About Circuit Cellar Staff

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

Hi-Fi Audio Engineering Workspace

Jan  Didden is a talented audio engineer and author with a well-stocked lab in Turnhout, Belgium. He recently gave us a tour of space and talked about his current audio design projects.

This is an excellent place to work. It is a converted army barrack so, being an old army man myself, I feel comfortable here. Above me there is the Tax department and one floor below there is a medical department. I am safe from all sides. I have two rooms, one for studying and listening and one for all the projects and equipment.L1070786

One  of his current  projects is an amplifier for electrostatic speakers.

An electrostatic speaker works with a very thin foil to make the air move. To get that thin foil moving you need to apply a high voltage. That is normally done with transformers that transform the low voltage audio signal from the amplifier to a higher value. But a transformer is not a linear component and can introduce all sorts of distortion to the signal. The solution is to make an amplifier that produces a high voltage output directly, but there are not many transistors capable of providing these high voltages.

He also described a project he might showcase on Kickstarter in the near future.

My other project is very interesting for people who are using computers for measurement and testing audio. They all use a sound card (internal or external) but these cards have a limitation on the input voltage. That is typically around the 1 V. The project I am working on is an ‘auto ranger.’ It automatically scales the signal to measure to the right input voltage for the sound card. I think a lot of people will like that and I hope to make this product available, perhaps by making it a Kickstarter project.

Renesas Electronics Europe and SEGGER Accelerate RX Ecosystem Expansion

Renesas Electronics Europe and SEGGER recently announced their collaboration to facilitate the expansion of Renesas’s RX Family of 32-bit microcontroller ecosystem through the adoption of SEGGER’s newly-released SystemView software. SystemView supports streaming over J-Link, as well as real-time analysis and visualization, in relation to any Renesas RX-based embedded design.Segger RS

SystemView gives you insight into the behavior of a program. It offers cycle accurate tracing of interrupts and task start/stop in addition to task activation and API calls when an RTOS is used. It visualizes and analyzes CPU load by task, interrupts, and software timers. Using SEGGER’s J-Link debug probe with SystemView enables real-time analysis, which gives you an in-depth understanding of the application’s run-time behavior.

SystemView uses SEGGER’s Real-Time Transfer (RTT) technology to ensure real-time delivery of data and minimal intrusiveness on the system. RTT enables up to 2 MB per second data transfer for continuous acquisition of real-time data, requiring no hardware other than a J-Link and the standard debug interface. SystemView records the data retrieved from the target and visualizes the results in different ways. You can save data recordings for later documentation and analysis.

SystemView works seamlessly with SEGGER’s RTOS embOS, which includes all the necessary recording capabilities. SystemView doesn’t require any OS involvement.

Source: SEGGER

STMicroelectronics Certifies Cryptographic Library for STM32 MCUs

STMicroelectronics has successfully certified its cryptographic library for STM32 microcontrollers as per the US Cryptographic Algorithm Validation Program (CAVP). An extension to the STM32Cube software package, the X-CUBE-CRYPTOLIB library is well suited for secure STM32-based applications, such as IoT devices, point-of-sale terminals, and smart meters.

The STM32 cryptographic library includes all the major security algorithms for encryption, hashing, message authentication, and digital signing. This enables you to meet application requirements for any combination of data integrity, confidentiality, identification/authentication, and non-repudiation. The library includes firmware and hardware-acceleration functions for some STM32 families.

There are examples for each algorithm and template projects for popular development tools such as Keil MDK-ARM, IAR Embedded Workbench EWARM, and GCC-based IDEs (e.g., Ac6 SW4STM32 and Atollic TrueSTUDIO).

The approved algorithms are AES (validation number 3971), RSA (2036), ECDSA (874), SHS (3275), DRBG (1165) and HMAC (2589). Full details are available online at the NIST CSRC Algorithm Validation Lists webpage. X-CUBE-CRYPTOLIB contains many further algorithms, including DES, TripleDES, MD5, ECC with key generation, ChaCha20, Poly1305, Curve25519 and others.

