Don’t Miss Our Newsletter: IoT Technology Focus

In tommorrow’s IoT Technology Focus newsletter you’ll get news and trends about the products and technologies needed to build IoT implementations and devices.LoRa-NNNCo-PR-graphic-press

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” themed newsletter issue tomorrow.

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

Remember, our new enhanced weekly CC Newsletter will switch its theme each week, so look for these in upcoming weeks:

Embedded Boards. This content looks at embedded board-level computers. The focus here is on modules—Arduino, Raspberry Pi, COM Express, and other small-form-factor —that ease prototyping efforts and let you smoothly scale up production volumes.

Analog & Power. 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. 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.

…and…

August has a 5th Tuesday. So look for a bonus Newsletter this  month!

Don’t Miss Our Newsletter: Microcontroller Watch

In tommorrow’s Microcontroller Watch we’ll feature key updates on the latest microcontroller technology  — the latest MCU design wins — new MCU product announcements — MCU industry events –and more.35352057604_77bb4aab93_m

Plus: 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” themed newsletter issue tomorrow.

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

Remember, our new enhanced weekly CC Newsletter will switch its theme each week, so look for these in upcoming weeks:

IoT Technology Focus. The Internet-of-Things (IoT) phenomenon is rich with opportunity. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards. This content looks at embedded board-level computers. The focus here is on modules—Arduino, Raspberry Pi, COM Express, and other small-form-factor —that ease prototyping efforts and let you smoothly scale up production volumes.

Analog & Power. 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.

…and…

August has a 5th Tuesday. So look for a bonus Newsletter this  month!

Don’t Miss Circuit Cellar’s Analog & Power Newsletter

Analog & Power is where stuff gets real. Converting signals to and from analog is how embedded devices interact with the real world. And without power supplies and power conversion, electronic systems can’t do anything. Circuit Cellar’s Analog & Power MFG_IB048E096T40N1-00themed newsletter is coming to your inbox tomorrow.

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.

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

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

Remember, our new enhanced weekly CC Newsletter will switch its theme each week, so look for these in upcoming weeks:

Microcontroller Watch. 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. The Internet-of-Things (IoT) phenomenon is rich with opportunity. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards. This content looks at embedded board-level computers. The focus here is on modules—Arduino, Raspberry Pi, COM Express, and other small-form-factor —that ease prototyping efforts and let you smoothly scale up production volumes.

Don’t Miss Circuit Cellar’s Newsletter: Embedded Boards

Board-level embedded computers are a critical building block around which system developers can build all manor of intelligent systems. Circuit Cellar’s Embedded Boards themed newsletter is coming to your inbox tomorrow. COM Express mm

The focus here is on module types like Arduino, Raspberry Pi, COM Express, and other small-form-factor modules that ease prototyping efforts and let you smoothly scale up to production volumes.

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

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

Remember, our new enhanced weekly CC Newsletter will switch its theme each week, so look for these in upcoming weeks:

Analog & Power. 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. 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. The Internet-of-Things (IoT) phenomenon is rich with opportunity. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

The Most Technical

Input Voltage

–Jeff Child, Editor-in-Chief

JeffHeadShotIt is truly a thrill and an honor for me to be joining the Circuit Cellar team as the magazine’s new Editor-in-Chief. And in this—my first editorial in my new role—I want to seize the opportunity to talk about Circuit Cellar. A lot of factors attracted me to this publication. But in a nutshell its position in the marketplace is compelling. It intersects with two converging trends happening in technology today.

First, there’s the phenomenon of the rich set of tools, chips, and information resources available today. They put more power into the hands of makers and electronics DIY experts than ever before. You’ve got hardware such as Arduino and Raspberry Pi. Open source software ranging from Linux to Eclipse make integrating and developing software easier than ever. And porting back and forth between open source software and commercial embedded software is no longer prohibitive now that commercial software vendors are in a “join them, not beat them” phase of their thinking. Easy access has even reached processors thanks to the emergence of RISC-V for example (click here for more). Meanwhile, powerful FPGA chips enable developers to use one chip where an entire board or box was previously required.

