Texting and IoT Embedded Devices (Part 1)

Fun with the ESP8266 SoC

Can texting be leveraged for use in IoT Wi-Fi devices? Jeff has been using Wi-Fi widgets for a lot of IoT projects lately. This month Jeff lays the groundwork for describing a project that will involve texting. He starts off with a look at Espressif System’s ESP8266EX SoC.

By Jeff Bachiochi

Believe it or not, texting while driving as of this writing is still legal in a few states. About 10% of all motor vehicles deaths in the US can be traced back to distracted drivers. Granted that includes any distraction—however cell phone distraction has quickly become a serious issue. While hazards exist for any technology, common sense should tell you this is a dangerous act.

When the technology is used correctly, texting can deliver essential information quickly—without requiring both (or many) parties to be active at the same time. This allows you to make better use of your time. I still use email for much of my correspondence, however it’s great to be able to send your spouse a text to add milk to the grocery list—after they’ve already left for the store! And even though I chuckle when I see two people sitting next to each other texting, it is a sad commentary on emerging lifestyles.

I’ve been using Wi-Fi widgets for a lot of IoT projects lately. The cost to enter the fray is low, and with free tools it’s easy to get started. This month’s article is a about a project that will involve text, even though that may not be apparent at first. Let’s start off slowly, laying the groundwork for those who have been thinking about building this kind of project. We’ll then quickly build from this foundation into crafting a useful gadget.

A Look at the ESP8266EX

The innovative team of chip-design specialists, software/firmware developers and marketers at Espressif System developed and manufactures the ESP8266EX system-on-chip (SoC). This 32-bit processor runs at 80 MHz and embeds 2.4 GHz Wi-Fi functionality—802.11 b/g/n, supporting WPA/WPA2—as well as the normal gamut of general-purpose I/O and peripherals. It has a 64 KB boot ROM, 64 KB instruction RAM and 96 KB data RAM. Their WROOM module integrates the ESP8266 with a serial EEPROM and an RF front end with a PCB antenna for a complete IoT interface.

Anyone who has ever used a dial-up modem is most likely familiar with the term AT command set. The Hayes command set is a specific command language originally developed in 1981 by Dennis Hayes for the Hayes 300 baud Smartmodem. Each command in the set begins with the letters AT+ followed by a command word used for high-level control of internal functions. For the modem these enabled tasks like dialing the phone or sending data. As an application for the WROOM, an AT command set seemed like a perfect match. This allows an embedded designer to use the device to achieve a goal without ever having to “get their hands dirty.”

This photo shows the ESP-01 and ESP-07 modules along with the FTDI 232 USB-to-serial converter used for programming either module.

I first learned of the ESP8266 years ago and purchased the ESP-01 on eBay. It was around $5 at the time (Photo 1). I used it along with the MEGA 2560—my favorite Arduino module because of its high number of I/Os and multiple hardware UARTs. With the ESP-01 connected to a serial port on an Arduino, an application could directly talk with the ESP-01 and get the Arduino connected to your LAN. From this point, the world is under your control thanks to the AT Wi-Fi and TCP commands.

The ESP8266 literature states the Wi-Fi stack only requires about 20% of the processing power. Meanwhile, 80% is still available for user application programming and development.
So why not eliminate the Arduino’s Atmel processor altogether and put your Arduino code right in the 8266? Espressif Systems has an SDK and while it provides a development and programming environment, the Arduino IDE is comfortable for many. And it offers the installation of third-party platform packages using the Boards Manager. That means you can add support for the ESP8266EX and use much of the code you’ve already written.

Using the ESP-01

Since the ESP-01 has only 8 pins, adding the necessary hardware is pretty simple. This low power device runs on 2.5 V to 3.6 V, so you must make appropriate level corrections if you wish to use it with 5 V devices like Arduino boards. …

Read the full article in the March 332 issue of Circuit Cellar

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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.

IoT: From Device to Gateway

Modules for the Edge

Connecting to the IoT edge requires highly integrated technology, blending wireless connectivity and intelligence. Feeding those needs, a variety of IoT modules have emerged that offer pre-certified solutions that are ready to use.

By Jeff Child, Editor-in-Chief

he Internet of Things (IoT) is one of the most dynamic areas of embedded systems design today. Opportunities are huge as organizations large and small work to develop IoT implementations. IoT implementations are generally comprised of three main parts: the devices in the field, the cloud and the network (gateways) linking them together. This article focuses on the “things” side—in other words, the smart, connected edge devices of the IoT. For more on IoT gateways, see “IoT Gateway Advances Take Diverse Paths“ (Circuit Cellar 328, November 2017).