The X-CUBE-CRYPTOLIB for STM32 is available free of charge under the terms of STMicro’s Software License Agreement (SLA0048).

Source: STMicroelectronics

FTDI Arduino-Compatible Touch-Enabled Display Shield Now Shipping

FTDI Chip recently announced the widespread availability of its originally crowdfunded CleO product (and accompanying accessories). FTDI Chip also offers access to software tools, step-by-step tutorials, and projects. FTDI CleOCleO is a simple to program, intelligent TFT display solution that for building human machine interfaces (HMIs) with higher performance than typical Arduino display shields. The initial CleO includes an HVGA resolution, 3.5″ TFT display featuring a resistive touchscreen. An FTDI Chip FT810 high-resolution embedded video engine (EVE) graphic controller executes the HMI operation. An FTDI FT903 microcontroller handles all the additional processing tasks. The advanced display shield provides high-quality graphical animation, even at 60-fps frame rates. In addition, its antialiased graphics capabilities render images in finer detail.

When CleO is combined with FTDI Chip’s NerO—which is an energy-efficient Arduino design capable of operating up to 1 W—it offers a far more powerful solution than a normal Arduino UNO/display shield package.

CleO has an array of useful accessories:

  • AT 57.15 mm × 54.35 mm, the CleO-RIO module provides a mechanism for stacking the CleO shield and an Arduino board together.
  • The CleO-Speaker module (63 mm × 63 mm × 23.8 mm) facilitates the playback music/tones for HMIs where audio functionality has been incorporated. There is also an audio line for input of audio from external sources.
  • The CleO-Camera module has an OV5640 0.25″ 5-megapixel CMOS image sensor plus flash LEDs and a 24-pin 0.5-mm pitch FFC cable.
  • A 9-V power adaptor provides the NerO/CleO solution with up to 1 A of current.

The CleO costs $69. Refer to FTDI’s new forum, www.CleOstuff.com, for design tips, application ideas, and more.

Source: FTDI Chip

IEC Adopts USB Type-C, USB Power Delivery, & USB 3.1 Specs

The International Electrotechnical Commission (IEC) and USB Implementers Forum (USB-IF) recently announced that IEC has formally adopted the latest USB-IF specifications for high-speed data delivery and enhanced usages for device charging. In particular, the USB Type-C Cable and Connector, USB Power Delivery and USB 3.1 (SuperSpeed USB 10 Gbps) specifications. These specifications define a truly single-cable solution for audio/video, data, and power delivery.

The standards are expected to advance global action on reducing e-waste and improving the reusability of power supplies with a range of electronic devices. The IEC approach for ongoing standardization work in this space is driven by the ultimate goals of increasing external power supply re-usability, supporting consumer convenience, maintaining product reliability and safety, and providing for future technology innovations. In addition, widespread adoption of the resulting International Standards will help to reduce the encroachment of poorly designed or manufactured aftermarket substitutes which may affect the operation of electronic devices in compliance with regulatory requirements.USB

The IEC specification numbers :

  • IEC 62680-1-3 (USB Type-C)
  • IEC 62680-1-2 (USB PD)
  • IEC 62680-3-1 (USB 3.1)

The USB Type-C specification defines the physical USB Type-C cable and connector form factor to facilitate thinner and sleeker product designs, enhance usability and provide a growth path for performance enhancements for future versions of USB.

USB Power Delivery was developed to provide flexible, bi-directional power capabilities by enabling faster charging and increased power levels up to 100W. The USB Power Delivery specification defines standardized features that support the global adoption of interoperable power supplies, helping to reduce electronic waste and increase re-usability of adapters and chargers for consumer electronics.

