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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

Highly Accurate 60-V I²C Battery Cell Monitor

Linear Technology Corp. recently introduced the LTC2944 multicell battery monitor, which makes direct measurements of 3.6-to-60-V battery stacks. No level shifting circuitry on the supply and measurement pins is required to interface with multicell voltages, so total current consumption is minimized and measurement accuracy is preserved. Well suited for multicell applications (e.g., electric vehicles, ebikes, and battery backup systems), the LTC2944 is a true high voltage battery monitor that measures charge, voltage, current and temperature to 1% accuracy, the essential parameters required to accurately assess battery state of charge (SoC).Linear Technology LTC2944

Battery current is measured by monitoring the voltage across an external, high-side sense resistor and integrating this information to infer charge. A bidirectional analog integrator accommodates either current polarity (battery charge or discharge). A programmable prescaler supports a wide range of battery capacities. Charge, voltage, current, and temperature information are communicated to the host system over an I²C/SMBus-compatible two-wire interface that is also used to configure the battery monitor. The host can program high and low thresholds for all measured parameters, which if tripped, signal an alert using either the SMBus alert protocol or by setting a register flag.

The LTC2944’s features, specs, and benefits:

  • Measures accumulated battery charge and discharge
  • 3.6-to-60-V Operating range for multicell applications
  • 14-Bit ADC Measures voltage, current, and temperature
  • 1% Charge, voltage, and current accuracy
  • ±50-mV Sense voltage range
  • High-side sense
  • I²C/SMBus Interface
  • Configurable alert output/charge complete input
  • Quiescent current less than 150 μA
  • Small eight-pin 3 mm × 3 mm DFN package

The LTC2944 is available in a small RoHS-compliant, eight-pin 3 mm × 3 mm DFN package. Pricing starts at $2.85 each in 1,000-piece quantities.

Source: Linear Technology

WattUp Wireless Power RF-Transmit IC

Dialog Semiconductor and Energous Corp. recently announced the availability of the DA4100 RF-transmit integrated circuit (IC), which is intended to simplify the implementation of WattUp wireless power transmitter systems. The WattUp wireless power RF-transmit IC integrates the ARM Cortex-M0+, RF transmitter, and power management functionality into a single 7 mm × 7 mm IC. In addition, it features on-chip DC-DC conversion and software, which provides seamless integration to Dialog’s SmartBond family of low-power BLE SoCs. The new IC minimizes required board space, which enables ultra-small charging transmitters and simplifies WattUp’s wireless power transmitter system implementation. DA4100 WattUp wireless power RF-transmit IC evaluation kits are now available.

Source: Dialog Semiconductor

PW1-928 RF Data Transceiver Module

The PW1-928 RF transceiver module is intended for the reliable bidirectional transfer of digital data over distances of over 300′ in cluttered urban environments (more than half a mile in true line of sight). The module—which operates in the 902-to-928-MHz frequency band—generates a nominal 7 dBm into a 50-Ω load and achieves an outstanding RX sensitivity of –112 dBm.Lemos can 1

The module uses the industry standard LoRa direct sequence chirp spreading protocol combined with a proprietary data structure to both simplify user implementation and to significantly improve packet transmission reliability. It has a Universal Asynchronous Receiver Transmitter (UART) serial interface that can be directly connected to typical microcontrollers, RS-232 converters, or USB adaptors. The module automatically handles all radio functions resulting in a true UART-to-antenna wireless link. Configuration setup is also accessed through the UART interface.

