practical value depending only on the maximum voltage of the power supply.

TRANSIMPEDANCE AMPLIFIER

Figure 2b shows the circuit for a transimpedance amplifier. This is perhaps the most versatile of the current measurement circuits in that it can cover a large current measurement range using a simple circuit. In this circuit, the output from the current source is connected to the negative input of the operational amplifier while the positive input of the amplifier is connected to a reference voltage. This reference voltage is typically the circuit ground when there are bipolar power supplies and some intermediate voltage when there is a single power supply.
The inputs of an operational amplifier have very high input impedances (greater than 1 GΩ) so that little current goes into the amplifier. Thus, the input current drives the negative input toward one of the power supply voltages depending on the polarity of the input current. This causes a voltage difference between the amplifier inputs which is then amplified with the large internal open loop gain of the amplifier. As a result, the amplifier output voltage moves in a direction to provide current through resistor R2 which is opposite to the input current. Equilibrium is achieved when the amplifier output voltage is such that the current through R2 is equal in magnitude to the input current. With an ideal amplifier and no offset voltage, this results in 0 V at the negative terminal matching the voltage at the positive terminal. Only the value of resistance R2 and the amplifier output voltage are needed to determine the input current. Since we know the resistance value and can measure the output voltage, we can calculate the current through R2 which will equal the magnitude of the input current.
Since there is no burden voltage, the input current is not affected by the value of the feedback resistor R2 or the magnitude of the output voltage. The output voltage is constrained by the power supply voltages, but in principle there is no constraint on the value of the feedback resistor. Table 2 shows R2 resistor values for several nominal input currents for an output voltage (VOUT) of 1 V.
As seen in Table 2, the resistor values get quite large for small currents. These large value resistors are expensive and are often also physically large. Also, circuit constraints like stray capacitance can have an appreciable effect on the circuit when the resistor value is large.

Table 2: Resistor values for nominal input currents and VOUT = 1 V

Table 2: Resistor values for nominal input currents and VOUT = 1 V

There are two ways to reduce the resistor value required for a particular input current. One way is to allow smaller voltages than 1 V to represent the input current. This is acceptable as long as all anomalous voltages in the circuit due to circuit imperfections are calibrated out. This calibration can be either physical using potentiometers to cancel offset voltages. Alternatively, data calibration can be used by measuring the output voltage without the input current and then subtracting that data from the output voltage with the input current. Thus, as the input current (and corresponding output voltage) are reduced, the measurement voltage will still have sufficient accuracy.
The second way to measure lower values of current with a lower resistor value is to use the modified transimpedance amplifier shown in Figure 3b. Here, the output voltage is reduced by the voltage divider consisting of R3 and R4 before driving the feedback resistor R2. If the feedback resistor here is the same as the feedback resistor without the divider, the current flowing to the negative input terminal will be less than before. The internal gain in the amplifier will make the output voltage larger to compensate. For a voltage division of 10, the input current is 10 times lower for the same output voltage as before. One caution: although this circuit does give flexibility in the design, care is needed because there is an amplifier voltage gain equal to the divider ratio. The internal offset voltage and noise voltage of the amplifier are multiplied by this amplifier gain along with the current signal.

The complete article appears in Circuit Cellar 294 (January 2015).

 

Seven Engineers on the Future of Electrical Engineering

The Circuit Cellar staff thought it would be interesting to kick off 2015 by asking several long-time contributors about the future of electrical engineering and embedded systems. Here we present the responses we received to the following questions: What are your thoughts on the future of electrical engineering? What excites you? Is there something in your particular field of interest that you think will be a “game changer”?

STEVE CIARCIA: Frankly speaking, if I was smart enough to accurately predict the future, I wouldn’t be doing all this again. Seriously, “What excites me in the future?” shouldn’t be the question I’m answering here. Instead, it should be  how much does all this embedded stuff we’re seeing and talking about today look like a classic case of déją vu to me. Circuit Cellar started 40 years ago in BYTE to promote my enthusiasm for professional-level DIY computer applications (albeit mostly embedded). The names have changed to Maker this and that and Raspberry Pi whatever, but what once was, still is. Solder fumes aside, Circuit Cellar has always been about nurturing the talented engineer who designs the game changer. (Steve is an electrical engineer who founded Circuit Cellar in 1988.)

