AC Tester Schematic Update

An error was found in one of the AC tester schematics that ran in Kevin Gorga’s June 2012 article, “AC Tester” (Circuit Cellar 263). As a reader indicated, T2 is disconnected in the published version of the schematic. An edited schematic follows.

Edited version of Figure 2 in K. Gorga’s June 2012 article, “AC Tester” (Source: Paul Alciatore)

The correction is now available on Circuit Cellar‘s Errata, Corrections, & Updates page.

DIY, Microcontroller-Based Battery Monitor for RC Aircraft

I’ve had good cause to be reading and perusing a few old Circuit Cellar articles every day for the past several weeks. We’re preparing the upcoming 25th anniversary issue of Circuit Cellar, and part of the process is reviewing the company’s archives back to the first issue. As I read through Circuit Cellar 143 (2002) the other day I thought, why wait until the end of the year to expose our readers to such intriguing articles? Since joining Elektor International Media in 2009, thousands of engineers and students across the globe have become familiar with our magazine, and most of them are unfamiliar with the early articles. It was in those articles that engineers set the foundation for the development of today’s embedded technologies.

Over the next few months, I will highlight some past articles here on CircuitCellar.com as well as in our print magazine. I encourage long-time readers to revisit these articles and projects and reflect on their past and present use values. Newer readers should not regard them as simply historical documents detailing outdated technologies. Not only did the technologies covered lead to the high-level engineering you do today, many of those technologies are still in use.

The article below is about Thomas Black’s “BatMon” battery monitor for RC applications (Circuit Cellar 143, 2002). I am leading with it simply because it was one of the first I worked on.

For years, hobbyists have relied on voltmeters and guesswork to monitor the storage capacity of battery packs for RC models. Black’s precise high-tech battery monitor is small enough to be mounted in the cockpit of an RC model helicopter. Black writes:

I hate to see folks suffer with old-fashioned remedies. After three decades of such anguish, I decided that enough is enough. So what am I talking about? Well, my focus for today’s pain relief is related to monitoring the battery packs used in RC models. The cure comes as BatMon, the sophisticated battery monitoring accessory shown in Photo 1.

Photo 1: The BatMon is small enough to fit in most RC models. The three cables plug into the model’s RC system. A bright LED remotely warns the pilot of battery trouble. The single character display reports the remaining capacity of the battery.

Today, electric model hobbyists use the digital watt-meter devices, but they are designed to monitor the heavy currents consumed by electric motors. I wanted finer resolution so I could use it with my RC receiver and servos. With that in mind, a couple of years ago, I convinced my firm that we should tackle this challenge…My solution evolved into the BatMon, a standalone device that can mount in each model aircraft (see Figure 1).

Figure 1: Installation in an RC model is as simple as plugging in three cables. Multiple point measurements allow the system to detect battery-related trouble. Voltage detection at the RC receiver even helps detect stalled servos and electrical issues.

This is not your typical larger-than-life Gotham City solution. It’s only 1.3″ × 2.8″ and weighs one ounce. But the BatMon does have the typical dual persona expected of a super hero. For user simplicity, it reports battery capacity as a zero to nine (0% to 90%) level value. This is my favorite mode because it works just like a car’s gas gauge. However, for those of you who must see hard numbers, it also reports the actual remaining capacity—up to 2500 mAH—with 5% accuracy. In addition, it reports problems associated with battery pack failures, bad on/off switches, and defective servos. A super-bright LED indicator flashes if any trouble is detected. Even in moderate sunlight this visual indicator can be seen from a couple hundred feet away, which is perfect for fly-by checks. The BatMon is compatible with all of the popular battery sizes. Pack capacities from 100 mAH to 2500 mAH can be used. They can be either four-cell or five-cell of either NiCD or NiMH chemistries. The battery parameters are programmed by using a push button and simple menu interface. The battery gauging IC that I used is from Dallas Semiconductor (now Maxim). There are other firms that have similar parts (Unitrode, TI, etc.), but the Dallas DS2438 Smart Battery Monitor was a perfect choice for my RC application (see Figure 2).

Figure 2: A battery fuel gauging IC and a microcontroller are combined to accurately measure the current consumption of an RC system. The singlecharacter LCD is used to display battery data and status messages.