The module is well suited for a variety of applications, including asset tracking, remote data logging, and industrial/home automation. Features:

  • True “asynchronous UART to antenna” solution
  • Direct sequence (chirp) spread spectrum
  • 9.6-kbps user payload data rate
  • Uses highly robust augmented LoRa protocol
  • Low power standby and TX-from-standby modes
  • Adjustable output power
  • User programmable address and channel-group
  • 3.3-V logic I/O
  • Digital RSSI (read via serial port)

Source: Lemos International

Arduino-Based Liquid Level-Sensing Hardware

SST Sensing and Sparkfun recently developed an easy-to-use solution for single-point liquid detection using infrared technology. Highly accurate and reliable, the solution features an Optomax Digital liquid level switch, which is connected to an Arduino board via the TTL output and powered by the 5-V source. SST Sparkfun

Whether you’re a professional engineer or DIYer, you’ll find it easy to program the Arduino’s LEDs to indicate when the sensor is immersed in liquid (and thus determine if the liquid level is too high or low). The compact switch lends itself will to space-constrained applications. With long cabling, you can place the sensor near a liquid without putting the other electronics at risk. Since this is an optical solution, you can avoid a variety of issues (e.g., jamming and wear and tear) and ensure long operational lifespan.

SST offers the liquid level switch in a robust housing tip with either a Polysulfone or Trogamid construction (depending on the particular application requirements). The complete solution has an operational temperature range of –25°C to 80°C.

Source: SST

Flowcode (Part 5): Ghost Technology

Flowcode features several debugging tools designed to help you develop your programs, get them working reliably, and eliminate any bugs. The fifth article in this series deals with the debugging features. Download the article

In the first article in this series, you were introduced to Flowcode 7, flowchart-driven electronic IDE that enables you to produce hex code for more than 1,300 different microcontrollers, including PIC8, PIC16, PIC32, AVR, Arduino, and ARM. The second article detailed how to get working with displays in Flowcode. The third article detailed some of the more complex communications components, Modbus and DMX. The fourth article detailed the Matrix Industrial Automotive Controller (MIAC).

Want a Free Trial and/or Buy Flowcode 7? Download Now

Flowcode is an IDE for electronic and electromechanical system development. Pro engineers, electronics enthusiasts, and academics can use Flowcode to develop systems for control and measurement based on microcontrollers or on rugged industrial interfaces using Windows-compatible personal computers. Visit www.flowcode.co.uk/circuitcellar to learn about Flowcode 7. You can access a free version, or you can purchase advanced features and professional Flowcode licenses through the modular licensing system. If you make a purchase through that page, Circuit Cellar will receive a commission.

Multiphase 12-A DC-DC Buck Converter

Dialog Semiconductor recently announced the DA9210-A power management IC (PMIC). A multiphase, automotive-grade, 12A DC-DC buck converter, the DA9210-A supplies the high current core rails of microprocessor devices. Designed for automotive applications, the DA9210-A is optimized for the supply of CPUs and GPUs and can support load currents of up to 12 A in single-chip configuration and 24 A in dual parallel configuration.

The PMIC’s features, benefits, and specs:

  • High efficiency over a wide output range
  • Accepts input voltages from 2.8 to 5.5 VDC
  • Delivers an output voltage between 0.3 and 1.57 V, with ±2.5% output voltage accuracy
  • 3-MHz nominal switching frequency
  • Fully AEC-Q100 grade 3 qualified
  • 42 WL-CSP package

Source: Dialog Semiconductor

BitScope Blade for Raspberry Pi

element14 recently announced the availability of the new BitScope Blade range, which enables you to power and mount multiple Raspberry Pi computers. You can use every Blade with simple plug packs, 12-V batteries, solar power systems, low-cost UPSes, and passive power over Ethernet (PoE) solutions. You can use them in a variety of ways: on a desktop, wall mounted, or in racks for large-scale deployment. Blades offer full access to Raspberry Pi I/O for displays, cameras, keyboards, expansion boards, and peripherals including BitScopes, Raspberry Pi HATs, and the Raspberry Pi 7” touchscreen display.

Designed for building scalable computing solutions (e.g., stand-alone servers, private clouds, and Industrial IoT systems), the BitScope Blade is available in three editions based on the number of Raspberry Pi boards mounted.

The BitScope Blade Uno is a flexible power and mounting solution for one Raspberry Pi computer and optional HAT. It is the perfect computing platform for makers, students and engineers using the Raspberry Pi.