Because this sub-segment of technology is growing and changing so fast, it’s impossible to get a handle on everything that’s happening. The scope that comprises IoT edge devices includes a combination of embedded processors and microcontrollers that provide intelligence. It also includes various wireless, cellular and other connectivity solutions to connect to the network. And it includes sensors to collect data and battery technologies to keep the devices running.

Connecting the various nodes of an IoT implementation can involve a number of wired and wireless network technologies. But it’s rare that an IoT system can be completely hardwired end to end. Most IoT systems of any large scale depend on a variety of wireless technologies including Wi-Fi, Bluetooth, Zigbee and even cellular networking.

What’s most interesting among all that, are not those individual pieces themselves, but rather an emerging crop of modular IoT products that combine intelligence and connectivity, while also taking on the vital certifications needed to get IoT implementations up and running. With all that in mind, the last 12 months have seen an interesting mix of module-based products aimed directly at IoT.

Certified IoT Modules

Exemplifying those trends, in September 2017, STMicroelectronics (ST)introduced the SPBTLE-1S, a ready-to-use Bluetooth Low Energy (BLE) module that integrates all the components needed to complete the radio subsystem (Photo 1). The BLE module integrates ST’s proven BlueNRG-1 application-processor SoC and balun, high-frequency oscillators and a chip antenna.

Photo 1
The SPBTLE-1S is a BLE module that integrates all the components needed to complete the radio subsystem. It’s BQE-approved, and FCC, IC and CE-RED certified to simplify end-product approval for North America and EU markets.

Developers can use this module to bypass hardware design and RF-circuit layout challenges. The SPBTLE-1S is BQE-approved, and FCC, IC and CE-RED (Radio Equipment Directive) certified to simplify end-product approval for North America and EU markets. ST’s Bluetooth 4.2 certified BLE protocol stack is included, and the supporting Software-Development Kit (SDK) contains a wide range of Bluetooth profiles and sample application code.

The device is packaged in a space-efficient 11.5 mm x 13.5 mm outline and has a wide supply-voltage range of 1.7 V to 3.6 V. The SPBTLE-1S module is well suited for small, battery-operated objects powered by various types of sources such as a primary button cell or rechargeable Li-ion battery. High RF output power of +5 dBm and good receiver sensitivity help to maximize communication range and reliability.

The BlueNRG-1 SoC at the heart of the SPBTLE-1S implements the complete BLE physical layer (PHY), link layer and network/application-processing engine comprising a low-power ARM Cortex-M0 core with 160 KB flash, 24 KB RAM with data retention and a security co-processor. The SoC also implements smart power management, with a DC/DC converter capable of powering the SPBTLE-1S module to ensure optimum energy efficiency. Users can leverage an extensive set of interfaces, including a UART, two I²C ports, SPI port, single-wire debug and 14 GPIOs, as well as peripherals including two multifunction timers, a 10-bit ADC, watchdog timer and real-time clock and a DMA controller. There is also a PDM stream processor interface, which is ideal for developing voice-controlled applications.

IoT Module for Development

Riding the IoT wave, all the major microcontroller vendors have beefed up their module-based IoT solutions in order to make it easier for developers to design in their MCUs. One example along those lines is the LPC54018 IoT module, developed by NXP in partnership with Embedded Artists. …

Read the full article in the March 332 issue of Circuit Cellar

Don’t miss out on upcoming issues of Circuit Cellar. Subscribe today!
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.

March Circuit Cellar: Sneak Preview

The March issue of Circuit Cellar magazine is coming soon. And we’ve got a healthy serving of embedded electronics articles for you. Here’s a sneak peak.

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Here’s a sneak preview of March 2018 Circuit Cellar:

TECHNOLOGY FOR THE INTERNET-OF-THINGS

IoT: From Device to Gateway
The Internet of Things (IoT) is one of the most dynamic areas of embedded systems design today. This feature focuses on the technologies and products from edge IoT devices up to IoT gateways. Circuit Cellar Chief Editor Jeff Child examines the wireless technologies, sensors, edge devices and IoT gateway technologies at the center of this phenomenon.

Texting and IoT Embedded Devices
Texting has become a huge part of our daily lives. But can texting be leveraged for use in IoT Wi-Fi devices? Jeff Bachiochi lays the groundwork for describing a project that will involve texting. In this part, he gets into out the details for getting started with a look at Espressif System’s ESP8266EX SoC.

Exploring the ESP32’s Peripheral Blocks
What makes an embedded processor suitable as an IoT or home control device? Wi-Fi support is just part of the picture. Brian Millier has done some Wi-Fi projects using the ESP32, so here he shares his insights about the peripherals on the ESP32 and why they’re so powerful.