This eight-pin coulomb counting chip contains an A/D-based current accumulator, A/D voltage convertor, and a slew of other features that are needed to get the job done. The famous Dallas one-wire I/O method provides an efficient interface to a PIC16C63 microcontroller…In the BatMon, the one-wire bus begins at pin 6 (port RA4) of the PIC16C63 microcontroller and terminates at the DS2438’s DQ I/O line (pin 8). Using bit-banging I/O, the PIC can read and write the necessary registers. The timing is critical, but the PIC is capable of handling the chore…The BatMon is not a good candidate for perfboard construction. A big issue is that RC models present a harsh operating environment. Vibration and less than pleasant landings demand that you use rugged electronic assembly techniques. My vote is that you design a circuit board for it. It is not a complicated circuit, so with the help of a freeware PCB program you should be on your way…The connections to the battery pack and receiver are made with standard RC hobby servo connectors. They are available at most RC hobby shops. You will need a 22-AWG, two-conductor female cable for the battery (J1), a 22-AWG, two-conductor male for the RC switch (J2), and a three-conductor (any AWG) for the Aux In (J3) connector…The finished unit is mounted in the model’s cockpit using double-sided tape or held with rubber bands (see Photo 2).

Photo 2: Here's how the battery monitor looks installed in the RC model helicopter’s cockpit. You can use the BatMon on RC airplanes, cars, and boats too. Or, you could adapt the design for battery monitoring applications that aren’t RC-related.

Thomas Black designs and supports high-tech devices for the consumer and industrial markets. He is currently involved in telecom test products. During his free time, he can be found flying his RC models. Sometimes he attempts to improve his models by creating odd electronic designs, most of which are greeted by puzzled amusement from his flying pals.

The complete article is now available.

Q&A: Ayse Kivilcim Coskun (Engineer, BU)

Ayse Kivilcim Coskun’s research on 3-D stacked systems has gained notoriety in academia, and it could change the way electrical engineers and chip manufacturers think about energy efficiency for years to come. In a recent interview, the Boston University engineering professor briefed us on her work and explained how she came to focus on the topics of green computing and 3-D systems.

Boston University professor Ayse Kivilcim Coskun

The following is an excerpt from an interview that appears in Circuit Cellar 264 (July 2012), which is currently on newsstands.

NAN: When did you first become interested in computer engineering?

AYSE: I’ve been interested in electronics since high school and in science and physics since I was little. My undergraduate major was microelectronics engineering. I actually did not start studying computer engineering officially until graduate school at University of California, San Diego. However, during my undergraduate education, I started taking programming, operating systems, logic design, and computer architecture classes, which spiked my interest in the area.

NAN: Tell us about your teaching position at the Electrical and Computer Engineering Department at Boston University (BU).

AYSE: I have been an assistant professor at BU for almost three years. I teach Introduction to Software Engineering to undergraduates and Introduction to Embedded systems to graduate students. I enjoy that both courses develop computational thinking as well as hands-on implementation skills. It’s great to see the students learning to build systems and have fun while learning.

NAN: As an engineering professor, you have some insight into what excites future engineers. What “hot topics” currently interest your students?

AYSE: Programming and software design in general are certainly attracting a lot of interest. Our introductory software engineering class is attracting a growing number of students across the College of Engineering every year. DSP, image processing, and security are also hot topics among the students. Our engineering students are very keen on seeing a working system at the end of their class projects. Some project examples from my embedded systems class include embedded low-power gaming consoles, autonomous toy vehicles, and embedded systems focusing on healthcare or security applications …

NAN: How did you come to focus on energy efficiency and thermal challenges?

AYSE: Energy efficiency has been a hot topic for embedded systems for several decades, mainly due to battery-life restrictions. With the growth of computing sources at all levels—from embedded to large-scale computers, and following the move to data centers and the cloud—now energy efficiency is a major bottleneck for any computing system. The focus on energy efficiency and temperature management among the academic community was increasing when I started my PhD. I got especially interested in thermally induced problems as I also had some background on fault tolerance and reliability topics. I thought it would be interesting to leverage job scheduling to improve thermal behavior and my advisor liked the idea too. Temperature-aware job scheduling in multiprocessor systems was the first energy-efficiency related project I worked on.

NAN: In May 2011, you were awarded the A. Richard Newton Graduate Scholarship at the Design Automation Conference (DAC) for a joint project, “3-D Systems for Low-Power High-Performance Computing.” Tell us about the project and how you became involved.