The BitScope Blade Duo is a desktop, rack or wall mountable power and mounting solution for a pair of Raspberry Pi computers, ideal for building a reliable stand-alone desktop and server system with the Raspberry Pi.

The BitScope Blade Quattro is a desktop, rack, or wall-mountable power and mounting solution for four Raspberry Pi computers. It’s ideal for creating computer clusters, private clouds, or build farms with the Raspberry Pi.

Source: element14

Low-Cost Tech for Large-Area OLEDs

CSEM and Sefar AG recently announced the development of an affordable method for increasing the attractiveness of OLEDs for lighting for buildings as well as consumer electronics.Thanks to a project supported by the Swiss Confederation (CTI project), the CSEM and Sefar solution is transparent but still highly conductive. The flexible electrodes are made of fabric substrates comprising flexible metallic wires and polymeric fibers that are woven together in a highly transparent and flexible polymer. These fabric substrates (SEFAR TCS Planar) are manufactured using low-cost, high-throughput processes under standard ambient clean room conditions. CSEM

The substrate is coated with a thin-film (tens of nanometers) layer of a solutionprocess conductive polymer. The high electrical conductivity of the metal wires in the fabric substrate ensures that the electrode displays high conductivity over long distances, even with an ultra-thin layer of the conductive polymer.

Source: CSEM

Electrical Engineering Crossword (Issue 319)

The answers to the Circuit Cellar 319 crossword puzzle are now available.319 Crossword


  1. DYNE—10–5 N
  2. PICOAMP—10–12 A
  3. HANDSHAKE—Exchange of signals to start or finish a function
  4. LATENCY—Delay
  5. GAUSSMETER—Measures gap energy
  7. CONE—1/3Bh
  8. ANGSTROM—1 = 10–10 m


  1. ENDOTHERMIC—Absorbs heat
  2. YAGI—An antenna that enables directional communication using electromagnetic waves
  3. VOLTA—Invented the voltaic pile
  4. BAR—10<sup>5</sup> Pascals
  5. SAWTOOTH—Slow rise, fast fall
  6. EULER—E<sup>ipi</sup> + 1 = 0
  7. INTERCEPTPOINT—A measure of the inter-modulation performance of an RF devices
  8. VAR—Volt amp reactive
  9. LUX—Light intensity
  11. TRIPLEPOINT—Water at 0.01°C
  12. CENTROID—The center of mass

Near-Zero-Power Voice-Activation for Battery-Powered Devices

Vesper, DSP Group and Sensory have demonstrated a turnkey development platform that boasts the lowest overall power consumption for far-field always-listening voice interfaces. The DSP Group also recently unveiled its new DBMD5 audio SoC built to drive clearer human-machine voice interactions.Vesper Sensory

The Vesper-DSP Group-Sensory integrated development platform features Sensory’s voice algorithms, enabling ultra-low-power consumer electronics that wake at voice input. This platform is the first to achieve overall power consumption low enough to enable battery-powered always-listening far-field systems.

The new development platform integrates Vesper’s VM1010 wake-on-sound piezoelectric MEMS microphone with DSP Group’s DBMD4, an ultra-low-power, always-on voice and audio processor based on Sensory’s Truly Handsfree voice control embedded algorithms. The platform gives developers the ability to initiate voice processing through Sensory’s wake-up word technology, which ensures that only a specific trigger word activates the device.

DSP Group’s new DBMD5 audio SoC built to drive clearer human-machine voice interactions in microphone-equipped devices. By leveraging DBMD5 with HDClear technology to support hands-free device control, manufacturers can now add a voice-user interface (VUI) to their products for accuracy in high-noise environments along with control over voice triggers and barge-in capabilities.

The DBMD5 solution offers sophisticated voice enhancement algorithms, including echo cancellation, noise suppression, beam forming and far-field support. Its programmable dual-core DSP supports digital and analog microphones, incorporating various application processor interfaces—such SPI, I2C, UART, and SLIMbus—while a complete suite of drivers allow rapid development and fast time-to-market.