DAVID TWEED: Embedded technology is becoming more pervasive, appearing in more and more places in our lives. Embedded processors have become as powerful as desktop machines were just a few short years ago, and the their ability to connect to the world at large through high-bandwidth wireless communications has grown to match this. This is both exciting and scary, because it becomes a powerful enabler for both positive and negative changes in how we live our lives. Take the ubiquitous “smart phone” as an example. It can process two-way audio, video, GPS data, and an Internet connection simultaneously in real time. This enables powerful applications such as GPS-based route finding that can give you verbal and pictorial directions to get you where you want to go. But, as anyone who watches the popular crime drama N.C.I.S. knows, that same technology can be used to track your phone’s location, along with everything it can “see” and “hear,” including the phone calls you have made. While that kind of surveillance can be used it positive ways, such as to aid you in an emergency, it can also be used to invade your privacy. Can you really be sure that everyone in law enforcement and other areas of government has only your best interests in mind when accessing your data? The increased power of embedded systems means that autonomous mechanisms gain capabilities they didn’t have before. Fully-autonomous vehicles—cars, trucks, trains, and aircraft—will be able to carry people and goods long distances over arbitrary routes. Factory automation will become more generic, because complex general-purpose mechanisms will be as easy to use as purpose-built mechanisms that only do one thing, because the software will manage all of the low-level details of “training” the system. Machine vision will be an important part of this, giving the system the feedback it needs to interact with objects and people. “With great power comes great responsibility.” This has never been more true. I’m excited by the possibilities that increasingly powerful embedded technology will open up for us, but let’s make sure that it is used responsibly! (David is a professional electrical engineer and long-time Circuit Cellar author and technical editor.)

ROBERT LACOSTE: I think the most significant change in embedded systems these last years is the nearly mandatory inclusion of Internet connectivity. It’s called the Internet of Things (IoT). Just enter those three words in Google and the 752 million results you get will show it’s a quite hot topic. When a customer meets with us to discuss a potential new product (whatever it is), the question is no longer: “Should it be connected?” The question is: “How should it be connected?” Having said that, the key difficulty is the long list of wireless protocols trying to become the ubiquitous solution for IoT: Wi-Fi, Bluetooth, Bluetooth Low Energy, ZigBee, Zwave, 6LowPan, and a hundred others. Bluetooth seems the clear winner for smartphone-based products, but what about the other applications like home automation, logistics, smart metering, or dog tracking? Which protocol(s) will be the winner(s)? Which one will be natively supported on our Internet access gateways or even rolled-out worldwide? Will it be Thread, sponsored by Google itself? Or will it be another derivative of Bluetooth, due to its huge predominance? (The overall sales of Bluetooth-capable chips already exceed four times the human population on earth.) Or could it be one of the machine-to-machine variants of 3G/4G cellular standards being studied? Or perhaps it will be one of the solutions proposed by one of the many startups working on the technology? Or maybe it will be a completely new protocol that we’ll invent? I don’t know the answer, but the result will be the next game changer! (Robert is an electrical engineer and Circuit Cellar columnist. In 2003, he founded ALCIOM, an electrical engineering firm near Paris, France.)

CHRIS COULSTON: While tech will companies continue to evolve existing technologies to offer more features, with lower power and at a lower cost, I think that the most exciting and revolutionary technology is to be found in the Internet of Everything (IOE) concept. Hardware supporting the IOE offers up the tantalizing potential to free our designs from physical interconnects, giving our designs world wide access, allowing us to interact with our designs in real time, and allowing our design to access the almost unlimited diversity of services available on the Internet. I am excited to explore a design space that enables me to connect something trivial like my key-ring to the Internet. The Raspberry Pi was the first breakthrough with companies like Intel redefining the cutting edge with their Edison module. There are several limiters to the IOE concept including power consumption and standardization. As these issues are addressed, the potential of the IOE concept will only be limited to the creativity of engineers and makers everywhere. (Chris is a professor of electrical and computer engineering at Penn State, Behrend. He’s also technical reviewer for Circuit Cellar.)