AYSE: My vision is that 3-D stacked systems—where multiple dies are stacked together into a single chip—can provide significant benefits in energy efficiency. However, there are design, modeling, and management challenges that need to be addressed in order to simultaneously achieve energy efficiency and reliability. For example, stacking enables putting DRAM and processor cores together on a single 3-D chip. This means we can cut down the memory access latency, which is the main performance bottleneck for a lot of applications today. This gain in performance could be leveraged to run processors at a lower speed or use simpler cores, which would enable low-power, high-performance computing. Or we can use the reduction in memory latency to boost performance of single-chip multicore systems. Higher performance, however, means higher power and temperature. Thermal challenges are already pressing concerns for 3-D design, as cooling these systems is difficult. The project focuses on simultaneously analyzing performance, power, and temperature and using this analysis to design system management methods that maximize performance under power or thermal constraints.

I started researching 3-D systems during a summer internship at  the Swiss Federal Institute of Technology (EPFL) in the last year of my PhD. Now, the area is maturing and there are even some 3-D prototype systems being designed. I think it is an exciting time for 3-D research as we’ll start seeing a larger pool of commercial 3-D stacked chips in a few years. The A. Richard Newton scholarship enabled us to do the preliminary research and collect results. Following the scholarship, I also received a National Science Foundation (NSF) CAREER award for designing innovative strategies for modeling and management of 3-D stacked systems.

The entire interview appears in Circuit Cellar 264  (July 2012).

DesignSpark chipKIT Challenge 2012 Winners Named

The results for the DesignSpark chipKIT Challenge are now final. Dean Boman won First Prize for his chipKIT-based Energy Monitoring System, which provides users real-time home electrical usage data. A web server provides usage tracking on a circuit-by-circuit basis. It interfaces with a home automation system for long-term monitoring and data logging.

Dean Boman's Energy Monitoring System (Source: D. Boman)

Second prize went to Raul Alvarez for his Home Energy Gateway consumption monitor, which features an embedded gateway/web server that communicates with “smart” devices.

Raul Alvarezs Home Energy Gateway (Source: R. Alvarez)

Graig Pearen won Third Prize for his PV Array Tracker (Sun Seeker) project, which tracks, monitors, and adjusts PV arrays based on weather conditions.

Graig Pearen's PV Array Tracker (Source: G. Pearen)

Click HERE for a list of all the winners. You can review their project abstracts, documentation, schematics, diagrams, code, and more.

Participants in the competition were challenged develop innovative, energy-efficient designs with eco-friendly footprints. Entries were required to include an extension card developed using the DesignSpark PCB software tool and the Microchip Max32 chipKIT development board.

According to the documentation on the design challenge site:

The chipKIT™ Max32™ development platform is a 32-bit Arduino solution that enables hobbyists and academics to easily and inexpensively integrate electronics into their projects, even if they do not have an electronic-engineering background.

The platform consists of two PIC32-based development boards and open-source software that is compatible with the Arduino programming language and development environment. The chipKIT™ hardware is compatible with existing 3.3V Arduino shields and applications, and can be developed using a modified version of the Arduino IDE and existing Arduino resources, such as code examples, libraries, references and tutorials.

The chipKIT™ Basic I/O Shield (part # TDGL005) is compatible with the chipKIT™ Max32™ board, and offers users simple push buttons, switches, LEDs, I2C™ EEPROM, I2C temperature sensor, and a 128 x 32 pixel organic LED graphic display.

 

Click HERE for a list of all the winners. You can review their project abstracts, documentation, schematics, diagrams, code, and more.

Circuit Cellar/Elektor Inc. is the Contest Administrator.

The Renesas RL78 for Low-Power Applications

Renesas Technology announced in late March he start of a design challenge for engineers around the world: develop an innovative, low-power application using the RL78 MCU and IAR Systems toolchain. To get started, you need to familiarize yourself with the RL78. Clemens Valens, Editor-in-Chief of Elektor online, introduces the RL78 in a comprehensive “The RL78 Microcontroller: An MCU Family for Low-Power Applications” (Circuit Cellar 261, 2012).

I’ve worked with Valens in various occasions, and had the pleasure of meeting him in 2011. He’s truly “an engineer’s engineer”: extremely embedded tech savvy, well-read, and inquisitive. Furthermore, I edited Circuit Cellar articles Valens wrote about diverse design projects, such as a virtual instrument interface and a scrolling LED message board. Thus, it’s clear to me that Valens understands the importance of designing high-quality, energy-efficient, systems—and doing so within budget. I trust you’ll find his introduction to the RL78 insightful and immediately applicable.

