Secure Wi-Fi MCU Provides IoT Connectivity Solution

Espressif Systems has announced the release of the ESP32-S2 Secure Wi-Fi MCU, a highly integrated, low-power, 2.4 GHz Wi-Fi SoC supporting Wi-Fi HT40 and 43 GPIOs. Based on the Xtensa single-core 32-bit LX7 processor, ESP32-S2 can be clocked at up to 240 MHz.

With state-of-the-art power management and RF performance, IO capabilities and security features, ESP32-S2 is well suited for a wide variety of IoT or connectivity-based applications, including smart home and wearables. With an integrated 240 MHz Xtensa core, ESP32-S2 is sufficient for building the most demanding connected devices without requiring external MCUs.

Features:

  • CPU and Memory
    • Xtensa single-core 32-bit LX7 microcontroller
    • 7-stage pipeline
    • Clock frequency of up to 240 MHz
    • Ultra-low-power co-processor
    • 320 kB SRAM, 128 kB ROM, 16 KB RTC memory
    • External SPIRAM (128 MB total) support
    • Up to 1 GB of external flash support
    • Separate instruction and data cache
  • Connectivity
    • Wi-Fi 802.11 b/g/n
    • 1×1 transmit and receive
    • HT40 support with data rate up to 150 Mbps
    • Support for TCP/IP networking, ESP-MESH networking, TLS 1.0, 1.1 and 1.2 and other networking protocols over Wi-Fi
    • Support Time-of-Flight (TOF) measurements with normal Wi-Fi packets
  • IO Peripherals
    • 43 programmable GPIOs
    • 14 capacitive touch sensing IOs
    • Standard peripherals including SPI, I2C, I2S, UART, ADC/DAC and PWM
    • LCD (8-bit parallel RGB/8080/6800) interface and also support for 16/24-bit parallel
    • Camera interface supports 8 or 16-bit DVP image sensor, with clock frequency of up to 40 MHz
    • Full speed USB OTG support
  • Security
    • RSA-3072-based trusted application boot
    • AES256-XTS-based flash encryption to protect sensitive data at rest
    • 4096-bit eFUSE memory with 2048 bits available for application
    • Digital signature peripheral for secure storage of private keys and generation of RSA signatures
  • Power Consumption
    • ESP32-S2 supports fine resolution power control through a selection of clock frequency, duty cycle, Wi-Fi operating modes and individual power control of its internal components.
    • When Wi-Fi is enabled, the chip automatically powers on or off the RF transceiver only when needed, thereby reducing the overall power consumption of the system.
    • ULP co-processor with less than 5 uA idle mode and 24 uA at 1% duty-cycle current consumption. Improved Wi-Fi-connected and MCU-idle-mode power consumption.
  • Software
    • ESP32-S2 supports Espressif’s software development framework (ESP-IDF), which is a mature and production-ready platform, already used by millions of devices deployed in the field. Availability of common cloud connectivity agents and common product features shortens the time to market.

Engineering samples of ESP32-S2 beta are available this month (June).

Espressif Systems | www.espressif.com

Dual-Core MCUs Blend High Performance and Enhanced Security

STMicroelectronics has announced new STM32H7 MCUs which it claims are the industry’s highest-performing Arm Cortex-M general-purpose MCUs, combining dual-core performance with power-saving features and enhanced cyber protection. The new devices leverage a 480 MHz version of the Cortex-M7, the highest performing member of Arm’s Cortex-M family, and add a 240 MHz Cortex-M4 core.

With ST’s smart architecture, efficient L1 cache, and adaptive real-time ART Accelerator, the MCUs set new speed records at 1327 DMIPS and 3224 CoreMark executing from embedded flash. ST’s Chrom-ART Accelerator provides a boost to graphics performance. To maximize energy efficiency, each core operates in its own power domain and can be turned off individually when not needed.
Developers can easily upgrade existing applications through flexible use of the two cores. They can add a sophisticated user interface to an application such as a motor drive formerly hosted on a single-core Cortex-M4 MCU by migrating legacy code to the STM32H7 Cortex-M4 with the new GUI running on the Cortex-M7. Another example is to boost application performance by offloading intensive workloads such as neural networks, checksums, DSP filtering or audio codecs.

The dual-core architecture also helps simplify code development and accelerate time to market in projects where user-interface code may be developed separately from real-time control or communication features.

STM32H7 MCUs come with pre-installed keys and native secure services including Secure Firmware Install (SFI). SFI lets customers order standard products anywhere in the world and have the encrypted firmware delivered to an external programming company without exposing unencrypted code. In addition, built-in support for Secure Boot and Secure Firmware Update (SB-SFU) protects Over the Air (OTA) feature upgrades and patches.

Compared to flash-less processors, STM32H7 MCUs deliver high performance with the extra advantage of up to 2 MB Flash and 1 MB SRAM on-chip, says ST. This helps to better handle space constraints and simplify the design of smart objects in industrial, consumer and medical applications with real-time performance or AI-processing requirements. Moreover, the Cortex-M7 level 1 cache and parallel and serial memory interfaces offer unlimited and fast access to external memory.

Additional advanced features include Error Code Correction (ECC) for all flash and RAM memory to increase safety, multiple advanced 16-bit ADCs, external ambient-temperature range up to 125°C allowing use in severe environments, an Ethernet controller and multiple FD-CAN controllers giving communication-gateway capabilities, and ST’s latest high-resolution timer for generating precision waveforms.