MICROCONTROLLERS HERE, THERE & EVERYWHERE

Designing a Home Cleaning Robot (Part 4)
In this final part of his four-part article series about building a home cleaning robot, Nishant Mittal discusses the firmware part of the system and gets into the system’s actual operation. The robot is based on Cypress Semiconductor’s PSoC microcontroller.

Apartment Entry System Uses PIC32
Learn how a Cornell undergraduate built a system that enables an apartment resident to enter when keys are lost or to grant access to a guest when there’s no one home. The system consists of a microphone connected to a Microchip PIC32 MCU that controls a push solenoid to actuate the unlock button.

Posture Corrector Leverages Bluetooth
Learn how these Cornell students built a posture corrector that helps remind you to sit up straight. Using vibration and visual cues, this wearable device is paired with a phone app and makes use of Bluetooth and Microchip PIC32 technology.

INTERACTING WITH THE ANALOG WORLD

Product Focus: ADCs and DACs
Makers of analog ICs are constantly evolving their DAC and ADC chips pushing the barriers of resolution and speeds. This new Product Focus section updates readers on this technology and provides a product album of representative ADC and DAC products.

Stepper Motor Waveforms
Using inexpensive microcontrollers, motor drivers, stepper motors and other hardware, columnist Ed Nisley built himself a Computer Numeric Control (CNC) machines. In this article Ed examines how the CNC’s stepper motors perform, then pushes one well beyond its normal limits.

Measuring Acceleration
Sensors are a fundamental part of what make smart machines smart. And accelerometers are one of the most important of these. In this article, George Novacek examines the principles behind accelerometers and how the technology works.

SOFTWARE TOOLS AND PROTOTYPING

Trace and Code Coverage Tools
Today it’s not uncommon for embedded devices to have millions of lines of software code. Trace and code coverage 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 trace and code coverage tools.

Manual Pick-n-Place Assembly Helper
Prototyping embedded systems is an important part of the development cycle. In this article, Colin O’Flynn presents an open-source tool that helps you assemble prototype devices by making the placement process even easier.

January Circuit Cellar: Sneak Preview

The January issue of Circuit Cellar magazine is coming soon. And it’s got a robust selection of embedded electronics articles for you. Here’s a sneak peak.

Not a Circuit Cellar subscriber?  Don’t be left out! Sign up today:

 

Here’s a sneak preview of January 2018 Circuit Cellar:

 

                                     IMPROVING EMBEDDED SYSTEM DESIGNS

Special Feature: Powering Commercial Drones
The amount of power a commercial drone can draw on has a direct effect on how long it can stay flying as well as on what tasks it can perform. Circuit Cellar Chief Editor Jeff Child examines solar cells, fuel cells and other technology options for powering commercial drones.

CC 330 CoverFPGA Design: A Fresh Take
Although FPGAs are well established technology, many embedded systems developers—particularly those used the microcontroller realm—have never used them before. In this article, Faiz Rahman takes a fresh look a FPGAs for those new to designing them into their embedded systems.

Product Focus: COM Express boards
COM Express boards provide a complete computing core that can be upgraded when needed, leaving the application-specific I/O on the baseboard. This brand new Product Focus section updates readers on this technology and provides a product album of representative COM Express products.

TESTING, TESTING, 1, 2, 3

LF Resonator Filter
In Ed Nisley’s November column he described how an Arduino-based tester automatically measures a resonator’s frequency response to produce data defining its electrical parameters. This time he examines the resultsand explains a tester modification to measure the resonator’s response with a variable series capacitance.

Technology Spotlight: 5G Technology and Testing
The technologies that are enabling 5G communications are creating new challenges for embedded system developers. Circuit Cellar Chief Editor Jeff Child explores the latest digital and analog ICs aimed at 5G and at the test equipment designed to work with 5G technology.

                                     MICROCONTROLLERS IN EVERYTHING

MCU-based Platform Stabilizer
Using an Inertial Measurement Unit (IMU), two 180-degree rotation servos and a Microchip PCI MCU, three Cornell students implemented a microcontroller-based platform stabilizer. Learn how they used a pre-programmed sensor fusion algorithm and I2C to get the most out of their design.

Designing a Home Cleaning Robot (Part 2)
Continuing on with this four-part article series about building a home cleaning robot, Nishant Mittal this time discusses the mechanical aspect of the design. The robot is based on Cypress Semiconductor’s PSoC microcontroller.

Massage Vest Uses PIC32 MCU
Microcontrollers are being used for all kinds of things these days. Learn how three Cornell graduates designed a low-cost massage vest that pairs seamlessly with a custom iOS app. Using the Microchip PIC32 for its brains, the massage vest has sixteen vibration motors that the user can control to create the best massage possible.