GEORGE NOVACEK: Embedded controllers are essential components of automatic systems. Without  automation, many products could not even be manufactured. Machines, such as aircraft, medical equipment, power generators, etc. could not be operated without the assistance of smart control systems. Until some, not yet invented, technology makes electronics obsolete, the future of embedded controllers will remain bright. In the coming years, more and more engineers will be focusing on system design, while only the brightest ones will be developing microelectronic components for those systems—more sophisticated, more integrated, faster, smaller, hardened to environment, consuming less power. There continues to be a trend towards universal embedded controllers. These, equipped with the appropriate sensors and actuators and loaded with a particular application software, could be used for fly-by-wire, or for control of an industrial machinery or just about everything else. Design engineers need to be cautious not to put powerful, yet inexpensive controllers into new products just because it  can be done. There is already a proliferation of simple  consumer products equipped, without any sensible need, with microcontrollers. This often leads to lower reliability, shorter life and, because these products are usually not repairable, to greater cost of ownership and waste. (George is professional engineer and Circuit Cellar columnist who served as president of a multinational manufacturer of embedded control systems for aerospace applications.)

ED NISLEY: The rise of the Maker Movement changes everything in the embedded systems field: Makers take control over the devices in their lives, generally by repurposing embedded hardware in ways its designers never intended. The trend becomes clear when dirt-cheap USB TV tuners become software defined radios. Embedded systems must eventually sprout exposed (and documented!) interfaces, debugging hooks, and protocols, because collaboration with Makers who want to turn the box inside-out and build something better can enrich our world beyond measure. Excluding those people won’t work over the long term: just as DRM-encumbered music became unacceptable, welded-shut embedded systems will become historic curiosities. You can make it so! (Ed is an electrical engineer and long-time Circuit Cellar columnist and contributor.)

KEN DAVIDSON: Twenty-five years ago, while developing the Circuit Cellar Home Control System (HCS) II, our group created a series of interface boards that could be placed around the house and communicate using RS-485. Tons of discrete wire running throughout buildings was the norm at the time, and the idea of running just a single twisted pair between units was novel and exciting. This all predated inexpensive Ethernet and public Internet. Today, such distributed intelligence has only gotten better, smaller, and cheaper. With the Internet of Things (IoT) everybody is talking about, it’s not unusual to find a wireless interface and embedded intelligence right down to the level of a light bulb. There was an episode of The Big Bang Theory where the guys set up the apartment lights so they could be controlled from anywhere in the world. Everyone got a laugh when the “geeks” were excited when someone from Japan was blinking their lights. But the idea of such embedded intelligence and remote access continuing to evolve and improve truly is exciting. I look forward to the day in the not-too-distant future when such control is commonplace to most people and not just a geeky novelty. (Ken is an embedded software engineer who has been contributing to Circuit Cellar for years as an author and editor.)

These responses appear in Circuit Cellar 294 (January 2015).

Expanded Multi-Range Programmable DC Power Supply Offerings

B&K Precision recently announced the 9200 Series, which is its newest multi-range programmable DC power supply line. The series includes four 200- to 600-W models that can deliver power in any combination of the rated voltage and current up to the maximum output power of the supply. With voltage and current ranges up to 150 V and 25 A, the programmable DC power supplies are well suited for electronics manufacturing, R&D, and more.BK-9201_front

 

Multi-range power supplies provide greater flexibility than traditional power supplies. The supplies can provide any combination of higher voltage or higher current along a maximum power curve. This design helps save both bench space and cost by eliminating the need for having multiple power supplies on your workbench.

 

On the front panel, the 9200 Series features a high-resolution, 1 mV/0.1 mA display, output on/off control, and a handy user interface with numerical keypad, cursor keys, and rotary control knob for adjusting voltage and current settings. The power supplies also provide internal memory storage to save and recall up to 72 different instrument settings.

 

For programming and remote control, the 9200 Series offers list mode programming, remote sense, and standard USBTMC-compliant USB, RS-232, and GPIB interfaces supporting SCPI commands. Remote control software is provided for front panel emulation, execution of internal and external program sequences, and logging measurements via a PC. The application software can also be integrated with National Instrumnets’s Data Dashboard for LabVIEW app (available for Android and iOS), allowing users to create custom dashboards on smartphones and tablets for additional monitoring functions.

 

the 9200 Series models are all backed by a standard 3-year warranty and list at the following prices:

  • 9201 (60 V, 10 A, 200 W): $680
  • 9202  (60 V, 15 A, 360 W): $880
  • 9205 (60 V, 25 A, 600 W): $1,380
  • 9206  (150 V, 10 A, 600 W): $1,495

COMSOL Multiphysics 5.0 with App Builder and COMSOL Server to Run Simulation Apps

COMSOL provides simulation software for product design and research to technical enterprises, research labs, and universities throughout the world. Its flagship product, COMSOL Multiphysics, is a software environment for modeling and simulating any physics-based system and for building applications. A particular strength is its ability to account for coupled or multiphysics phenomena. Add-on products expand the simulation platform for electrical, mechanical, fluid flow, and chemical applications. Interfacing tools enable the integration of COMSOL Multiphysics simulation with all major technical computing and CAD tools on the CAE market.ComsolAcousticSimulationModelWeb

COMSOL’s Acoustics Module is designed specifically for those who work with devices that produce, measure, and utilize acoustic waves. Application areas include speakers, microphones, hearing aids, and sonar devices, to name a few. Noise control can be addressed in muffler design, sound barriers, and building acoustic applications.