ST has already extended the STM32Cube ecosystem by adding STM32CubeH7 firmware modules with application source code, including graphical solutions based on TouchGFX and STemWin graphical-stack library. There are also new Evaluation, Discovery and Nucleo boards. Developers can leverage all the standard elements of the STM32Cube development environment, including the ST-MC-SUITE motor-control toolkit, STM32Cube.AI machine-learning toolkit, STM32CubeMX, STM32CubeProgrammer and certified partner solutions for STM32.

STM32H7 dual-core MCUs are entering production and samples are available now. A broad selection of packages is offered, including WLCSP. Budgetary pricing starts at $8.19 for orders of 10,000 pieces The STM32H7 single-core MCUs including the Value line are also available at a budgetary pricing starting from $3.39 for orders of 10,000 pieces.

STMicroelectronics | www.st.com

 

EOG-Controlled Video Game

Eyes as Interface

There’s much be to learned about how electronics can interact with biological signals—not only to record, but also to see how they can be used as inputs for control applications. With ongoing research in fields such as virtual reality and prosthetics, new systems are being developed to interpret different types of signals for practical applications. Learn how these three Cornell graduates use electrooculography (EOG) to control a simple video game by measuring eye movements.

By Eric Cole, Evan Mok and Alex Huang

The human eye naturally acts as a dipole, in which the retina at the back of the eye is negatively charged, and the cornea at the front of the eye is positively charged. EOG is a recording technique that measures this potential difference, and can be used to

Figure 1
Electrode placement for recording. An Ag-AgCl (silver-silver chloride) electrode was placed at each of the labeled points. Points A and B record the EOG signal for the right and left eyes, and point C provides a ground reference.

quantify eye movement [1]. A typical electrode placement pattern for EOG is shown in Figure 1. Each of the electrodes A and B records a voltage related to eye movement, and an electrode at point C serves as a ground reference.

When a user looks left, the cornea is close to electrode B and it records a positive voltage, while the retina is closer to electrode A, yielding a negative voltage. Similarly, looking right produces a negative voltage at B and a positive voltage at A. The difference between VB and VA relative to ground at C changes monotonically with gaze direction, and can be reliably used to model horizontal eye movement.

System Overview

The system we designed uses eye movements to play a video game on a display screen. Electrodes are placed on a player’s head to record only the horizontal EOG signal as shown in Figure 2. This signal is then filtered and amplified via an analog circuit and sent to an ADC on a Microchip Technology PIC32 microcontroller (MCU) (Figure 3). The PIC32 MCU stores the reading as a digital value and uses it to control a cursor on an LCD display screen. A program on the PIC32 continually displays obstacles that move across the screen, and the player moves his or her eyes to control the cursor and avoid obstacles.

Figure 2
Characterization of EOG signal. An example signal output is shown for a gain of approximately 885.

Figure 3
System overview. “Eye recording” is accomplished with the raw electrode signal.

This system is entirely powered without connection to an AC power source, instead using a 9 V battery to provide power for amplification and a chargeable power source to power the PIC32. This choice of a power source was important, because it enforces necessary safety considerations for biomedical recording. Connecting a high voltage source to a human user and accidentally completing a circuit path to AC ground could result in serious injury, so great care was taken to use battery power for this project.

A secondary oscilloscope program was also necessarily designed to satisfy a key safety need: The ability to view the recorded EOG signal and test the recording hardware while the circuit is isolated. A normal oscilloscope cannot be used for this purpose for the reasons stated earlier. Care was also taken to apply and fasten the electrodes properly before every session.

Recording and Application

Three Ag-AgCl (silver-silver chloride) electrodes are placed around the eyes using a skin-safe adhesive gel—one beside each eye, and one on the forehead as a ground reference—at points A, B, and C respectively, in Figure 1. These electrodes provide the gateway between the biological signal and the digital world, detecting the voltage generated by ions at the skin surface and transducing it into an equivalent electron-based signal.

This voltage is generated directly at the eye, and has some attenuation through the skin surface. A typical magnitude of the raw EOG signal is several millivolts. The voltage readings from the two eye electrodes are sent to a Texas Instruments (TI) INA121 differential amplifier, which amplifies the difference between the two input signals. This yields a negative or positive voltage based on direction of eye movement. The INA121 provides low noise, a high common-mode rejection ratio, and is suitable for the high-input impedance requirement associated with recording biological signals. Figure 4 shows the full schematic of the implementation.

A second amplification stage using a TI LM358-based balanced subtractor configuration provides further amplification. This stage reduces the DC voltage component output from the differential amplifier, while further amplifying the difference to a range of 0 to 3.3 V—the scale allowed by the PIC32 MCU’s on-chip ADC. The resulting signal is a voltage centered at approximately 1.6 V when the user looks straight, with about a 1 V increase or decrease when the user looks left or right, respectively. …

Read the full article in the July 348 issue of Circuit Cellar
(Full article word count: 3023 words; Figure count: 6 Figures.)

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July Circuit Cellar: Sneak Preview

The July issue of Circuit Cellar magazine is out next week! This 84-page publication will make a satisfying thud sound when it lands on your desk and it’s crammed full of excellent embedded electronics articles prepared for you.

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CONNECTED SYSTEMS IN ACTION

Embedded Computing
in Railway Systems
Railway systems keep getting more advanced. On both the control side and passenger entertainment side, embedded computers and power supplies play critical roles. Railway systems need sophisticated networking, data collection and real-time control, all while meeting safety standards. Circuit Cellar Chief Editor Jeff Child looks at the latest technology trends and products relevant to railway applications.