The second big trend is how system-level chip technologies—like SoC-style processors and the FPGAs I just mentioned—are enabling some of the most game-changing applications driving today’s markets: including commercial drones, driverless cars, Internet-of-Things (IoT), robotics, mobile devices and more. This means that exciting and interesting new markets are attracting not just big corporations looking for high volume play, but also small start-up vendors looking to find their own niche within those market areas. And there are a lot of compelling opportunities in those spaces. Ideas that start as small embedded systems projects can—and are—blossoming into lucrative new enterprises.

What’s so exciting is that Circuit Cellar readers are at the center of both those two trends. There’s a particular character this magazine has that separates it from other technology magazines. There are a variety of long-established publications that cover electronics and whose stated missions are to serve engineers. I’ve worked for some of them, and they all have their strengths. But you can tell just by looking at the features and columns of Circuit Cellar that we don’t hold back or curtail our stories when it comes to technical depth. We get right down to the bits and bytes and lines code. Our readers are engineers and academics who want to know not only the rich details of a microcontroller’s on-board peripherals, but also how other like-minded geeks applied that technology to their DIY or commercial project. They want to know if the DC-DC converter they are considering has a wide enough input voltage to serve their needs.

Another cool thing for me about Circuit Cellar is the magazine’s origin story. Back when I was in high school and in my early days studying Computer Science in college, Steve Ciarcia had a popular column called Circuit Cellar in BYTE magazine. I was a huge fan of BYTE. I would take my issue and bring it to a coffee shop and read it intently. (Mind you this was pre-Internet. Coffee shops didn’t have Wi-Fi.) What I appreciated most about BYTE was that it had far more technical depth than the likes of PC World and PC Computing. I felt like it was aimed at a person with a technical bent like myself. When Steve later went on to found this magazine—nearly 30 years ago—he gave it the Circuit Cellar name but he also maintained that unique level of technical depth that entices engineers.

With all that in mind, I plan to uphold the stature and legacy in the electronics industry that I and all of you have long admired about Circuit Cellar. We will work to continue being the Most Technical information resource for professional engineers, academics, and other electronics specialists world-wide. Meanwhile, you can look forward to expanded coverage of those exciting market-spaces I discussed earlier. Those new applications really exemplify how embedded computing technology is changing the world. Let’s have some fun.

Don’t Miss CC’s Newsletter: IoT Technology Watch

The Internet-of-Things (IoT) phenomenon is rich with opportunity. Circuit Cellar’s IoT Technology Focus themed newsletter is coming to your inbox tomorrow. The newsletter will update you on the latest news and trends including IoT gateways, IoT device security, IoT wireless connectivity and IoT cloud implementations.

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

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

Remember, our new enhanced weekly CC Newsletter will switch its theme each week, so look for these in upcoming weeks:

Embedded Boards. This content looks at embedded board-level computers. The focus here is on modules (e.g., Arduino, Raspberry Pi, COM Express, and other small-form-factor modules) that ease prototyping efforts and let you smoothly scale up production volumes.

Analog & Power. 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. 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.

Circuit Cellar Newsletters to Focus on Microcontrollers, IoT and More

Circuit Cellar’s ongoing mission is to provide important information to help you make smart choices with your engineering projects—from prototype to production. As part of that effort, we’re now offering themed newsletter content each week that focuses on critical areas of system development.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get the first “Microcontroller Watch” themed newsletter issue tomorrow.

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

Our new enhanced weekly CC Newsletter will switch its theme each week, covering these four areas every month:

Microcontroller Watch. 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. The Internet-of-Things (IoT) phenomenon is rich with opportunity. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Embedded Boards. This content looks at embedded board-level computers. The focus here is on modules (e.g., Arduino, Raspberry Pi, COM Express, and other small-form-factor modules) that ease prototyping efforts and let you smoothly scale up production volumes.

Analog & Power. 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.