USB 3.1 enables speeds up to 10 Gbps, supporting audio/video for USB hosts, hubs, and devices. Combined with USB Type-C, USB 3.1 and USB Power Delivery define a truly single-cable solution for audio/video, data and power delivery, building on the existing global ecosystem of USB/IEC 62680 series of International Standards compliant devices.

The International Electrotechnical Commission (IEC) brings together 166 countries, representing 98% of the world population and 96% of world energy generation, and close to 15,000 experts who cooperate on the global, neutral and independent IEC platform to ensure that products work everywhere safely with each other. The IEC is the world’s leading organization that prepares and publishes globally relevant International Standards for the whole energy chain, including all electrical, electronic and related technologies, devices and systems. The IEC also supports all forms of conformity assessment and administers four Conformity Assessment Systems that certify that components, equipment and systems used in homes, offices, healthcare facilities, public spaces, transportation, manufacturing, explosive environments and energy generation conform to them.

IEC work covers a vast range of technologies: power generation (including all renewable energy sources), transmission, distribution, Smart Grid & Smart Cities, batteries, home appliances, office and medical equipment, all public and private transportation, semiconductors, fiber optics, nanotechnology, multimedia, information technology, and more. It also addresses safety, EMC, performance, and the environment.

Source: International Electromechanical Commission

Debugging Embedded Systems with Minimal Resources

Debugging an embedded system can be difficult when you’re dealing with either a simple system with few pins or a complex system with nearly every pin in use. Stuart Ball provides some tips to make debugging such systems a little easier.

Debugging a microcontroller system can be difficult. Things don’t work right and it often isn’t even clear why. Was something initialized wrong? Is it a timing issue? Is there conflicting use of shared resources?

Debugging is more complicated when there are limited resources. If all the processor pins are used, what do you connect to? How do you get debug information out of the firmware so you can see what is going on?

This article isn’t about debugging when you have Ethernet, USB, and Bluetooth interfaces available, or when you have a full-speed emulator. This is about debugging when there aren’t many resources available—simple systems with few pins, or more complex systems with nearly every pin already used for something.

This is the schematic for a serial port RS-232 driver. It's a standardized circuit that plugs into a header on the board to be debugged.

Figure 1: This is the schematic for a serial port RS-232 driver. It’s a standardized circuit that plugs into a header on the board to be debugged.

Postmortem vs. Real-Time Debugging

There are two general ways of debugging an embedded system. One is postmortem, looking at the state of the system after it has failed or after it has stopped at a breakpoint. The other is real-time, debugging while the system is running. Each has its own place and its own set of challenges.

Generally, the two methods use different debug techniques. A postmortem debug happens when the motor is stalled, the software can’t recover, and you have no idea why it happened. You want to know the system’s state and how it got there. Setting breakpoints is a method used in postmortem debugging; you stop the system and look at the static state after a particular point in the code is reached.

Real-time or active debugging is more appropriate for looking at timing issues, missed interrupts, cumulative latency issues, and cases where the system just does occasionally does something strange but doesn’t actually stop. Real-time debug can tell you how the system got into the state that you are trying to analyze using postmortem methods. If you can capture enough information while the system is running, you have a chance to turn a real-time problem into a simpler static post-mortem analysis.

This article appears in Circuit Cellar 312, July 2016. Download the complete article.

Universal Debug Solution

An asynchronous serial port may be the most common debug tool used in the embedded world. Most microcontrollers have at least one serial port built in. The serial port has limitations. Its speed is limited and it requires level translation to connect it to the RS-232 voltage levels of a PC.

In many cases, you might not want to put the RS-232 driver on your board. You don’t want to use the space required by either the IC or the RS-232 connector, especially for something that is only used while debugging. One way I’ve solved this problem is shown in Figure 1, which depicts just a Maxim Integrated (or Texas Instruments) MAX3232 RS-232 driver IC connected to a DE9 connector. The other side connects to a four-pin header. This is connected via a cable to the embedded system to be tested. This allows the embedded system to have just the four-pin connector wired to the microcontroller serial port pins, power, and ground.