Product Focus:
IoT Interface Modules
The fast growing IoT phenomenon is driving demand for highly integrated modules designed for the IoT edge. Feeding those needs, a new crop of IoT modules have emerged that offer pre-certified solutions that are ready to use. This Product Focus section updates readers on this technology trend and provides a product album of representative IoT modules.

TECHNOLOGIES AND TECHNIQUES FOR ENGINEERS

FPGA Signal Processing
Offering the dual benefits of powerful signal processing and system-level integration, FPGAs have become a key technology for embedded system developers. Makers of chip and board-level FPGA products are providing complete solutions to enable developers to meet their application needs. Circuit Cellar Chief Editor Jeff Child explores the latest technology trends and product developments in FPGA signal processing.

Macros for AVR Assembler Programming
The AVR microcontroller instruction set provides a simplicity that makes it good for learning the root principles of machine programming. There’s also a rich set of macros available for the AVR that ease assembler-level programming. In this article, Wolfgang Matthes steps you through these principles, with the goal of helping programmers “think low-level, write high-level” when they approach embedded systems software development.

Inrush Current Limiters in Action
At the moment a high-power system is switched on, high loads can result in serious damage—even when the extra load is only for short time. Inrush current limiters (ICLs) can help prevent these issues. In this article, TDK Electronics’ Matt Reynolds examines ICLs based on NTC and PTC thermistors, discussing the underlying technology and the device options.

A Look at Cores with TrustZone-M
It’s not so easy to keep up with all the new security features on the latest and greatest embedded processors—especially while you’re busy focusing on the more fundamental and unique aspects of your design. In this article, Colin O’Flynn helps out by examining the new processor cores using TrustZone-M, a feature that helps you secure even low-cost and lower power system designs.

PROJECTS THAT REUSE & RECYCLE

Energy Monitoring Part 2
In Part 1 of this article series, George Novacek began describing an MCU-based system he built to monitor his household energy. Here, he continues that discussion, this time focusing on the electrical power tracking module. As the story shows, he stuck to a design challenge of building the system with as many components he already had in his component bins.

Variable Frequency Drive Part 1
Modern appliances claim to be more efficient, but they’re certainly not designed to last as long as older models. In this project article, Brian Millier describes how he reused subsystems from a defunct modern washing machine to power his bandsaw. The effort provides valuable insights on how to make use of the complete 3-phase Variable Frequency Drive (VFD) borrowed from the washing machine.

FUN PROJECT ARTICLES WITH ALL THE DETAILS

Windless Wind Chimes (Part 2)
In part 1 of this article series, Jeff Bachiochi built a system to simulate breezes randomly playing the sounds of suspended wind chimes. In part 2 the effort evolves into a less random, more orchestrated project. Jeff decided this time to craft a string of chromatically tuned chimes, similar to what an orchestra might use so the project could be used to play music. The project relies on MIDI, an industry standard music technology protocol designed to create and share music and artistic works.

Building a Smart Frying Pan
There’s almost no limit to what an MCU can be used for—-including objects that previously had no electronics at all. In this article, learn how Cornell University graduate Joseph Dwyer build a Microchip PIC32 MCU-based system that wirelessly measures and controls the temperature of a pan on a stove. The system improves both the safety and reliability of cooking on the stove, and has potentially interesting commercial applications.

EOG-Controlled Video Game
There’s much be to learned about how electronics can interact with biological signals—not only to record, but also to see how they can be used as inputs for control applications. With ongoing research in fields such as virtual reality and prosthetics, new systems are being developed to interpret different types of signals for practical applications. Learn how Cornell graduates  Eric Cole, Evan Mok and Alex Huang use electrooculography (EOG) to control a simple video game by measuring eye movement.

Infineon Technologies to Acquire Cypress Semiconductor

Infineon Technologies and Cypress Semiconductor have announced that the companies have signed a definitive agreement under which Infineon will acquire Cypress for US $23.85 per share in cash, corresponding to an enterprise value of €9.0 billion.

With the addition of Cypress, Infineon expects to strengthen its focus on structural growth drivers and serve a broader range of applications. This will accelerate the company’s path of profitable growth of recent years. Cypress has a differentiated portfolio of microcontrollers as well as software and connectivity components that are highly complementary to Infineon’s leading power semiconductors, sensors and security solutions.

According to their joint press release, combining these technology assets will enable comprehensive advanced solutions for high-growth applications such as electric drives, battery-powered devices and power supplies. The combination of Infineon’s security expertise and Cypress’s connectivity know-how will accelerate entry into new IoT applications in the industrial and consumer segments. In automotive semiconductors, the expanded portfolio of microcontrollers and NOR flash memories will offer great potential, especially in light of their growing importance for advanced driver assistance systems and new electronic architectures in vehicles.

Under the terms of the agreement, Infineon will offer US$23.85 in cash for all outstanding shares of Cypress. This corresponds to a fully diluted enterprise value for Cypress of €9.0 billion. The offer price represents a 46 percent premium to Cypress’s unaffected 30-day volume-weighted average price during the period from 15 April to 28 May 2019, the last trading day prior to media reports regarding a potential sale of Cypress.

Cypress expects to continue its quarterly cash dividend payments until the transaction closes. This includes Cypress’s previously announced quarterly cash dividend of US$0.11 per share, payable on July 18, 2019 to holders of record of Cypress’s common stock at the close of business on June 27, 2019.