Expansion Connector Sample Kits Target Makers

Samtec has announced the release of four unique Expansion Connector Sample Kits for Makers. These new kits allow continued growth and stacking of the most popular electronics platforms using standard 0.100″ (2.54mm) centerline IDC cables, sockets and headers. Rapid prototyping of innovative projects using open-source electronic platforms typically requires basic connectors and cable assemblies.

Samtec RasberryPi3Kit

Samtec has developed Expansion Connector Sample Kits for four of the most popular platforms:

  • Arduino Uno R3 Expansion Connector Sample Kit
  • BeagleBone Black Expansion Connector Sample Kit
  • ARM mbed Application Board Expansion Connector Sample Kit
  • Raspberry Pi 3 Expansion Connector Sample Kit

Samtec | www.samtec.com

BitScope Blade for Raspberry Pi

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

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

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

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

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

Source: element14

Raspberry Pi Maker: An Interview with Eben Upton

About five years ago, a small group of enthusiast designers led by Eben Upton launched a small, inexpensive computer that looked nothing like a normal computer. The bare green PCB board appealed to makers and hackers and the option to connect a keyboard and screen appealed to traditional computer nerds. Today, the Raspberry Pi is the best-selling personal computer in the United Kingdom.

Circuit Cellar recently visited Cambridge, England, to interview Upton about his work at the Raspberry Pi Foundation and more. Check it out.

New Raspberry Pi Model B+

The Raspberry Pi foundation announced what it calls “an evolution” of the Raspberry Pi SBC. Compared to the previous model, the new Raspberry Pi Model B+ has more GPIO, and more USB ports. In addition, it uses Micro SD memory cards and improved power consumption.

Source: Raspberry Pi Foundation

Source: Raspberry Pi Foundation

 

The GPIO header is now 40 pins, with the same pinout for the first 26 pins as the Model B. The B+ also has four USB 2.0 ports (compared to two on the Model B) and better hotplug and overcurrent behavior. In place of the old friction-fit SD card socket is a better push-push micro SD version.

In line with today’s electronic concepts, the new board also lowers power consumption. By replacing linear regulators with switching ones, the power requirements are reduced by between 0.5 W and 1 W. The audio circuit incorporates a dedicated low-noise power supply, enabling better audio applications.

The new board is well organized. The USB connectors are aligned with the board edge, and the composite video now has a 3.5-mm jack. The corners are rounded with four squarely placed mounting holes.

The Raspberry Pi Model B+ uses the same BCM2835 application processor as the Model B. It runs the same software and still has 512-MB RAM.

If you want to adapt a current project to the new platform, be sure to study the new GPIO pins and mechanical specs. To ensure continuity of supply for industrial customers, the Model B will be kept in production for as long as there’s demand for it.

At $35, the new model B+ is the same price as the older model B and is already available from Farnell/element14/Newark and RS/Allied Components.

[Source: www.raspberrypi.org]

Nesit (Meriden, CT, USA)

NESIT wants to create, educate, and foster learning in the fields of various technological and other disciplines. They reap the benefits of productivity through volunteer collaboration.

Location 290 Pratt St., Meriden CT 06450
Members 30
Website nesit.org

Read about what Vice President Will Genovese has to say about NESIT.
Tell us about your meeting space!

NESIT meets in a 4000 square feet office that takes place in The Meriden Enterprise Center. A large office and manufacturing building that is home to over 60 businesses.

What tools do you have in your space? 

Soldering stations, oscilloscope, 3-D printer, woodshop, cnc, and a data center.

Are there any tools your group really wants or needs?

A lasercutter would be a nice addition to our arsenal.

What sort of embedded tech does your Hackerspace work with?

We work with PIC, Arduino, and Raspberry Pi, and many more.
In fact one of our recent projects was a DIY PIC Programmer.

Can you tell us about some of your group’s recent tech projects?

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One of the group’s first tech projects was the “MAME,” a full-size gaming arcade. The project was going well until there was a break in at the location and they lost some equipment; the MAME was put on the backburner.  After they moved to their new location and gained a new member, an art teacher named John, the project garnered interest again. He came up with the design for it. Afterwords it was painted, they got a coin mechanism, speakers were hooked up, and the software was installed and configured. IT was finally finished.