You plug in the external circuit when you need to debug and unplug it when you are done. There is nothing special about this circuit, it is exactly the same as you might put on your microcontroller board. Except you don’t need the space on your board for this. The circuit takes power from the microcontroller board via pins 1 and 4 of the four-pin Molex connector. The connector indicated is polarized so you can’t plug it in backward. I’ve standardized on this in my embedded systems at least where the serial port is used for debug or download.

Although I used a connector with 0.1” centers on the interface board, there is nothing to prevent you from using a 2 mm or 0.05” connector, or even a row of pads at the edge of the board being debugged. You just have to make a cable that has the Molex connector at one end and whatever you need to match your embedded board at the other end. You can keep the driver board in your toolbox, put the connector on your embedded system boards, and you have it when you need it.

You can house the board into a plastic project box. In one case, I built one on a narrow piece of perforated project board, and covered the entire thing in heat shrink tubing. It has the right-angle Molex connector on one end, and a short cable with the RS-232 connector on the other end. I keep that one in my desk drawer at work.

Read the entire article (PDF)

Industry’s First Open-Source SoC Platforms

SiFive recently introduced the Freedom family of system on a chip (SoC) platforms that are built around the open-source RISC-V instruction set architecture, which was developed by the company’s founders at the University of California, Berkeley.

Features and specs:

  • Freedom U500 Series: The Freedom Unleashed (U) family features a fully Linux-capable embedded application processor featuring the world’s most advanced, multi-core RISC-V CPUs, running at a speed of 1.6 GHz or higher with support for accelerators and cache coherency. Designed in TSMC 28 nm, the Freedom U500 platform is well suited for machine learning, storage, and networking applications. The platform also supports standard high-speed peripherals including PCIe 3.0, USB 3.0, Gigabit Ethernet, and DDR3/DDR4.
  • Freedom E300 Series: The Freedom Everywhere (E) family is designed for embedded microcontroller, IoT, and wearables markets. Designed in TSMC 180 nm and architected to have minimal area and power, the Freedom E300 platform features efficient RISC-V cores with support for RISC-V compressed instructions that have been shown to reduce code size by up to 30%.

Full FPGA models of each SoC are now available. Visit dev.sifive.com for more information.

Source: SiFive

New Micro Buzzers for Portable Applications

CUI’s Components Group recently expanded its micro buzzer product line. Housed in surface-mount packages as small as 4 mm × 4 mm, the three new models—CMT 4023S SMT, CMT 5023S SMT, and CPT 9019S SMT—are well suited for a wide variety of portable electronic systems.
UCI buzzer

The CMT 4023S SMT and CMT 5023S SMT magnetic transducer buzzers are 4 mm × 4 mm and 5 mm × 5 mm, respectively. They have a rated voltage of 3 V and a rated frequency of 4 kHz.

The 9 mm × 9 mm CPT 9019S SMT features piezoelectric technology and a profile depth of 1.9 mm. The series delivers a maximum peak-to-peak voltage of 25 V, a rated frequency of 4 kHz, and an SPL of 65 dB. Its operating temperature range is –30°C to 70°C.

The CMT 4023S SMT, CMT 5023S SMT, and CPT 9019S SMT are externally driven and suitable for use in designs requiring reflow solder assembly for high-volume production. They are available immediately with prices starting at $1.08 per unit in 1,000-piece quantities.

Source: CUI

High-Performance Secure Shell Solution for MCU-Based Systems

SEGGER recently introduced its emSSH software library for the purpose of creating secure connections between a client and a server, typically over a TCP/IP connection. The library is well suited for applications such as secure remote controls.

emSSH includes all modules required for implementing SSH cryptographic networks. They are provided as source code and thus give complete code control. emSSH also delivers full transparency, which eliminates concerns about possible security issues. Its flexible crypto engine can make use of hardware acceleration (if available), and it comes with a powerful API.