The funding of the acquisition is fully underwritten by a consortium of banks. Infineon is committed to retaining a solid investment grade rating and, consequently, Infineon intends to ultimately finance approximately 30 percent of the total transaction value with equity and the remainder with debt as well as cash on hand. The financial policy to preserve a strategic cash reserve remains in place.

The acquisition is subject to approval by Cypress’s shareholders and the relevant regulatory bodies as well as other customary conditions. The closing is expected by the end of calendar year 2019 or early 2020.

Cypress Semiconductor | www.cypress.com
Infineon Technologies | www.infineon.com

MCUs with EtherCAT Target Industrial Applications

Renesas Electronics has introduced the RX72M Group of RX MCUs featuring an EtherCAT slave controller for industrial Ethernet communication. The new product group offers a high-performance, single-chip MCU solution with large memory capacities for industrial equipment requiring control and communication functions such as compact industrial robots, programmable logic controllers, remote I/O and industrial gateways.
According to Renesas, the use of EtherCAT in industrial Ethernet is growing fast, and is currently used on dedicated MCUs, ICs, and high-end SoC devices specialized for EtherCAT communication. The new RX72M Group achieves the superior performance of a 1396 CoreMark score at 240 MHz as measured by EEMBC Benchmarks, and it is capable of both application processing and EtherCAT communication. Combining a motor-control MCU with on-chip EtherCAT slave functions allows industrial application developers reduce their bill of materials (BOM) and support the miniaturization levels required for industrial equipment design.

The RX72M Group is the first RX MCU group to include an EtherCAT slave controller featuring the RX family’s highest SRAM capacity—1 MB of SRAM—and 4 MB of Flash memory. The large-capacity SRAM allows the MCUs to run multiple memory-intensive middleware systems, such as TCP/IP, web servers, and file systems, at high speed without the use of external memory. It also provides flexibility for the support of future functional expansions, such as OPC United Architecture (OPC UA) with no additional memory required. The on-board flash memory operates as two 2 MB banks, which enables stable operation of the end equipment, such as executing a program in one flash memory while simultaneously conducting background rewrites in the other flash memory.

Key features of the RX72M MCUs:

  • The first EtherCAT slave controller for industrial Ethernet communication in an RX MCU
  • High performance with a CoreMark benchmark score of 1396 at up to 240 MHz, and the first embedded double precision floating point unit (FPU) in an RX MCU
  • High-speed flash memory system supporting readout up to 120 MHz, creating high-performance and low-variability execution environment
  • Dedicated trigonometric function (sin, cos, arctan and hypot fucntions) accelerators and register bank save function supporting high-precision motor control implementation – a feature shared with the Renesas RX72T motor-control MCUs
  • Reliable cryptography functions such as encryption module and memory protection function in hardware to protect encryption keys – this prevents application systems from being copied without authorization and supports authentication for genuine equipment
  • Flexible package options including 176-pin LQFP and 176-pin BGA configurations as well as the first 224-pin BGA package for RX MCUs, which offers additional space saving for size-constrained designs

Samples of the RX72M Group of MCUs are available now. Renesas will begin mass production orders starting September 2019.

Renesas Electronics | www.renesas.com

 

 

June Circuit Cellar: Sneak Preview

The June issue of Circuit Cellar magazine is out next week!. We’ve been tending our technology crops to bring you a rich harvest of in-depth embedded electronics articles. We’ll have this 84-page magazine brought to your table very soon..

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TOOLS AND CONCEPTS FOR ENGINEERS

Integrated PCB Design Tools
After decades of evolving their PCB design tool software packages, the leading tool vendors have the basics of PCB design nailed down. In recent years, these companies have continued to come up with new enhancements to their tool suites, addressing a myriad of issues related to not just the PCB design itself, but the whole process surrounding it. Circuit Cellar Chief Editor Jeff Child looks at the latest integrated PCB design tool solutions.

dB for Dummies: Decibels Demystified
Understanding decibels—or dB for short—may seem intimidating. Frequent readers of this column know that Robert uses dB terms quite often—particularly when talking about wireless systems or filters. In this article, Robert Lacoste discusses the math underlying decibels using basic concepts. The article also covers how they are used to express values in electronics and even includes a quiz to help you hone your decibel expertise.

Understanding PID
As a means for implementing feedback control systems, PID is an important concept in electronics engineering. In this article, Stuart Ball explains how PID can be applied and explains the concept by focusing on a simple circuit design.

DESIGNING CONNECTED SYSTEMS

Sensor Connectivity Trends
While sensors have always played a key role in embedded systems, the exploding Internet of Things (IoT) phenomenon has pushed sensor technology to the forefront. Any IoT implementation depends on an array of sensors that relay input back to the cloud. Circuit Cellar Chief Editor Jeff Child dives into the latest technology trends and product developments in sensors with an emphasis on their connectivity aspects.

Bluetooth Mesh (Part 3)
In this next part of his article series on Bluetooth mesh, Bob Japenga looks at how to create secure provisioning for a Bluetooth Mesh network without requiring user intervention. He takes a special look at an attack which Bluetooth’s asymmetric key encryption is vulnerable to called Man-in-the-Middle.

PONDERING POWER AND ENERGY

Product Focus: AC-DC Converters
To their peril, embedded system developers often treat their choice of power supply as an afterthought. But choosing the right AC-DC converter is critical to the ensuring your system delivers power efficiently to all parts of your system. This Product Focus section updates readers on these trends and provides a product album of representative AC-DC converter products.

