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.

Tuesday’s Newsletter: IoT Tech Focus

Coming to your inbox tomorrow: Circuit Cellar’s IoT Technology Focus newsletter. Tomorrow’s newsletter covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

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You’ll get your IoT Technology Focus newsletter issue tomorrow.

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Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Embedded Boards.(4/23) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

April has a 5th Tuesday, so we’re bringing you a bonus newsletter:
Automotive Electronics (4/30)  Automotive dashboard are evolving into so-called infotainment systems at the same time more of the car is being controlled by embedded  computing. That’s driving a need for powerful MCU-based solutions that support these trends. This newsletter looks at the latest technology trends and product developments in automotive electronics.

Analog & Power. (5/7) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (5/14) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

Tuesday’s Newsletter: Microcontroller Watch

Coming to your inbox tomorrow: Circuit Cellar’s Microcontroller Watch newsletter. Tomorrow’s newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your Microcontroller Watch newsletter issue tomorrow.

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Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

IoT Technology Focus. (4/16) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards.(4/23) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

April has a 5th Tuesday, so we’re bringing you a bonus newsletter:
Automotive Electronics (4/30)  Automotive dashboard are evolving into so-called infotainment systems at the same time more of the car is being controlled by embedded  computing. That’s driving a need for powerful MCU-based solutions that support these trends. This newsletter looks at the latest technology trends and product developments in automotive electronics.

Analog & Power. (5/7) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Tuesday’s Newsletter: Analog & Power

Coming to your inbox on Tuesday: Circuit Cellar’s Analog & Power newsletter. This newsletter content zeros in on the latest developments in analog and power technologies including ADCs, DACs, DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your Analog & Power newsletter issue tomorrow.

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Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Microcontroller Watch. (4/9) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

IoT Technology Focus. (4/16) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards.(4/23) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Next Newsletter: Embedded Boards

Coming to your inbox tomorrow: Circuit Cellar’s Embedded Boards newsletter. Tomorrow’s newsletter content focuses on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your
Embedded Boards newsletter issue tomorrow.

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Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Analog & Power. (4/2) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (4/9) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

IoT Technology Focus. (4/16) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Tuesday’s Newsletter: IoT Tech Focus

Coming to your inbox tomorrow: Circuit Cellar’s IoT Technology Focus newsletter. Tomorrow’s newsletter covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your IoT Technology Focus newsletter issue tomorrow.

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

Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Embedded Boards.(3/26) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Analog & Power. (4/2) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (4/9) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

Tuesday’s Newsletter: Microcontroller Watch

Coming to your inbox tomorrow: Circuit Cellar’s Microcontroller Watch newsletter. Tomorrow’s newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your Microcontroller Watch newsletter issue tomorrow.

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Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

IoT Technology Focus. (3/19) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards.(3/26) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Analog & Power. (4/2) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Tuesday’s Newsletter: Analog & Power

Coming to your inbox on Tuesday: Circuit Cellar’s Analog & Power newsletter. This newsletter content zeros in on the latest developments in analog and power technologies including ADCs, DACs, DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

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You’ll get your Analog & Power newsletter issue tomorrow.

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Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Microcontroller Watch. (4/9) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

IoT Technology Focus. (4/16) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards.(4/23) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Next Newsletter: Embedded Boards

Coming to your inbox tomorrow: Circuit Cellar’s Embedded Boards newsletter. Tomorrow’s newsletter content focuses on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your
Embedded Boards newsletter issue tomorrow.

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

Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Analog & Power. (3/5) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (3/12) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

IoT Technology Focus. (3/19) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Guitar Video Game Uses PIC32

Realism Revamp

While music-playing video games are fun, their user interfaces tend to leave a lot to be desired. Learn how these two Cornell students designed and built a musical video game that’s interfaced using a custom-built wireless guitar controller. The game is run on a Microchip PIC32 MCU and has a TFT LCD display to show notes that move across the screen toward a strum region.