AND MORE FROM OUR EXPERT COLUMNISTS:

Five Fault Injection Attacks
Colin O’Flynn returns to the topic of fault injection security attacks. To kick off 2018, he summarizes information about five different fault injection attack stories from 2017—attacks you should be thinking about as an embedded designer.

Money Sorting Machines (Part 2)
In part 1, Jeff Bachiochi delved into the interesting world of money sort machines and their evolution. In part 2, he discusses more details about his coin sorting project. He then looks at a typical bill validator implementation used in vending systems.

Overstress Protection
Last month George Novacek reviewed the causes and results of electrical overstress (EOS). Picking up where that left off, in this article he looks at how to prevent EOS/ESD induced damage—starting with choosing properly rated components.

Antenna Measurement Made Easy

For web Lacoste Lead Image

Covering the Basics

If you’re doing any kind of wireless communications application, that probably means including an antenna in your design. The science of antennas is complex. But here Robert shows how the task of measuring an antenna’s performance is less costly and exotic than you’d think.

By Robert Lacoste

Now that wireless communications is ubiquitous, chances are you’ll be using Bluetooth, Wi-Fi, cellular, LoRa, MiWi or other flavor of wireless interface in your next design. And that means including an antenna. Unfortunately, antenna design is not an easy topic. Even very experienced designers sometimes have had to wrestle with unexpected bad performances by their antennas. Case in point: Google “iPhone 4 antenna problem” and you will get more than 3 million web pages! In a nutshell, Apple tried to integrate a clever antenna in that model that was threaded around the phone. They didn’t anticipate that some users would put their fingers exactly where the antenna was the most sensitive to detuning. Was it a design flaw? Or a mistake by the users? It was hotly debated, but this so-called “Antennagate” probably had significant impact on Apple’s sales for a while.

I already devoted an article to antenna design and impedance matching (“The Darker Side: Antenna Basics”, Circuit Cellar 211, February 2008). Whether you include a standard antenna or design your own, you will never be sure it is working properly until you measure its actual performance. Of course, you could simply evaluate how far the system is working. But how do you go farther if the range is not enough? How do you figure out if the problem is coming from the receiver, the transmitter, propagation conditions or the antenna itself? My personal experience has been that the antenna is very often the culprit. With that in mind, it really is mandatory to measure whether or not an antenna is behaving correctly. Take a seat. This month, I will explain how to easily measure the actual performance of an antenna. You will see that the process is quite easy and that it won’t even need costly or exotic equipment.

SOME ANTENNA BASICS

Let’s start with some basics on antennas. First, all passive antennas have the same performance whether transmitting or receiving. For this article, I’ll consider the antenna as transmitting because that’s easier to measure. Let’s consider an antenna that we inject with a given radio frequency power Pconducted into its connector. Where will this power go? First off, impedance matching should be checked. If the impedance of the antenna is not well matched to the impedance of the power generator, then a part of the power will be reflected back to the generator. This will happen in particular when the transmit frequency is not equal to the resonant frequency of the antenna. In such a case, a part of Pconducted will be lost.  That is known as mismatch losses: Pavailable= Pconducted – MismatchLosses. While that itself is a very interesting subject, I have already discussed impedance matching in detail in my February 2008 article. I also devoted another article to a closely linked topic: standing waves. Standing waves appear when there is a mismatch. The article is “The Darker Side: Let’s play with standing waves” (Circuit Cellar 271, February 2013).

For the purpose of discussion here, I will for now assume that there isn’t any mismatching—and therefore no mismatch loss. …

Read the full article in the October 327 issue of Circuit Cellar

We’ve made the October 2017 issue of Circuit Cellar available as a 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.
Don’t miss out on upcoming issues of Circuit Cellar. Subscribe today!

Small Plug-In Embedded Cellular Modem

Skywire plug-in modem

Skywire plug-in modem

The Skywire is a small plug-in embedded cellular modem. It uses a standard XBee form factor and 1xRTT CDMA operating mode to help developers minimize hardware and network costs. Its U.FL port ensures antenna flexibility.

The Skywire modem features a Telit CE910-DUAL wireless module and is available with bundled CDMA 1xRTT data plans from leading carriers, enabling developers to add fully compliant cellular connectivity without applying for certification. Future versions of the Skywire will support GSM and LTE. Skywire is smaller than many other embedded solutions and simple to deploy due to its bundled carrier service plans.

Skywire is available with a complete development kit that includes the cellular modem, a baseboard, an antenna, a power supply, debug cables, and a cellular service plan. The Skywire baseboard is an Arduino shield, which enables direct connection to an Arduino microcontroller.

Skywire modems cost $129 individually and $99 for 1,000-unit quantities. A complete development kit including the modem costs $262.

NimbeLink, LLC
www.nimbelink.com