Straightforward user interfaces provide tools for modeling acoustic pressure wave propagation in air, water, and other fluids. Dedicated modeling tools for thermoacoustics enable highly accurate simulation of miniaturized speakers and microphones in handheld devices. Its also possible to model vibrations and elastic waves in solids, piezoelectric materials, and poroelastic structures.

Multiphysics interfaces for acoustic-solid, acoustic-shell, and piezo-acoustics brings acoustic simulations to a new level of predictive power. By using COMSOL’s realistic simulations in 1D, 2D, or 3D, its possible to optimize existing products and design new products more quickly. Simulations also help designers, researchers, and engineers gain insight into problems that are difficult to handle experimentally. By testing a design before manufacturing it, companies save both time and money.

November 2014 marked the release of the revolutionary Application Builder, now available with COMSOL Multiphysics software version 5.0. The Application Builder, which allows COMSOL software users to build an intuitive interface to run any COMSOL model, has been very well received by the engineering community. COMSOL Multiphysics users are already building applications and exploring the benefits of sharing their models with colleagues and customers worldwide.

The Application Builder empowers the design process by allowing engineers to make available an easy-to-use application based on their COMSOL Multiphysics model. Included with the Windows operating system version of COMSOL Multiphysics 5.0, the Application Builder provides all the tools needed to build and run simulation apps. Any COMSOL Multiphysics model can be turned into an application with its own interface using the tools provided with the Application Builder desktop environment. Using the Form Editor, the user interface layout can be designed, while the Methods Editor is used for implementing customized commands. Based on the project at hand, engineering experts can now easily build a specialized application to share with their colleagues and customers that includes only the parameters relevant to the design of a specific device or product.

COMSOL Multiphysics 5.0 also brings three new add-on products to the extensive COMSOL product suite: the Ray Optics Module, the Design Module, and LiveLink for Revit.

For engineers working in application areas including building science, solar energy, and interferometers, the Ray Optics Module is an industry-leading simulation tool for analyzing systems in which the electromagnetic wavelength is much smaller than the smallest geometric detail in the model. Key features of the module include the ability to compute the trajectory of rays in graded and ungraded media, and the modeling of polychromatic, unpolarized and partially coherent light.

The Design Module expands the available toolset of CAD functionalities in the COMSOL product suite. The module includes the following 3D CAD operations: loft, fillet, chamfer, midsurface, and thicken, in addition to CAD import and geometry repair functionality.

Additionally, COMSOL is proud to offer LiveLink for Revit, which allows COMSOL users to interface with the building information modeling software from Autodesk. With LiveLink for Revit, users can seamlessly synchronize a geometry between LiveLink for Revit Architecture and COMSOL, allowing multiphysics simulations to be brought into the architectural design workflow.

Version 5.0 also introduces numerous enhancements to the existing functionalities of COMSOL Multiphysics. New features and updates have been added to the entire product suite, which includes over 25 application-specific modules for simulating any physics in the electrical, mechanical, fluid, and chemical disciplines.

COMSOL also announced the release of COMSOL Server, a new product developed specifically for running applications built with the Application Builder. Released earlier this year, the Application Builder allows COMSOL Multiphysics software users to build an intuitive interface around their COMSOL model that can be run by anyone—even those without prior simulation experience. COMSOL Server enables the distribution of applications, allowing design teams, production departments and others to share applications throughout an organization using a Windows-native client or web browser.

WiLink 8 Range of Wi-Fi and Bluetooth Modules

Texas Instruments has announced the WiLink 8 combo connectivity modules to support Wi-Fi in the 2.4- and 5-GHz bands. The new highly integrated module family offers high throughput and extended industrial temperature range with integrated Wi-Fi and Bluetooth. The modules complement TI’s PurePath Wireless audio ICs and TI’s SimpleLink Wireless Network Processors.WiLink8TexasInstruments

WiLink 8 modules are well-suited for power-optimized designs for home and building automation, smart energy applications, wearables, and a variety of other IoT applications. The WiLink 8 modules and software are compatible and preintegrated with many processors, including TI’s Sitara processors.