Source: Vesper

Transform IoT Audio, Voice, and Video Interactions

NXP Semiconductors (now part of Qualcomm) recently introduced the new i.MX 8M family of applications processors specifically designed to meet increasing audio and video system requirements for smart home and smart mobility applications such as over-the-top (OTT) set-top boxes, digital media adapters, surround sound, sound bars, A/V receivers, voice control, voice assistance, digital signage, and general-purpose human machine interface (HMI) solutions.NXP-iMX8M-FS

The concept of the smart home is expanding rapidly, heightening consumers’ expectations for audio and video entertainment and transforming the requirements for consumer electronics devices. NXP’s i.MX 8M family addresses the major inflection points currently underway in streaming media: voice recognition and networked speakers in audio, and the move to 4K High Dynamic Range (HDR) and the growth of smaller, more compact form factors in video.

NXP’s i.MX 8M family of processors has up to four 1.5-GHz ARM Cortex-A53 and Cortex-M4 cores, flexible memory options and high-speed connectivity interfaces. The processors also feature full 4K UltraHD resolution and HDR (Dolby Vision, HDR10 and HLG) video quality, the highest levels of pro audio fidelity, up to 20 audio channels and DSD512 audio. The i.MX 8M family is tailored to streaming video devices, streaming audio devices and voice control applications.

Capable of driving dual displays, the new devices include:

  • The i.MX 8M Dual/i.MX 8M Quad, which integrates two or four ARM Cortex-A53 cores, one Cortex- M4F core, a GC7000Lite GPU and 4kp60, h.265 and VP9 video capability.
  • The i.MX 8M QuadLite, which integrates four ARM Cortex-A53 cores, one Cortex- M4F core and a GC7000Lite GPU.
  • The i.MX 8M Solo, which integrates one ARM Cortex-A53 core, one Cortex-M4F core and a GC7000nanoULTRA GPU.

The i.MX 8 applications processor is highly scalable with a pin- and power-compatible package and comprehensive software support. The i.MX 8 multi-sensory enablement kit (MEK) is now available to prototype i.MX 8M systems. Limited sampling of i.MX 8M will begin in the second quarter of 2017, and general availability is expected in the fourth quarter of 2017.

Source: NXP Semiconductors

700-V CoolMOS P7 Family for Flyback-Based, Low-Power SMPS Applications

Infineon Technologies recently launched the 700-V CoolMOS P7 family for quasi-resonant flyback topologies. Offering performance advantages over superjunction technologies, the MOSFETs are well suited for mobile device chargers and notebook adapters. They also support fast switching and high power density designs for TV adapters, lighting, and moreInfineon CoolMOS_P7

Features and benefits include:

  • Finely graduated RDS(on) x Eoss; lower Qg, Eon and Eoff
  • High switching frequency capable
  • Integrated Zener diode
  • Large variety of packages
  • Low losses
  • Additional 50 V of blocking voltage compared to C6 technology
  • Meets EMI requirements
  • High ESB ruggedness
  • Lower case temperatures

The 700 V CoolMOS P7 family is available with the most relevant RDS(on) package combinations including 360 mΩ up to 1400 mΩ in IPAK SL, DPAK, and TO-220FP.

Source: Infineon Technologies

The Future of Test-First Embedded Software

The term “test-first” software development comes from the original days of extreme programming (XP). In Kent Beck’s 1999 book, Extreme Programming Explained: Embrace Change (Addison-Wesley), his direction is to create an automated test before making any changes to the code.

Nowadays, test-first development usually means test-driven development (TDD): a well-defined, continuous feedback cycle of code, test, and refactor. You write a test, write some code to make it pass, make improvements, and then repeat. Automation is key though, so you can run the tests easily at any time.