The RL78 Microcontroller: An MCU Family for Low-Power Applications

By Clemens Valens (Circuit Cellar 261, 2012)

The low-power 8/16-bit microcontroller (MCU) market is a bit of a warzone with several MCU manufacturers proposing “the industry’s lowest power solution.” In a YouTube video, Texas Instruments boasts a best active figure of 160 μA/MIPS for their MSP430 family. In application note AN1267, Microchip Technology claims 110 μA at “1 MHz Run” for their PIC16LF72X. And Renesas Electronics announced 70 μA at “1-MHz normal operation” on their RL78 product website.[1, 2, 3] The absence of justification on how exactly these figures were obtained makes comparing them rather useless. But then again, you don’t really have to because, as most low-power developers know from experience, if you don’t get the hardware and software design right, you will never attain the promised 20-year battery lifetime no matter how low the MCU’s active, sleep, or standby current may be. In this article, I will take a closer look at Renesas’s quickly expanding RL78 family to see what they offer that may help you create a low-power design.

Photo 1 - The Renesas RL78

THE RL78 FAMILY

The RL78 family of 16-bit MCUs currently has two branches, “generic” and “application specific,” but a third “display” branch is forthcoming. The generic branch contains the subfamilies G12, G13, and G1A, all based on the 78K core, and the G14, which is based on the R8C core. In the application-specific branch there is the 1A and F12. I am not sure about their core origins as these products are still very new and, at the time of writing, documentation is missing. It doesn’t really matter; from now on it is the new RL78 core for all. Since they share the same core, I will concentrate on the G13 for which I have a nice evaluation board (see Photo 1 and “The Renesas Demonstration Kit for RL78” sidebar).

Sidebar: Renesas Demonstration Kit

RL78/G13

This family comes in a large number of variants (I counted 182), with devices having from 20 up to 128 pins (see Figure 1). Note that the parts themselves are labelled R5F10xx. The differences between all these variants are, besides the package type, the amounts of flash memory (program and data) and RAM. Program flash memory starts at 16 KB and currently ends at 512 KB, data flash sizes can be 0, 4, or 8 KB and RAM is 2 KB for the small devices and up to 32 KB for the big ones.

Figure 1 - Diagram of 128-pin RL78/G13 devices

The CPU is 16-bit, but the internal memory architecture is 8 bit. Its 32 general-purpose registers are organized in four banks of eight and can be used as 8- or 16-bit registers. The memory-mapped special function registers (SFRs) that control the on-chip peripherals can be addressed per bit, per byte, or as 16-bit registers, depending on the register. A second set of SFRs, the extended or second SFRs, are available too, but they need longer instructions to be accessed.

For those who need to squeeze the maximum out of MCU performance, it may be interesting to know that the CPU offers a short addressing mode enabling you to access a page of 256 bytes with a minimum amount of code.

The maximum clock frequency of the processor is 32 MHz, but the hardware user’s manual, which is almost 1,100 pages, interestingly also boasts about the ultra-low-speed capabilities of the processor as it can run from a 32.768-kHz clock.

The RL78 core features 15 I/O ports, most of which are 8-bit wide. Port 13 is 2-bit wide and ports 10 and 15 are 7-bit wide. The port pins that are actually available depend on the device. Inputs and outputs are highly configurable. Inputs can be analog, CMOS, or TTL. Outputs can be CMOS or N-channel open drain. Pull-up resistors are available too. The exact configuration possibilities depend on the port pin, so consult the datasheet. Because of the many configuration options, it is possible to use the MCU in multi-voltage systems without level-shifting circuitry except for the occasional external pull-up resistor. The chip can be powered from 1.6 V to 5.5 V, the core itself runs from 1.8 V provided by an internal voltage regulator.

TIME MANAGEMENT

Several options are available for the MCU clock. When clock precision is not too important, the MCU can be run from its internal clock, up to 32 MHz, otherwise it is possible to connect an external crystal, resonator, or oscillator. An internal low-speed clock (15 kHz) is also available, but not for the CPU, only for the watchdog timer (WDT), the real-time clock (RTC), and the interval timer.

The timers of the RL78 are flexible and offer many functions. Depending on the pin size of the device, you can have up to 16 16-bit timers, grouped in two arrays of eight. Each timer (called a “channel”) can function as an interval timer, square-wave generator, event counter, frequency divider, pulse-interval timer, pulse-duration timer, and delay counter. For even more possibilities, timers can be combined to create monostable multivibrators or to do pulse-width modulation (PWM). This way, up to seven PWM signals can be generated from one master timer. If you need more timers but resolution is less important, you can split some 16-bit timers in two 8-bit timers (this is not possible with all timers). Timer 7 of array 0 is extra special as it features local interconnect network (LIN) network support (see below).