Energy Monitoring (Part 1)
The efficient use of energy is a topic moving ever more front and center these days as climate change and energy costs begin to affect our daily lives. Curious to discover how efficient his own energy consumption was, George Novacek built an MCU-based system to monitor his household energy. And, in order to make sure this new device wasn’t adding more energy use, he chose to make the energy monitoring system solar-powered.

Building a PoE Power Subsystem
Power-over-Ethernet (PoE) allows a single cable to provide both data interconnection and power to devices. In this article, Maxim Integrated’s  and Maxim Integrated’s Thong Huynh and Suhei Dhanani explore the key issues involved in implementing rugged PoE systems. Topics covered include standards compliance, interface controller selection, DC-DC converter choices and more.

Taming Your Wind Turbine
While you can buy off-the-shelf wind power generators these days, they tend to get bad reviews from users. The problem is that harnessing wind energy takes some “taming” of the downstream electronics. In this article, Alexander Pozhitkov discusses his characterization project for a small wind turbine. This provides a guide for designing your own wind energy harvesting system.

MORE PROJECT ARTICLES WITH ALL THE DETAILS

Windless Wind Chimes (Part 1)
Wind chimes make a pleasant sound during the warm months when windows are open. But wouldn’t it be nice to simulate those sounds during the winter months when your windows are shut? In part 1 of this project article, Jeff Bachiochi builds a device that simulates a breeze randomly playing suspended wind chimes. Limited to the standard 5-note pentatonic chimes, this device is based on a Microchip PIC18 low power microcontroller.

GPS Guides Robotic Car
In this project article, Raul Alvarez-Torrico builds a robotic car that navigates to a series of GPS waypoints. Using the Arduino UNO for a controller, the design is aimed at robotics beginners that want to step things up a notch. In the article, Raul discusses the math, programing and electronics hardware choices that went into this project design.

Haptic Feedback Electronic Travel Aid
Time-of-flight sensors have become small and affordable in the last couple years. In this article, learn how Cornell graduates Aaheli Chattopadhyay, Naomi Hess and Jun Ko detail creating a travel aid for the visually impaired with a few time-of-flight sensors, coin vibration motors, an Arduino Pro Mini, a Microchip PIC32 MCU, a flashlight and a sock.

Capacitive vs. Inductive Sensing

Touch Trade-Offs

Touch sensing has become an indispensable technology across a wide range of embedded systems. In this article, Nishant discusses capacitive sensing and inductive sensing, each in the context of their use in embedded applications. He then explores the trade-offs between the two technologies, and why inductive sensing is preferred over capacitive sensing in some use cases.

By Nishant Mittal

Touch sensing was first implemented using resistive sensing technology. But resistive sensing had a number of disadvantages, including low sensitivity, false triggering and shorter operating life. All of that discouraged its use and led to its eventual downfall in the market.

Today whenever people talk about touch sensing, they’re usually referring to capacitive sensing. Capacitive sensing has proven to be robust not only in a normal environmental use cases but also underwater, thanks to its water-resistant capabilities. As with any technology, capacitive sensing comes with a new set of disadvantages. These disadvantages tend to more application-specific. That situation opened the door for the advent of inductive sensing technology.

In this article, we’ll discuss capacitive sensing for embedded applications and how it can be used in various applications. We will then explore the use of inductive sensing in embedded products and why inductive sensing is preferred over capacitive sensing in some use cases. Finally, we’ll compare the advantages of inductive sensing over capacitive sensing in these applications.

Capacitive Sensing for Embedded

Capacitive sensing operates on the principle of monitoring the change in parasitic capacitance due to a finger touch (Figure 1). Capacitive sensing has been used primarily in two different forms: self-capacitance and mutual-capacitance. In self-capacitance mode, the net capacitance due to a finger touch and board capacitance is additive. This capacitance includes PCB traces and PCB materials like FR4, which has more capacitance compared to Flex materials and many similar dielectrics. Self-capacitance mode is useful in general touch application like buttons for touch-and-respond applications. In contrast, mutual capacitance is well-suited for applications involving more complex sensing such as gestures, multi-touch and sliders.

FIGURE 1
Capacitive sensing technique

Mutual capacitance sensing uses two different lines: TX(Transmitter) and RX(Receiver). The Transmitter sends a PWM signal with respect to the system VDD and GND. The Receiver detects the amount of charge received on the RX electrode.

One of the difficult use cases of capacitive sensing is that it cannot operate perfectly underwater. It also requires relatively strict design guidelines to be followed for error-free operation. Capacitive sensing performance is also impacted by nearby LEDs and power lines on PCBs. Implementing auto-tuning with variation in trace capacitance, variation in capacitive sensing buttons and different slider sizes and shapes all require different designs. Implementation challenges in industrial applications include using capacitive sensing with thicker glass material (display glass) and meeting capacitive sensor sensitivity requirements with those types of materials.

Inductive Sensing for Embedded

Inductive sensing enables the next-generation of touch technology in applications involving metal-over-touch use cases such as in automotive, industrial and many embedded and IoT applications. Inductive sensing is based on the principle of electromagnetic coupling, between a coil and the target (Figure 2). When a metal target comes closer to the coil, its magnetic field is obstructed and it passes through the metal target before coupling to its origin. This phenomenon causes some energy to get transferred to the metal target—referred to as eddy current—that causes a circular magnetic field. Eddy current induces a reverse magnetic field, in turn leading to a reduction in inductance.