The WiLink8 family offers 2.4 and 5 GHz versions that are pin-to-pin compatible. With integrated Wi-Fi and Bluetooth, the WiLink 8 modules could be used for a variety of applications.

Features:

  • An extended temperature range of –40° to 85°C required for industrial applications
  • 5-GHz modules for high-performance solutions
  • Smart energy and home gateways, which offer Wi-Fi, Bluetooth and ZigBee coexistence, can manage multiple devices through Wi-Fi multi-channel multi-role (MCMR) capabilities
  • 1.4× the range and up to 100 Mbps throughput with TI’s WiLink 8 maximal ratio combining (MRC) and multiple-input and multiple-output (MIMO) technology
  • Optimization for low-power applications with low idle connect current consumption
  • Audio streaming for home entertainment applications with both Wi-Fi and dual-mode Bluetooth/Bluetooth low energy

The WiLink 8 modules complement several TI platforms to deliver system solutions for manufacturers including WiLink 8 module-based evaluation boards (2.4 GHz-WL1835MODCOM8 and 5 GHz -WL1837MODCOM8) that are compatible with the AM335x EVM and AM437x EVM. Additionally, the WiLink 8 modules, which offer Bluetooth and Bluetooth low energy dual-mode technology, are compatible with TI’s Bluetooth portfolio that allows developers to create a complete end-to-end application.

WiLink 8 evaluation boards (WL1835MODCOM8 and WL1837MODCOM8) are currently available. WiLink 8 modules production units will be available in Q1 2015 through TI authorized distributors starting at $9.99 in 1,000-unit volumes.

New PMR Common Platform Processor

CML Microcircuits recently released a PMR common platform processor to support digital/analog FDMA PMR/LMR and two-slot TDMA digital systems. As engineers have moved two-way radio from analog to digital, a variety of digital FDMA and TDMA PMR/LMR systems have emerged along with the on-going requirement for a radio platform to support legacy analog. Each system potentially has different requirements and specs down to the radio architecture level. The CMX7241/7341 PMR Common Platform Processor addresses the issue.CML - 7241_7341Image

The CMX7241/7341 provides a common platform that can deliver FDMA digital PMR/LMR, TDMA digital PMR/LMR and legacy analog. Based on CML’s FirmASIC component technology, a Function Image (FI) can be uploaded into the device to determine the CMX7241/7341’s overall functions and operating characteristics.

The first Function Image focuses on digital and analog FDMA PMR/LMR. It provides a comprehensive feature set including auxiliary functions to support the whole radio. When combined with CML’s CMX994 Direct Conversion Receiver IC, it presents a flexible, high-performance radio platform solution.

Important features:

  • Automatic analog/digital detection
  • Digital PMR/LMR (ETSI TS 102 658, TS 102 490 and EN 301 166 compliant; Embedded air interface physical and data link layers; and Mode 1, 2, and 3 operation)
  • Analog PMR/LMR (EN 300 086, EN 300 296 and  TIA-603-D compliant; Complete audio processing; Sub-audio signalling; Audio-band signalling; and MPT 1327 modem)
  • Function Image roadmap includes DMR, NXDN and PDT

Source: CML Microcircuits

Quad Output Programmable Universal PMIC

Exar Corp. recently announced the XR77129, a quad output programmable universal PMIC with an input operating voltage range of 6 to 40 V. Its patented control architecture is well suited for 40-V inputs using a 17-bit wide PID voltage mode VIN feed forward architecture. This controller offers a single input, quad output, step-down switching regulator controller with integrated gate drivers and dual LDO outputs. It can also monitor and dynamically control and configure the power system through an I2C interface. Five configurable GPIOs allow for fast system integration for fault reporting and status or for sequencing control.Exar-EX039_xr77129

The XR77129 can be configured to power nearly any FPGA, SoC, or DSP system with the use of Exar’s PowerArchitect and programmed through an I²C-based SMBus compliant serial interface. PowerArchitect 5.2 has been upgraded to support the additional capabilities of the XR77129 including output voltage ranges beyond the native 0.6 to 5.5 V with the use of external feedback resistors. The XR77129 wide input voltage range, low quiescent current of 450 µA (standby) and 4 mA (operating) make it a logical choice for a wide range of systems, including 18 to 36 VDC, 24 VDC or rectified AC systems used in the industrial automation and embedded applications.