TDD is well regarded as a useful software development technique. The proponents of TDD (including myself) like the way in which the code incrementally evolves from the interface as well as the comprehensive test suite that is created. The test suite is the safety net that allows the code to be refactored freely, without worry of breaking anything. It’s a powerful tool in the battle against code rot.

To date, TDD has had greater adoption in web and application development than with embedded software. Recent advances in unit test tools however are set to make TDD more accessible for embedded development.

In 2011 James Grenning published his book, Test Driven Development for Embedded C (Pragmatic Bookshelf). Six years later, this is still the authoritative reference for embedded test-first development and the entry point to TDD for many embedded software developers. It explains how TDD works in detail for an unfamiliar audience and addresses many of the traditional concerns, like how will this work with custom hardware. Today, the book is still completely relevant, but when it was published, the state-of-the art tools were simple unit test and mocking frameworks. These frameworks require a lot of boilerplate code to run tests, and any mock objects need to be created manually.

In the rest of the software world though, unit test tools are significantly more mature. In most other languages used for web and application development, it’s easy to create and run many unit tests, as well as to create mock objects automatically.
Since 2011, the current state of TDD tools has advanced considerably with the development of the open-source tool Ceedling. It automates running of unit tests and generation of mock objects in C applications, making it a lot easier to do TDD. Today, if you want to test-drive embedded software in C, you don’t need to roll-your-own test build system or mocks.

With better tools making unit testing easier, I suspect that in the future test-first development will be more widely adopted by embedded software developers. While previously relegated to the few early adopters willing to put in the effort, with tools lowering the barrier to entry it will be easier for everyone to do TDD.
Besides the tools to make TDD easier, another driving force behind greater adoption of test-first practices will be the simple need to produce better-quality embedded software. As embedded software continues its infiltration into all kinds of devices that run our lives, we’ll need to be able to deliver software that is more reliable and more secure.

Currently, unit tests for embedded software are most popular in regulated industries—like medical or aviation—where the regulators essentially force you to have unit tests. This is one part of a strategy to prevent you from hurting or killing people with your code. The rest of the “unregulated” embedded software world should take note of this approach.

With the rise of the Internet of things (IoT), our society is increasingly dependent on embedded devices connected to the Internet. In the future, the reliability and security of the software that runs these devices is only going to become more critical. There may not be a compelling business case for it now, but customers—and perhaps new regulators—are going to increasingly demand it. Test-first software can be one strategy to help us deal with this challenge.

This article appears in Circuit Cellar 318.

Matt Chernosky wants to help you build better embedded software—test-first with TDD. With years of experience in the automotive, industrial, and medical device fields, he’s excited about improving embedded software development. Learn more from Matt about getting started with embedded TDD at electronvector.com.

New Radiation-Hardened MOSFETs for Space Applications

IR HiRel (an Infineon Technologies company) recently launched its first radiation-hardened MOSFETs based on the proprietary N-channel R9 technology platform. Offering size, weight, and power improvements over previous technologies, the 100-V, 35-A MOSFETs are ideally suited to mission-critical applications requiring an operating life up to and beyond 15 years. Target applications include space-grade DC-DC converters, intermediate bus converters, motor controllers, and high-speed switching designs.Infineon - RAD-hard-MOSFET

The IRHNJ9A7130’s and IRHNJ9A3130’s features, benefits, and specs:

  • Characterized for total ionizing dose (TID) immunity to radiation of 100 krads and 300 krads, respectively.
  • An R DS(on) of 25 mΩ (typical) is 33% lower than the previous device generation.
  • Provide increased power density and reduced power losses in switching applications
  • Improved Single Event Effect (SEE) immunity and have been characterized for useful performance with Linear Energy Transfer (LET) up to 90 MeV/(mg/cm²); at least 10 percent higher than previous generations.
  • Both of the new devices are packaged in a hermetically sealed, lightweight, surface-mount ceramic package (SMD-0.5) measuring just 10.28 mm × 7.64 mm × 3.12 mm.
  • Available in bare die form.

Source: Infineon Technologies