Hardware and transport independent, emSSH integrates with SEGGER’s em-bOS/IP and third-party stacks via the standard socket interface. You can configure the emSSH library to meet a variety of speed or size requirements. Unused features can be excluded and additional features can easily be added. The complete software package is written in ANSI C and it’s both compiler and target independent.

Source: SEGGER Microcontroller

RF-LORA Module for the IoT

RF Solutions’s RF-LORA module is a high-performance radio module delivered in a compact 23 mm × 20 mm format. Intended for Internet of Things (IoT) applications, the RF-LORA module delivers Semtech’s LoRa technology for IoT applications.RF-LORA promo image v2 copy

The RF-LORA’s specs and features:

  • Up to 16 km, spread-spectrum communication and high interference immunity within minimum current consumption
  • Semtech SX1272 LoRa chip.
  • Built-in preamble detection
  • Available in SMT and DIL packages

Source: RF Solutions

Programmable Analog SoCs for Embedded IoT Apps

Cypress Semiconductor Corp. recently introduced a new PSoC that simplifies the design of next-generation, multiple-sensor systems. Based on a 32-bit ARM Cortex-M0+ signal processing engine, the Analog Coprocessor integrates programmable analog blocks, including a new Universal Analog Block (UAB), which can be configured with GUI-based software components. You can use it  to continuously monitor multiple sensors, such as temperature, humidity, ambient light, motion, and sound. You can handle future design changes to support new sensor types by reconfiguring the programmable analog blocks.Cypress CY8C-KIT

Cypress’s free PSoC Creator Integrated Design Environment (IDE) enables you to design custom sensor interfaces. You can simply configure the programmable analog blocks by dragging and dropping components on the PSoC Creator schematic and customizing them with graphical component configuration tools. The components offer fully engineered embedded initialization, calibration, and temperature correction algorithms.

Available in a 3.7 mm × 2 mm chip-scale package, the PSoC Analog Coprocessor is currently sampling. Production is slated for Q4 2016.

Source: Cypress Semiconductor Corp.

New FMEA-Compliant µModule Regulator

Linear Technology recently introduced the LTM8003 step-down DC/DC µModule regulator. With a 40-V input voltage rating and 3.5 A of continuous output current, the LTM8003’s pinout is failure mode effects analysis (FMEA) compliant, so the output voltage remains at or below the regulation voltage in the event of a short-circuit to GND, a short-circuit to a nearby pin, or if a pin is left floating.  Linear 8003

The LTM8003 operates in four operation: Burst Mode, pulse skip mode, pulse skip mode with spread spectrum, and external synch mode. The quiescent current in Burst Mode operation is 25 µA (max), which makes the LTM8003 a good option for battery-operated systems.

The LTM8003’s specs and features:

  • Wide Input Voltage Range: 3.4 to 40 V
  • Wide Output Voltage Range: 0.97 to 18 V
  • 3.5 A Continuous Output Current (6 A Peak)
  • FMEA-compliant pinout
  • 150°C maximum operating temperature (H-Grade)
  • Selectable switching frequency: 200 kHz to 3 MHz
  • External synchronization
  • Low quiescent current = 25 µA
  • Programmable soft-start
  • 6.25 mm × 9 mm × 3.32 mm BGA package

The LTM8003 starts at 1,000-piece pricing starts at $11.30 each in 1,000-piece quantities.

Source: Linear Technology

New Schematic Challenge (Sponsor: Technologic Sysetms)

Can you spot the error in this month’s schematic challenge (sponsored by Technologic Systems)? This your chance to put your technical skills to test. Find the error in the schematic for a shot to win prizes, such as a TS-7250-V2 High-Performance Embedded Computer or a Circuit Cellar Digital Subscription.

Find the error and submit your answer via the online submission form. Click to access the form.

Click to enlarge. Find the error and submit your answer via the online submission form.

Take the challenge now!