Click here if you want to check it out.

What’s the craziest project you’ve completed?

At the moment we have not yet completed projects I would categorize as “crazy.”

Read more about NESIT on their website. 

Show us your hackerspace! Tell us about your group! Where does your group design, hack, create, program, debug, and innovate? Do you work in a 20′ × 20′ space in an old warehouse? Do you share a small space in a university lab? Do you meet at a local coffee shop or bar? What sort of electronics projects do you work on? Submit your hackerspace and we might feature you on our website!

Linux System Configuration (Part 1)

In Circuit Cellar’s June issue, Bob Japenga, in his Embedded in Thin Slices column, launches a series of articles on Linux system configuration. Part 1 of the series focuses on configuring the Linux kernel. “Linux kernels have hundreds of parameters you can configure for your specific application,” he says.

Linux system configurationPart 1 is meant to help designers of embedded systems plan ahead. “Many of the options I discuss cost little in terms of memory and real-time usage,” Japenga says in Part 1. “This article will examine the kinds of features that can be configured to help you think about these things during your system design. At a minimum, it is important for you to know what features you have configured if you are using an off-the-shelf Linux kernel or a Linux kernel from a reference design. Of course, as always, I’ll examine this only in thin slices.”

In the following excerpt from Part 1, Japenga explains why it’s important to be able to configure the kernel. (You can read the full article in the June issue, available online for single-issue purchase or membership download.)

Why Configure the Kernel?
Certainly if you are designing a board from scratch you will need to know how to configure and build the Linux kernel. However, most of us don’t build a system from scratch. If we are building our own board, we still use some sort of reference design provided by the microprocessor manufacturer. My company thinks these are awesome. The reference designs usually come with a prebuilt kernel and file system.

Even if you use a reference design, you almost always change something. You use different memory chips, physical layers (PHY), or real-time clocks (RTCs). In those cases, you need to configure the kernel to add support for these hardware devices. If you are fortunate enough to use the same hardware, the reference design’s kernel may have unnecessary features and you are trying to reduce the memory footprint (which is needed not just because of your on-board memory but also because of the over-the-air costs of updating, as I mentioned in the introduction). Or, the reference design’s kernel may not have all of the software features you want.

For example, imagine you are using an off-the-shelf Linux board (e.g., a Raspberry Pi or BeagleBoard.org’s BeagleBone). It comes with everything you need, right? Not necessarily. As with the reference design, it may use too many resources and you want to trim it, or it may not have some features you want. So, whether you are using a reference design or an off-the-shelf single-board computer (SBC), you need to be able to configure the kernel.

Linux Kernel Configuration
Many things about the Linux kernel can be tweaked in real time. (This is the subject of a future article series.) However, some options (e.g., handling Sleep mode and support for new hardware) require a separate compilation and kernel build. The Linux kernel is written in the C programming language, which supports code that can be conditionally compiled into the software through what is called a preprocessor #define

A #define is associated with each configurable feature. Configuring the kernel involves selecting the features you want with the associated #define, recompiling, and rebuilding the kernel.

Okay, I said I wasn’t going to tell you how to configure the Linux kernel, but here is a thin slice: One file contains all the #defines. Certainly, one could edit that file. But the classic way is to invoke menuconfig. Generally you would use the make ARCH=arm menuconfig command to identify the specific architecture.

There are other ways to configure the kernel—such as xconfig (QT based), gconfig (GTK+ based), and nconfig (ncurses based)—that are graphical and purport to be a little more user-friendly. We have not found anything unfriendly with using the classical method. In fact, since it is terminal-based, it works well when we remotely log in to the device.

Photo 1—This opening screen includes well-grouped options for easy menu navigation.

Photo 1—This opening screen includes well-grouped options for easy menu navigation.