FIGURE 2
Inductive sensing technique [1]

To cause the resonant frequency to occur, a capacitor is added in parallel to the coil to cause the LC tank circuit. As the inductance starts reducing, the frequency shifts upward changing the amplitude throughout. In contrast to a capacitive sensor, inductive sensing is able to operate reliably in the presence of water thanks to the removal of a dielectric from the sensor. This advantage brings inductive sensing touch sensing to a wide range of applications that involve liquids such as underwater equipment, flow meters, RPM detection, medical instruments and many others. Inductive sensing also supports biomedical applications. In general applications, inductive sensing enables replacement of mechanical switches and proximity sensing of metal objects. For example, in automotive applications, inductive sensing can be used to replace mechanical handles as well as detect car proximity. Some of these examples will be discussed in detail later..

Read the full article in the May 346 issue of Circuit Cellar
(Full article word count: 1842 words; Figure count: 6 Figures.)

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Note: We’ve made the October 2017 issue of Circuit Cellar available as a free sample issue. In it, you’ll find a rich variety of the kinds of articles and information that exemplify a typical issue of the current magazine.

5 V MCU Family Provides Water Tolerant Touch Integration

NXP Semiconductor has announced its 5 V KE1xZ family of MCUs. Based on the Arm Cortex-M0+ core, the MCUs are suited for embedded control systems in harsh electrical environments and provide an integrated CAN controller and capacitive touch from 32 KB flash. Designed for a wide range of industrial applications, the KE1xZ family offers mixed-signal integration across a range of compact memory variants. The 1-MS/s ADC and FlexTimer modules, combined with NXP’s Freemaster software tools library and Motor Control Application Tuning plugin (MCAT) enable designs of Brushless DC (BLDC) and other motor-control systems.

NXP’s KE1xZ MCU family offers advanced noise immunity, water-tolerant touch and low-power wake-on-touch operation—essential features for the strict electromagnetic compatibility (EMC) standards of the industrial and home appliance markets. NXP’s touch IP, combined with software and tools provide a high level of stability, accuracy and ease of use, with continued responsiveness and functionality through wet conditions. It can sustain 10 V in conducted noise, in alignment with International Electrotechnical Commission (IEC) 6100-4-6 test level 3.

Additional KE1xZ MCU features:

  • Internal 48MHz internal reference clock with 1% accuracy over full operating range
  • Boot ROM with built in bootloader and 128-bit unique device identifier (UID)
  • ADC self-calibration feature
  • Flash Access Control (FAC)
  • Cyclic Redundancy Check (CRC) generator module
  • Internal watchdog (WDOG) with independent clock source and external watchdog monitor (EWM)
  • On-chip clock loss monitoring
  • IEC 60730 Class B safety certification
  • LQFP package with 48- and 44-pin options

The KE1xZ MCU family will be available globally in March 2019 from NXP and its distribution partners with a suggested resale price from $0.79 at 10,000-unit quantities. NXP enables developers through its MCUXpresso software and tools ecosystem, along with its FRDM-KE15Z and FRDM-TOUCH development platforms (see image above), with respective suggested resale prices of $35 and $15. Third-party support is enabled from the broad ARM ecosystem.

NXP Semiconductor | www.nxp.com

 

May Circuit Cellar: Sneak Preview

The May issue of Circuit Cellar magazine is out next week!. We’ve been hard at work laying the foundation and nailing the beams together with a sturdy selection of  embedded electronics articles just for you. We’ll soon be inviting you inside this 84-page magazine.

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Here’s a sneak preview of May 2019 Circuit Cellar:

EMBEDDED COMPUTING AT WORK

Technologies for Digital Signage
Digital signage ranks among the most dynamic areas of today’s embedded computing space. Makers of digital signage players, board-level products and other technologies continue to roll out new solutions for implementing powerful digital signage systems. Circuit Cellar Chief Editor Jeff Child looks at the latest technology trends and product developments in digital signage.

PC/104 and PC/104 Family Boards
PC/104 has come a long way since its inception over 25 ago. With its roots in ISA-bus PC technology, PC/104 evolved through the era of PCI and PCI Express by spinning off its wider family of follow on versions including PC/104-Plus, PCI-104, PCIe/104 and PCI/104-Express. This Product Focus section updates readers on these technology trends and provides a product gallery of representative PC/104 and PC/104-family boards.

TOOLS & TECHNIQUES FOR EMBEDDED ENGINEERING

Code Analysis Tools
Today it’s not uncommon for embedded devices to have millions of lines of software code. Code analysis tools have kept pace with these demands making it easier for embedded developers to analyze, debug and verify complex embedded software. Circuit Cellar Chief Editor Jeff Child explores the latest technology trends and product developments in code analysis tools.

Transistor Basics
In this day and age of highly integrated ICs, what is the relevance of the lone, discrete transistor? It’s true that most embedded systems can be solved by chip level solutions. But electronic component vendors do still make and sell individual transistors because there’s still a market for them. In this article, Stuart Ball reviews some important basics about transistors and how you can use them in your embedded system design.

Pressure Sensors
Over the years, George Novacek has done articles examining numerous types of sensors that measure various physical aspects of our world. But one measurement type he’s not yet discussed in the past is pressure. Here, George looks at pressure sensors in the context of using them in an electronic monitoring or control system. The story looks at the math, physics and technology associated with pressure sensors.