Aside from date and time keeping with alarms, the RTC also provides constant period interrupts at 2 Hz and 1 Hz and also every minute, hour, day, or month. A 1-Hz output is available on devices with 40 or more pins. For extra precision, the RTC offers a correction register for fine tuning the 32,768-kHz clock. Unsurprisingly, the RTC continues operation when the MCU is stopped.

Now that I mentioned Stop mode, a special interval timer peripheral enables wakeup from this mode at periodic intervals. This timer is also used for the analog-to-digital converter’s (ADC’s) Snooze mode. More on that later. With a clock frequency of 32,768 Hz, the lowest interval rate is 8 Hz (0.125 ms).

Yet another time-related peripheral on the RL78 is the buzzer controller (not available on 20-pin devices). This is a clock output destined at IR comms carrier generation, to clock other chips in a system or to produce sound from a buzzer. A gate bit enables modulation of this output in such a way that pulses always have the same width.

Finally, a WDT completes the timing peripherals. It has a special Window mode that limits the time frame during which you can reset the watchdog to a fraction of the watchdog interval (50%, 75%, or 100%). Resetting the watchdog counter outside the window results in a reset. The window is open in the second part of the interval. An interrupt can be generated when the WDT reaches 75% of its time-out value, (i.e., when the watchdog reset window is known to be open in all cases). Figure 2 illustrates the mechanism.

Figure 2 - Trying to reset the watchdog counter when the window is closed results in an internal reset signal

ADC

The ADC is of the 10-bit successive approximation type and can have up to 26 inputs. Several triggering options are provided, hardware and software, where hardware triggering means triggering by a timer module (timer channel 1 end of count or capture, interval timer, or RTC). The time it takes to do a conversion depends partly on the triggering mode. When input stabilization is not too much of an issue (i.e., when you don’t switch inputs) you can achieve conversion times of just over 2 μs.

Two registers enable comparing the ADC’s output to maximum and minimum values, producing an interrupt when the new value is either in or out of bounds. This function is also available in Snooze mode. In this mode, the processor itself is stopped and consumes very little power, but ADC conversions continue under control of the hardware trigger. When a conversion triggers an ADC interrupt, the processor can then wake up from Snooze mode and resume normal operation.

COMMUNICATIONS

The RL78 features multifunction serial units. The devices with 25 pins or less have one such unit, the others have two. Only serial unit 2 provides LIN bus support.

A serial unit can function in asynchronous UART mode, in synchronous CSI mode (three-wire bus with clock, data in and data out signals, master and slave mode supported), and in simplified (master-only) I²C mode. Again, depending on the device, you can have up to four UARTs or eight CSI and/or simplified I²C ports. Of course a mix is also possible. Full I²C is possible with the specialized I²C unit.

UART0 and UART2, CSI00 and CSI20 provide Snooze mode functionality similar to the ADC. In Snooze mode, these ports can be made to wake up on the arrival of incoming data without waking up the CPU. If the received data is interesting enough, it is also possible to wake up the CPU.

LIN communications are possible with UART2 together with Timer 7 of Array 0. The LIN bus is an inexpensive alternative to the CAN bus in automotive systems to control simple devices like switches, sensors, and actuators. LIN only uses one wire and is rather low speed (20 Kbps maximum). The timer takes care of the LIN synchronization issues and the UART performs the (de)serialisation of the data.

Full blown I²C communication is possible with the specialized I²C peripheral IICA. The 80-pin and more devices have two channels, the others only one. Communication speeds up to 20 MHz are permitted to enable I²C “fast mode” (3.5 MHz) and “fast mode plus” (10 MHz). This module is capable of waking up the CPU from Stop mode.

MATH ACCELERATORS

Of interest is the hardware multiplier and divider module intended for filtering and FFT functions. This module is capable of 16 × 16 bits signed and unsigned multiplications and divisions producing 32-bit results. It can also do 16 × 16 bit multiply-accumulate. We are talking about a module here, not an instruction, meaning that you have to load the operands yourself in special registers and get the result from yet another. The multiplication itself is done in one clock cycle, a division takes 16. The accumulate operation adds another cycle.

Another special math function is the binary-coded decimals (BCD) correction register that enables you to easily transform binary calculation results into BCD results.