Photo 1 shows the opening screen for one of our configurations. The options are reasonably well grouped to enable you to navigate the menus. Most importantly, the mutual dependencies of the #defines are built into the tool. Thus if you choose a feature that requires another to be enabled, that feature will also automatically be selected.

In addition to the out-of-the-box version, you can easily tailor all the configuration tools if you are adding your own drivers or drivers you obtain from a chip supplier. This means you can create your own unique menus and help system. It is so simple that I will leave it to you to find out how to do this. The structure is defined as Kconfig, for kernel configuration.

HackRVA (Richmond, VA, USA)

HackRVA Sign4HackRVA is a Richmond-based makerspace. They like to take things apart, put them back together, figure out how they work, and create new things. Their mission? To learn and make stuff sharing tools and knowledge in technology; including Arduino, Makerbot, Linux, and the Open Source movement.

Aaron Nipper will tell us a little more.

Location 1600 Roseneath Road, Suite E, Richmond, VA 23230
Members 65
Website www.hackrva.org

What’s your meeting space like? 

Our space is about 2,000 square feet. We have an AV and general meeting area, a tech lab, and a fab lab.

What’s in your “toolbox”?

  • Two 3D printers
  • Laser cutter
  • Lots of soldering stations
  • O-scopes
  • Hand and power tools
  • A computer lab

Are there any tools your group really wants or needs?

A CNC Router — like a shopbot. Can’t wait to build that first wiki-house!

Arduino, Raspberry Pi, embedded security… which embedded technologies does your group work with most frequently? 

We use all that stuff. Arduino, R-Pi, whatever we can get our hands on! We’ve designed, from scratch, PCB Badges for RichSec security conference the last three years. Click here to learn more about the PCB Badges project.

What have you been working on lately?

For the past three years, we’ve designed those PCB badges for the RichSec security conference. Here’s another recent build where a member took a Power Wheels and made it Xbox controller driven. Check out the video below or click here to read more about that project.

Do you have any events or initiatives you’d like to tell us about? Where can we learn more about them?

You can learn more about us at hackrva.org. We host the Richmond Maker Guild, have regular Saturday Hackathons, as well as a Noise Night. Members are always coming up with creative events!

Any words of advice for fellow hackers?

My personal motto is fail often, teach others, and post to the web. All those things help me learn and think about projects better.

Want to know more about what HackRVA does? Check out their Facebook page and website.

Show us your hackerspace! Tell us about your group! Where does your group design, hack, create, program, debug, and innovate? Do you work in a 20′ × 20′ space in an old warehouse? Do you share a small space in a university lab? Do you meet a local coffee shop or bar? What sort of electronics projects do you work on? Submit your hackerspace and we might feature you on our website!

Build an Automated Vehicle Locator

Several things inspired Electrical and Computer Engineering Professor Chris Coulston and his team at Penn State Erie, The Behrend College, to create an online vehicle-tracking system. Mainly, the team wanted to increase ridership on a shuttle bus the local transit authority provided to serve the expanding campus. Not enough students were “on board,” in part because it was difficult to know when the bus would be arriving at each stop.

So Coulston’s team created a system in which a mobile GPS tracker on the bus communicates its location over a radio link to a base station. Students, professors, or anyone else carrying a smartphone can call up the bus tracker web page, find out the bus’ current location, and receive reliable estimates of the bus’ arrival time at each of its stops. Coulston, computer engineering student Daniel Hankewycz, and computer science student Austin Kelleher wrote an article about the system, which appears in our June issue.

Circuit Cellar recently asked Coulston if the system, implemented in the fall 2013 semester, had accomplished its goals and might be expanded.

“The bus tracker team is tracking usage of the web site using Google Analytics,” Coulston said. “The data reveals that we get on average 100 hits a day during cold weather and fewer on warmer days. Ridership has increased during this past year, helping assure the long-term presence of the shuttle on our campus.”

“Over winter break, shuttle service was increased to a distant location on campus,” he added. “In order to better track the location of the shuttle, a second base station was added. The additional base station required a significant rework of the software architecture. The result is that the software is more modular and can accept an arbitrary number of base stations. There are no plans at present to add a second bus—a good thing, because this change would require another significant rework of the software architecture.”