MICROCONTROLLERS DO IT ALL

Robotic Arm Plays Beer Pong
Simulating human body motion is a key concept in robotics development. With that in mind, learn how these Cornell graduates Daniel Fayad, Justin Choi and Harrison Hyundong Chang accurately simulate the movement of a human arm on a small-sized robotic arm. The Microchip PIC32 MCU-based system enables the motion-controlled, 3-DoF robotic arm to take a user’s throwing motion as a reference to its own throw. In this way, they created a robotic arm that can throw a ping pong ball and thus play beer pong.

Fancy Filtering with the Teensy 3.6
Signal filtering entails some tricky tradeoffs. A fast MCU that provides hardware-based floating-point capability eases some of those tradeoffs. In the past, Brian Millier has used the Arm-based Teensy MCU modules to serve meet those needs. In this article, Brian taps the Teensy 3.6 Arm MCU module to perform real-time audio FFT-convolution filtering.

Real-Time Stock Monitoring Using an MCU
With today’s technology, even very simple microcontroller-based devices can fetch and display data from the Internet. Learn how Cornell graduates David Valley and Saelig Khatta built a system using that can track stock prices in real-time and display them conveniently on an LCD screen. For the design, they used an Espressif Systems ESP8266 Wi-Fi module controlled by a Microchip PIC32 MCU. Our fun little device fetches chosen stock prices in real-time and displays them on a screen.

… AND MORE FROM OUR EXPERT COLUMNISTS

Attacking USB Gear with EMFI
Many products use USB, but have you ever considered there may be a critical security vulnerability lurking in your USB stack? In this article, Colin O’Flynn walks you through on example product that could be broken using electromagnetic fault injection (EMFI) to perform this attack without even removing the device enclosure.

An Itty Bitty Education
There’s no doubt that we’re living in a golden age when it comes to easily available and affordable development kits for fun and education. With that in mind, Jeff Bachiochi shares his experiences programming and playing with the Itty Bitty Buggy from Microduino. Using the product, you can build combine LEGO-compatible building blocks into mobile robots controlled via Bluetooth using your cellphone.

Capacitive Touch-Key MCUs Enable 2D/3D Gesture Control

Renesas Electronics has introduced two touch-free user interface (UI) solutions for simplifying the design of 2D and 3D control-based applications. Based on Renesas’ capacitive sensor microcontrollers, the new solutions support the development of UI that allows users to operate home appliances, as well as industrial and OA equipment without touching the devices. The UI solutions make it possible for appliance and equipment manufacturers to quickly develop touch-free interfaces that increase the added-value of their products in terms of both equipment convenience and design.
There are a variety of situations where touch-free operation is advantageous, such as when the users’ hands are wet, when the controls are out of reach, or when it is not safe for the user to touch the controls. Renesas new touch-free UI, for example in the kitchen, users could adjust water temperature and flow rate through hand gestures near the faucets or adjust stove fan operation by holding a hand over the hood. The touch-free UI solutions allow customers to easily implement these interfaces in their embedded equipment. The reference designs are available for download.

The new gesture solutions detect motion in a 2D coordinate system and in 3D space, respectively. With both solutions, Renesas provides design materials (circuit diagrams, board design data files and parts lists) that form the reference hardware for the capacitive touch-key MCU, as well as coordinate calculation middleware, sample programs, application notes and an evaluation tool for monitoring the detected coordinates. The touch-free UI solutions have passed class B testing for the IEC 61000 4-3 level 3 and 4-6 level 3 noise immunity standards, and can achieve stable operation.

The 3D gesture solution is available in three different sizes and can be selected based on the application:

  • Standard version (160 × 160 × 100 mm) with RX231 MCU
  • Miniature version (80 × 80 × 80 mm) with RX130 MCU
  • Slim version (100 × 100 × 20 mm) with RX130 MCU for additional space saving

Renesas Electronics | www.renesas.com

 

Low-Power Wireless MCUs Provide Real-Time Performance

STMicroelectronics (ST) has announced its latest Bluetooth offering, its STM32WBx5 dual-core wireless MCUs. The devices come with Bluetooth 5, OpenThread and ZigBee 3.0 connectivity combined with ultra-low-power performance. Fusing features of ST’s STM32L4 Arm Cortex-M4 MCUs and in-house radio managed by a dedicated Cortex-M0+, the STM32WBx5 is power-conscious yet capable of concurrent wireless-protocol and real-time application execution. It is well suited to remote sensors, wearable trackers, building automation controllers, computer peripherals, drones and other IoT devices.
Security features of the STM32WBx5 MCUs include Customer Key Storage (CKS), Public Key Authorization (PKA), and encryption engines for the radio MAC and upper layers. The MCUs have up to 1 MB of on-chip flash and a Quad-SPI port for efficient connection to external memory, if needed. Additional features include crystal-less Full-Speed USB, 32 MHz RF oscillator with trimming capacitors, a touch-sense controller, LCD controller, analog peripherals and multiple timers and watchdogs. The balun for antenna connection is also integrated.

Leveraging ultra-low-power technologies of the STM32L4 line, STM32WBx5 MCUs feature multiple power-saving modes including 13 nA shutdown mode, adaptive voltage scaling, and the adaptive real-time (ART) accelerator to maximize energy efficiency and ensure long-lasting performance in self-powered applications. The integrated radio transmitter is optimized for high RF performance and low power consumption to maximize battery runtime. The RF output power is programmable up to +6 dBm in 1 dB increments, and the MCU draws only 5.2 mA when transmitting at 0 dB. Receive sensitivity is -96 dBm for BLE communication at 1mbps. Designed for a link budget of 102 dB, the radio ensures robust communication over long connection distances and includes support for an external Power Amplifier (PA).