Find the Code Error: Take This Engineering Challenge (Sponsor: Programming Research)

Ready to put your programming skills to the test? Take the new Electrical Engineering Challenge (sponsored by Programming Research). Find the error in the code for a shot to win prizes, such as an Amazon Gift Card or a Circuit Cellar magazine digital subscription.

Click to enlarge. Find the error and submit your answer via the online submission form.

Click to enlarge. Visit the challenge page to access the submission form.

Take the challenge now!

A Smarter, Deeper Resource for Electronics Engineers (Sponsored)

It’s an exciting time to work with electronics. If you’re an engineer, there are opportunities to develop products as new technologies intersect and trends such as the Internet of Things (IoT) and wearables open up new possibilities.

This intersection also challenges engineers to be multi-disciplinary in their understanding of electronics, covering everything from memory and storage, to network and communications, to power supplies and batteries. While the internet is resplendent with all sorts of resources for the knowledge-hungry engineer, it’s easy to fall down a Google-search rabbit hole that leads deep into an aging message board. It’s easy to end up on a wild goose chase of stale links to outdated content.


This post brought to you by Arrow.com. The Arrow.com site is simple but expansive, pulling together resources on a wide array of components so that users spend more time doing than searching.


Arrow.com solves that problem by reducing the time engineers spend searching for information on their specific areas of interest. They do so by corralling together information on electronics across disciplines and where they intersect.

More Than Just Products

From a straightforward product perspective, Arrow.com is a repository of more than one million products, all searchable by keyword. Updated daily, it’s a treasure trove of everything from amplifiers, audio components and capacitors to transceivers, wires and cables. Drill deeper into product categories to find the specific component you’re looking for with detailed specifications with clear options on how to purchase that item.

If you already have item or aren’t sure you will need it, you can access a hoard of data sheets across product categories, as well a complete reference designs, which you can browse by application, end product or manufacturer. An added bonus: nearly a quarter of the designs on Arrow.com are interactive.

Insightful and Interactive

The site is not just about offering a great deal of static information about electronics – it’s also about providing insight and guidance for best practices so engineers can get the most from the datasheets and reference designs that are available to them.

Arrow.com also offers a wealth of articles, compiled by a team of experts who work in the everyday trenches of engineering. They don’t stop at covering the products and components listed on the site at a high level; they also provide insight into how to better incorporate them into your designs.

Articles cover issues around power, such as how to battery-power your Pi (by highlighting three ways to get around your precise 5V requirements), how to protect your system when lightening strikes or why you need power factor correction. If you’re into the hot area of IoT, you can learn about the inner workings of BAC sensors, industrial connectivity protocols or the relationship between AVX and IoT devices. Explore technology in sports or see how you do at Arrow Tech Trivia. And if you’re more of a visual learner, Arrow.com has you covered with a library of videos that include specific product insights, broad overviews and lab demos.

Get Your Motor Running

March 11, 2015. Photo by Ellen Jaskol.

March 11, 2015. Photo by Ellen Jaskol.

One segment that’s seeing even more electronics use is automotive. Cars are getting smarter, both in terms of the dashboard systems for the driver and throughout the vehicle. If you’re looking to build a better motor, Arrow has you covered. And it can give you some ideas that you may not have considered for innovative projects. Arrow.com’s IoT experts recently collaborated on modifying a car so that it can be controlled by head movements alone.

Arrow.com’s site is not just about imparting information. The Design Center offers tools to accelerate your design cycle. For example, the Arrow enVision tool helps engineers who want a simple block diagram or a full reference design, while the cloud-based Lighting Designer lets you design a complete LED lighting system in minutes. You can also find a specialist to help you out by connecting with one of nearly 200 engineers via the site.

While sometimes it’s fun to get lost clicking through sites to find resources to help you solve an electronics conundrum or discover a new way of doing something, deadlines mean it’s good to have a reliable online resource at your fingertips. Arrow’s easily navigable site pulls together a wide range of electronics information that makes it a first choice for engineers.

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