DIRECT MEMORY ACCESS

To speed up data transport without loading the CPU, the RL78 core features direct memory access (DMA), up to four channels. DMA transfers up to 1,024 words of data (8 or 16 bit) to and from SFRs and RAM and they can be started by a range of interrupts (e.g., ADC, serial, timer). Although DMA transfers are done in parallel with normal CPU operation, it does slow down the CPU. For time-critical situations, it is possible to put a DMA transfer on hold for a number of clock cycles and let the CPU finish its job first.

INTERRUPTS

Interrupts are pretty standard on the RL78 and many sources are available. The “key interrupt” function on the other hand is less common. It provides up to eight (depending on the device, you guessed it) key or push button inputs that are ORed together to generate an interrupt on a key press (active low).

OPERATING MODES & SECURITY

Besides the aforementioned Stop and Snooze modes, the RL78 also provides a Halt mode. In this mode, the CPU is stopped but the clocks keep running, making a fast resume possible. In Stop mode, the clocks are stopped too reducing power consumption more than in Halt mode. Snooze mode is like Stop mode, but with one or more peripherals in a snoozing state, ready to wake up when something interesting happens. Interrupts can be used to wake up from Snooze, Stop, or Halt mode. A reset usually works too.

Reset, by the way, can have seven origins, three of which are related to safety functions: illegal instruction, RAM parity, and illegal memory access. Two others involve the power supply: power-on reset (POR) and low-voltage detection (LVD). All these reset options are needed to conform to the International Electrotechnical Commission (IEC) 60730-1 (“Automatic Electrical Controls for Household and Similar Use; Part 1: General Requirements”) and IEC 61508-SER (“Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems”) safety standards. Since the RL78 is compliant, it also implements flash memory CRC checking, protections to prevent RAM and SFRs to be modified when the CPU stops functioning, an oscillator frequency-detection circuit, and an ADC self-test function.

The hardware used for the flash memory CRC check is also available as a general-purpose CRC module for user programs. It implements the standard CCITT CRC-16 polynomial (X^16 + X^12 + X^5 + 1).

The RAM guard function protects only up to 512 bytes, so be careful where you put your sensitive data.

FLASH & FUSES

Those familiar with the fuse bytes of PIC and AVR processors will be happy to know that the RL78 contains four of them, the option bytes that configure such things as the WDT, low-voltage detection, flash memory modes, clock frequencies, and debugging modes.

Flash memory is divided into two parts, program memory and data memory, and it can be programmed in-circuit over a serial interface. A boot partition is available too. This partition uses a kind of ping-pong mechanism called “boot swapping” to ensure that a valid bootloader is always programmed into the boot partition so that even power failures during bootloader programming will not harm the boot partition. A flash window function protects the memory against unintentionally reprogramming parts of it.

SOUNDING OFF

This concludes our voyage through the Renesas RL78 core. As you have seen, the RL78 offers many interesting peripherals all combined in a flexible low-power optimized design. Thanks to the integrated oscillator and other functions, an RL78 MCU can be used with very little external hardware, enabling inexpensive and compact designs. Once you master its Snooze mode and your low-power design skills, you can use this MCU family in battery-operated metering applications, for instance, but I am sure you can think of something more surprising.

Clemens Valens (c.valens@elektor.fr) is Editor-in-Chief of Elektor Online. He has more than 15 years of experience in embedded systems design. Clemens is currently interested in sound synthesis techniques, rapid prototyping, and the popularization of technology.

REFERENCES

[1] Texas Instruments, Inc., “Ultra-Low Power MSP430 – The World’s Lowest Power MCU,” 201.

[2] Microchip Technology, Inc., “AN1267: nanoWatt and nanoWatt XLP Technologies: An Introduction to Microchip’s Low-Power Devices,” 2009.

[3] Renesas Electronics Corp., “RL78 Family,” www.renesas.com/pr/mcu/rl78/index.html.

RESOURCES

International Electrotechnical Commission (IEC), “60730-1, Automatic Electrical Controls for Household and Similar Use; Part 1: General Requirements,” 2002.

———, “61508-SER, Functional Safety of Electrical/

Electronic/Programmable Electronic Safety-Related Systems,” 2010.

Renesas Electronics Corp., Renesas Rulz, “RL78/G13 Demonstration Kit,” www.renesasrulz.com/community/demoboards/rdkrl78g13.

For more information about the RL78 Family of microcontrollers, visit www.renesas.com.

For information about the 2012 Renesas RL78 Green Energy Challenge (in association with Elektor & Circuit Cellar), go to www.circuitcellar.com/RenesasRL78Challenge.

This article appears in Circuit Cellar 261 (April 2012).