By Jake Podell and Jonah Wexler

While many popular video games involve playing a musical instrument, the controllers used by the player are not the greatest. These controllers are often made of cheap plastic, and poorly reflect the feeling of playing the real instrument. We have created a fun and competitive musical video game, which is interfaced with using a custom-built wireless guitar controller (Figure 1 and Figure 2). The motivation for the project was to experiment with video game interfaces that simulate the real-world objects that inspired them.

Figure 1
Front of the guitar controller. Note the strings and plectrum.

Figure 2
Back of the guitar controller

The video game is run on a Microchip PIC32 microcontroller [1]. We use a thin-film-transistor LCD display (TFT) to display notes that move across the screen toward a strum region. The user plays notes on a wireless mock guitar, which is built with carbon-impregnated elastic as strings and a conducting plectrum for the guitar pick. The game program running on the PIC32 produces guitar plucks and undertones of the song, while keeping track of the user’s score. The guitar is connected to an Arduino Uno and Bluetooth control center, which communicates wirelessly to the PIC32.

The controller was designed to simulate the natural motion of playing a guitar as closely as possible. We broke down that motion on a real guitar into two parts. First, users select the sound they want to play by holding the appropriate strings down. Second, the users play the sound by strumming the strings. To have a controller that resembled a real guitar, we wanted to abide by those two intuitive motions.

Fret & Strum Circuits

At the top of the guitar controller is the fret board. This is where the users can select the sounds they want to play. Throughout the system, the sound is represented as a nibble (4 bits), so we use 4 strings to select the sound.

Each string works as an active-low push-button. The strings are made of carbon-impregnated elastic, which feels and moves like elastic but is also conductive. Each string was wrapped in 30-gauge copper wire, to ensure solid contact with any conductive surfaces. The strings are each connected to screws that run through the fret board and connect the strings to the fret circuit (Figure 3).

Figure 3
Complete controller circuit schematic (on guitar).

The purpose of the fret circuit is to detect changes in voltage across four lines. Each line is branched off a power rail and connected across a string to an input pin on an Arduino Uno. Current runs from the power rail across each string to its respective input pin, which reads a HIGH signal. To detect a push on the string, we grounded the surface into which the string is pushed. By wrapping the fret board in a grounded conductive pad and pushing the string into the fret board, we are able to ground our signal before it can reach the input pin. When this occurs, the associated pin reads a LOW signal, which is interpreted as a press of the string by our system.

Along with the fret circuit, we needed a way to detect strums. The strum circuit is similar in its use of a copper-wrapped, carbon-impregnated elastic string. The string is connected through the fret board to an input pin on the Arduino, but is not powered. Without any external contact, the pin reads LOW. When voltage is applied to the string, the pin reads HIGH, detecting the strum. To mimic the strumming motion most accurately, we used a guitar pick to apply the voltage to the string. The pick is wrapped in a conductive material (aluminum foil), which is connected to the power rail. Contact of the pick applies voltage to the string, which on a rising edge denotes a strum.

Figure 4
Shown here is a block diagram of the controller signals.

As shown in Figure 4, the direct user interface for the player is the guitar controller. The physical interaction with the guitar is converted to an encoded signal by an Arduino mounted to the back of the guitar. The Arduino Uno polls for a signal that denotes a strum, and then reads the strum pattern across the four strings. The signal is sent over USB serial to a Bluetooth control station, which uses a Python script to broadcast the signal to an Adafruit Bluetooth LE module. The laptop that we used as a Bluetooth control station established a link between the controller and the Bluetooth receiver, and was paramount to the debugging and testing of our system. Finally, the Bluetooth module communicated over UART with the PIC, which interpreted the user’s signal in the context of the game [2].  …

Read the full article in the March 344 issue of Circuit Cellar
(Full article word count: 3271 words; Figure count: 10 Figures.)

Watch the project video here:

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.

Tuesday’s Newsletter: IoT Tech Focus

Coming to your inbox tomorrow: Circuit Cellar’s IoT Technology Focus newsletter. Tomorrow’s newsletter covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your IoT Technology Focus newsletter issue tomorrow.

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Don’t be left out! Sign up now:

Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Embedded Boards.(2/26) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Analog & Power. (3/5) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (3/12) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

Tuesday’s Newsletter: Microcontroller Watch

Coming to your inbox tomorrow: Circuit Cellar’s Microcontroller Watch newsletter. Tomorrow’s newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your Microcontroller Watch newsletter issue tomorrow.