STMicroelectronics | www.st.com

 

PIC MCU Development Board for Cloud IoT Core

Microchip Technology has announced an IoT rapid development board for Google Cloud IoT Core that combines a low-power PIC MCU, CryptoAuthentication secure element IC and fully certified Wi-Fi network controller. The solution provides a simple way to connect and secure PIC MCU-based applications. It’s designed to remove the added time, cost and security vulnerabilities that come with large software frameworks and RTOS.
As part of Microchip’s extended partnership with Google Cloud, the PIC-IoT WG Development Board enables PIC MCU designers to easily add cloud connectivity to next-generation products using a free online portal at www.PIC-IoT.com. Once connected, developers can use Microchip’s MPLAB Code Configurator (MCC) rapid development tool to develop, debug and customize their application.

The board includes:

  • eXtreme Low-Power (XLP) PICMCU with integrated Core Independent Peripherals: Well suited for battery-operated, real-time sensing and control applications, the PIC24FJ128GA705 MCU provides the simplicity of the PIC architecture with added memory and advanced analog integration. With the latest Core Independent Peripherals (CIPs) designed to handle complex applications with less code and decreased power consumption, the device provides the ideal combination of performance with extremely low power consumption.
  • Secure element to protect the root of trust in hardware: The ATECC608A CryptoAuthentication device provides a trusted and protected identity for each device that can be securely authenticated. ATECC608A devices come pre-registered on Google Cloud IoT Core and are ready for use with zero-touch provisioning.
  • Wi-Fi connectivity to Google Cloud: The ATWINC1510 is an industrial-grade, fully certified IEEE 802.11 b/g/n IoT network controller that provides an easy connection to an MCU of choice via a flexible SPI interface. The module relieves designers from needing expertise in networking protocols.

Google Cloud IoT Core provides a fully managed service that enables designers to easily and securely connect, manage and ingest data from devices at a global scale. The platform collects, processes and analyzes data in real time to enable designers to improve operational efficiency in embedded designs.

The PIC-IoT WG development board is supported by the MPLAB X Integrated Development Environment (IDE) and MCC rapid prototyping tool. The board is compatible with more than 450 MikroElektronika Click boards that expand sensors and actuator options. Developers who purchase the kit will have access to an online portal for immediate visualization of their sensors’ data being published. Supported by complete board schematics and demo code, the PIC-IoT WG development board helps get customers to market quickly with differentiated IoT end products.

The PIC-IoT WG Development Board (AC164164) is available in volume production now for $29 each.

Microchip Technology | www.microchip.com

Low-Power Bluetooth MCUs Deliver Mesh Networking

Cypress Semiconductor has announced it is sampling two low-power, dual-mode Bluetooth 5.0 and Bluetooth Low Energy (BLE) MCUs that include support for Bluetooth mesh networking for the Internet of Things (IoT). The new CYW20819 and CYW20820 MCUs each provide simultaneous Bluetooth 5.0 audio and BLE connections.

The CYW20819 Bluetooth/BLE MCU has the ability to maintain Serial Port Profile (SPP) protocol connections and Bluetooth mesh connections simultaneously. The CYW20820 offers the same features and integrates a power amplifier (PA) with up to 10 dBm output power for long-range applications up to 400 m and whole-home coverage. This provides classic Bluetooth tablet and smartphone connections while enabling a low-power, standards-compliant mesh network for sensor-based smart home or enterprise applications.

Both MCUs embed the Arm Cortex-M4 core. It enables operation at 60% lower active power for connected 200-ms beacons compared to current solutions—delivering up to 123 days of battery life from a CR2032 coin cell battery. Previously, users needed to be in the immediate vicinity of a Bluetooth device to control it without an added hub. Using Bluetooth mesh networking technology, combined with the high-performance integrated PA in the CYW20820, the devices within a network can communicate with each other.

Cypress Semiconductor | www.cypress.com

MCU-Based Solution is Qualified with Alexa Voice Service

NXP Semiconductors has unveiled an MCU based voice control solution qualified with Amazon’s Alexa Voice Service (AVS). This enables original equipment manufacturers (OEMs) to quickly, easily and inexpensively add voice control to their products, giving their customers access to rich voice experiences with Alexa. Built on an NXP i.MX RT crossover platform, this MCU-based AVS solution enables low latency, far-field, “wake word” detection; embeds all necessary digital signal processing capabilities; runs on Amazon FreeRTOS; and includes an Alexa client application.
This MCU-based AVS solution provides OEMs with a self-contained, turnkey offering that enables them to quickly add Alexa to their products. It includes the MCU, the TFA9894D smart audio amplifier, optional A71CH secure element and comes with fully integrated software. It also features noise suppression, echo cancellation, beam forming and barge-in capabilities that enable use in acoustically difficult environments.

NXP offers at its Mougins, Sophia-Antipolis facilities a product testing service for Alexa Built-in products, available to its customers desiring to test their devices before submitting to Amazon for final evaluation. If a customer’s product supports music and/or is far-field enabled and uses a “wake word” to initiate interactions with Alexa, additional testing is required prior to submitting products to Amazon for evaluation. This is where Pro-Support Audio Voice Services helps to complete the self-test checklists.

NXP Semiconductors | www.nxp.com