The XR77129 is available now in an RoHS-compliant, green/halogen-free, space-saving 7 mm × 7 mm TQFN. It costs $9.95 in 1,000-piece quantities..

Summary of features:
•       6 to 40 V input voltage
•       Quad channel step-down controller
•       Digital PWM 105 kHz to 1.23 MHz operation
•       SMBus-compliant I²C interface
•       Supported by PowerArchitect 5.2 or later

Source: Exar

New EZ App Lynx Library for Creating Smart Bluetooth Sensors

CCS C-Aware IDE now includes the EZ App Lynx library (#include <EZApp.c>). Quickly create a Bluetooth wireless sensor, or controller, that may be viewed or managed on a paired mobile device using the EZ App Lynx Android app.EZ App Lynx Post_final

The free EZ App Lynx Library was created to shorten the design time for smart Bluetooth app development. With EZ App Lynx, and no required hardware or software expertise, the library removes the barriers to entry for smartphone app developers who want to take advantage of a growing number of Bluetooth enabled smartphones and tablets. The new library allows for any GUI, on the App, to be created at run time from a PIC program. The library offers many useful sensor interface components, which allow for: Status Bars, Gas Gauges, Sliders, Buttons, Text Fields, and more.

EZ App Lynx Library Features and Advantages:

  • No app design knowledge required
  • Source code libraries included with all CCS C Compilers
  • Included with maintenance update download

EZ App Lynx App:

  • Available for Android in Google Play Store (iOS available soon)
  • Build your own EZ App Lynx App in minutes with simple C library calls on the PIC
  • Quick and easy prototyping

Source: CCS

HumPRO Series Frequency-Hopping Digital Data Transceiver Module

Hummingbird platform is a low-cost complete wide-band transceiver with microcontroller module. The HumPRO Ssries wireless UART module is a completely integrated RF transceiver and processor designed to transmit digital data across a wireless link. It has a built-in frequency hopping over-the-air protocol that manages all of the transmission and reception functions. It takes data in on its UART and supplies the data out of a UART on the remote module.HUM-900-PRO

The HumPRO series modules have three addressing modes that support point-to-point and broadcast messages with 16- or 32-bit addresses. With no internal address or routing tables, the module does not limit the number of directly addressed or broadcast receivers within the operating range of the transmitter. Routing can be performed by an external microcontroller that is sized for memory and speed appropriate for the desired network size.

Specifications and features:

  • Low Cost: It uses advanced system on chip (SoC) technology to minimize the footprint and the number of components. The module is designed for high volume production, leading to a price that is nearly half that of similar modules, and making it cost competitive with discrete designs.
  • Robust: Built-in error detection and retransmission options create extremely robust point-to-point links for bi-directional data transmissions.
  • Frequency Hopping: The module has a FHSS protocol that typically locks in under 30 ms at 115 kbps and 60 ms at 9.6 kbps. This allows it to quickly wake up, send data and go back to sleep, saving power in battery-operated applications that have strict power budgets. It handles all protocol functions automatically.
  • Ease of Implementation: The user can configure a wide variety of settings through a standard UART interface. For point-point applications, the modules can be configured once, then send and receive data without need for further commands. For larger networks, commands support selective addressing and group broadcasting. The simple interface significantly reduces firmware development.
  • Addressing: All HumPRO modules have a unique 32-bit serial number that can be used as an address. Additional addressing modes support customer-assigned 16 or 32-bit source and destination addressing, enabling point-to-point and broadcast messages. Address masking by the receiving module allows for creating subnets. Advanced networks can be implemented with an external microcontroller.
  • Small Size: Like its namesake, Hummingbird modules are tiny. At 11.5 mm × 14 mm, it is less than one quarter the size of similar competitive modules.
  • Low Power: Linx designed the Hummingbird platform for battery powered applications. It operates as low as 2.0 V and has low transmit current of 40 mA, receive current of 25mA and standby current under 1 μA.
  • Ample Range: The HumPROTM outputs up to 10 dBm, resulting in a line-of-sight range of up to 1,600 m (1.0 mile), depending on the antenna implementation.
  • External Amplifiers: The module has control lines that allow it to work with an external PA and LNA for applications that need more system range.
  • Certification: The HumPRO Series is available in a non-certified version and in pre-certified versions with an RF connector or castellation connection.

Source: Linx Technologies