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

Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

IoT Technology Focus. (2/19) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards.(2/26) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Analog & Power. (3/5) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Tuesday’s Newsletter: Analog & Power

Coming to your inbox on Tuesday: Circuit Cellar’s Analog & Power newsletter. This newsletter content zeros in on the latest developments in analog and power technologies including ADCs, DACs, DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your Analog & Power newsletter issue tomorrow.

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

Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Microcontroller Watch. (2/12) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

IoT Technology Focus. (2/19) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards.(2/26) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Tinkering with Time

Protocols and Programming

Many embedded systems need to make use of synchronized time information. In this article, Jeff explores the history of time measurement and how it has led to NTP and other modern technologies for coordinating universal date and time. Using Arduino and the Espressif System’s ESP32, Jeff then goes through the steps needed to enable an embedded system to request, retrieve and display the synchronized date and time to a display.
(Caption for lead image Figure 1: Time zone boundaries are flexible, shifted locally to keep territories from being divided wherever possible..

By Jeff Bachiochi

It’s been said that ”If you are on time, you’re late,” or, “To be early is to be on time.” It’s all relative. If you go to a meeting and people are already there, you feel as if you are late. If you are the first to arrive, you wonder if you’ve got the schedule wrong, and then you check your watch or phone for the time. Time can be troublesome for us, because the present is an ever-changing instant where the past meets the future. We cruise through life when all players reference the same moment, but should we become out of sync, the ride gets bumpy.

We can imagine that in humanity’s early times the first concepts of time were cyclic periods—like day/night, seasons and life/death. Our fundamental measurement of a day directly relates to our life and history, and seems to tie all nature together. But what about those activities that occur within the confines of each day? Some way of defining the parts of a day were needed. At the time, we had one division—day/night—with most considering the start of a day to be daybreak or sunrise, and the start of night to be sunset.

Since daytime was directly related to the sun’s position, the day could be divided into two parts based on whether the sun was rising in the sky or falling back toward the horizon. Observing the sun’s shadow gave way to the first sundials, which provided a visual indication of time relative to sunrise and sunset without physical divisions. One such division of the day was religious in origin: canonical hours or periods of fixed prayer at regular intervals were defined in monastic communities. At that time, our understanding of the sky was astrological and not astronomical. The latter would eventually define the breakdown of a day into hours, minutes and seconds.

For the most part, the hour was a variable concept. Around the 14th century, 12 was chosen as a practical division of the day (and the night) into equal parts. It was the most convenient number for dividing into fractions because it’s divisible by 2, 3 and 4—thus giving us the 24-hour day we use today. Without the sun, sundials were worthless, so other means of recording the passage of time were invented, including water, candles and weights. These and early mechanical clocks of the 16th century were not accurate, because their mechanisms were essentially unregulated. It wasn’t until the next century that the pendulum gave the mechanical clock accuracy to within 1 minute a day. Today, we have access to extremely accurate clocks. Atomic clocks measure an atom’s fluctuating energy levels to produce an accuracy of ± 1 second in over a billion years.

Time Keeper

The International Bureau of Weights and Measures (called Bureau International des Poids et Mesures or BIPM in France) is an intergovernmental organization that was established to oversee measurement science and measurement standards. One important role for the BIPM is maintaining the accuracy of worldwide time of day. It combines, analyzes and averages the official atomic time standards of member nations around the world, to create a single, official Coordinated Universal Time (UTC). The Royal Observatory, Greenwich, England was chosen as the reference point to define the Universal day, counted from 0 hours at mean midnight, as used on the island since 1847. By 1884, the Greenwich Meridian was used for two-thirds of all charts and maps as their Prime Meridian. The world is divided into 24 time zones, each 15 degrees in width (24 hr/360 degrees). However, as shown in Figure 1, time zone boundaries are shifted to prevent a country from being needlessly split into separate zones.

All time on earth is related to the official time in Greenwich, England by denoting a time zone offset. Current civil time can be determined by adding or subtracting the UTC offset (number of hours and minutes). This ranges from UTC−12:00 in the west to UTC+14:00 in the east. Table 1 lists those offsets that relate to the United States.
The US spans seven time zones. When a time zone uses daylight saving time, the ST for Standard Time is replaced by DT indicating Daylight Saving Time. Daylight Saving Time increases the regional offset by 1:00, and was implemented to shift daylight activities during the longer summer hours. Daylight Saving Time is a local shift that must be handled locally, and as such does not affect the UTC in any way.

Table 1
Time zone offsets are listed here for the US daylight saving times have an additional offset of 1 hour and must be accounted for locally.

In my youth I recall the phone company providing a number you could to call to hear the current time. The first radio station, WWV in Colorado, morphed into National Institute of Standards and Technology (NIST), whose broadcast focused on developing frequency standards and eventually broadcasting time and frequency information on the 2.5-, 5-, 10-, 15- and 20-MHz shortwave bands. Today, the time is available almost everywhere, and that time is synchronized to the UTC, all thanks to the Internet.

National Standard Time

The Network Time Protocol (NTP) is used to synchronize our clocks via the Internet. The NTP architecture, protocol and algorithms provide a nominal accuracy of tens of milliseconds on WANs, sub-milliseconds on LANs, and sub-microseconds using a precision time source such as a cesium oscillator or GPS receiver. Reliability is assured by redundant tiered servers and diverse network paths. The “NTP pool” is a dynamic collection of networked computers that volunteer to provide highly accurate time via the NTP to clients (like us) worldwide. We can use one of the NTP pool servers to get UTC information. Although using the NTP protocol will assure the accuracies listed above, this is often unnecessary and overly complicated for those applications that are only interested in whole-second times for RTC (Real Time Clocks). SNTP, a simplified subset of the NTP protocol, generally is sufficient for our needs.

Figure 2
This is the format of the 48 byte packet sent to and from NTP servers. We can get away with sending a packet of “zero” data, except for the first byte as a request. A received packet will contain the total seconds since the Epoch located in the first four bytes of the Transmit Timestamp.

SNTP uses a UDP connection to send a datagram or packet, as opposed to a TCP connection. The basic transaction is simple. We send an SNTP data structure as a UDP packet using port 123 to the server. The time server (one of the NTP pool) then sends back an SNTP data structure as a UDP packet. That’s it! The structure of the datagram consists of four 32-bit words (4 × 32 bits = 128 bits or 16 bytes), followed by four 64-bit time stamps (4 × 64 bits = 256 b or 32 bytes) as shown in Figure 2. There can be optional data, but we won’t need it. In fact, we need only to worry about the first byte of the (16 bytes + 32 bytes = 48 bytes) datagram to make a request.

This is set according to RFC 4330:

LeapsecondInformation 2 bits = “00” disregarded
             VersionNumber 3 bits = “100” 4
                        MODE 3 bits = “011” Client
Therefore:
First Byte = “00100011” or 0x23

The returned datagram will be in the same format. The time stamps we sent as zeros could have been used to determine the actual propagation delay in the message trip, to calculate an accurate sub-second synchronized time. We are not concerned with that level of accuracy. However, we do want to get the time from the server, and that will be populated in the last of the four time stamps in the reply. So how does this time stamp relate to the present second, minute, hour, day, month and year? Sad to say, it does not specify any of those. This time stamp gives the number of seconds from 0:00 on 1 January 1900. …

Read the full article in the February 343 issue of Circuit Cellar
(Full article word count: 3269 words; Figure count: 5 Figures.)

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.

Next Newsletter: ICs for Consumer Electronics

Coming to your inbox tomorrow: Circuit Cellar’s ICs for Consumer Electronics newsletter. Today’;s consumer electronic product designs demand ICs that enable low-power, high-functionality and cutthroat costs. Today’s microcontroller, analog IC and power chip vendors are laser-focused on this lucrative, high-stakes market. This newsletter looks at the latest technology trends and product developments in for consumer electronics ICs.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

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ICs for Consumer Electronics newsletter issue tomorrow.

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Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Analog & Power. (2/5) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (2/12) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

IoT Technology Focus. (2/19) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.