Initially, Coulston looked to other real-time vehicle trackers for inspiration: “There are a variety of live bus trackers that motivated my early ideas, including the University of Utah’s Live Tracker  and the Chicago Transit Authority’s CTA Bus Tracker. Given our single bus route on campus, I was motivated to keep the interface simple and clean to minimize the amount of time needed to figure out where the bus is and how long it’s going to take to get to my stop.”

The system, as it was originally implemented in August 2013, is fully described in the June issue, now available for single-issue purchase or membership download. The following article excerpt provides a broad overview and a description of the team’s hardware choices.

THE BIG PICTURE
Figure 1 shows the bus tracker’s hardware, which consists of three components: the user’s smartphone, the base station placed at a fixed location on campus, and the mobile tracker that rides around on the bus.

The bus tracking system includes a Digi International XTend radio, a Microchip Technology PIC18F26K22 microcontroller, and a Raspberry Pi single-board computer.

Figure 1: The bus tracking system includes a Digi International XTend radio, a Microchip Technology PIC18F26K22 microcontroller, and a Raspberry Pi single-board computer.

Early on, we decided against a cellular-based solution (think cell phone) as the mobile tracker. While this concept would have benefited from wide-ranging cellular coverage, it would have incurred monthly cellar network access fees. Figure 1 shows the final concept, which utilizes a 900-MHz radio link between the mobile tracker and the base station.

Figure 2 shows the software architecture running on the hardware from Figure 1. When the user’s smartphone loads the bus tracker webpage, the JavaScript on the page instructs the user’s web browser to use the Google Maps JavaScript API to load the campus map. The smartphone also makes an XMLHttpRequests request for a file on the server (stamp.txt) containing the bus’ current location and breadcrumb index.

Figure 2: The bus tracker’s software architecture includes a GPS, the mobile tracker, a smartphone, and the base station.

Figure 2: The bus tracker’s software architecture includes a GPS, the mobile tracker, a smartphone, and the base station.

This information along with data about the bus stops is used to position the bus icon on the map, determine the bus’ next stop, and predict the bus’ arrival time at each of the seven bus stops. The bus’ location contained in stamp.txt is generated by a GPS receiver (EM-408) in the form of an NMEA string. This string is sent to a microcontroller and then parsed. When the microcontroller receives a request for the bus’ location, it formats a message and sends it over the 900-MHz radio link. The base station compares the bus position against a canonical tour of campus (breadcrumb) and writes the best match to stamp.txt.

Early in the project development, we decided to collect the bus’ position and heading information at 2-s intervals during the bus’ campus tour. This collection of strings is called “breadcrumbs” because, like the breadcrumbs dropped by Hansel and Gretel in the eponymously named story, we hope they will help us find our way around campus. Figure 3 shows a set of breadcrumbs (b1 through b10), which were collected as the bus traveled out and back along the same road.

Figure 3: Breadcrumbs (b1 through b10) containing the bus’ position and orientation information were taken every 2 s during a test-run campus tour.

Figure 3: Breadcrumbs (b1 through b10) containing the bus’ position and orientation information were taken every 2 s during a test-run campus tour.

The decision to collect breadcrumbs proved fortuitous as they serve an important role in each of the three hardware components shown in Figure 1.

MOBILE TRACKER
The bus houses the mobile tracker (see Photo 1). Figure 4 shows the schematic, which is deceptively simple. What you see is the third iteration of the mobile tracker hardware.

Figure 4: The mobile tracker includes a Microchip Technology PIC18F26K22 microcontroller, a Micrel MIC5205 regulator, a Digi International XTend RF module, and a Texas Instruments TXS0102 bidirectional translator

Figure 4: The mobile tracker includes a Microchip Technology PIC18F26K22 microcontroller, a Micrel MIC5205 regulator, a Digi International XTend RF module, and a Texas Instruments TXS0102 bidirectional translator

An important starting point in the design was how to step down the bus’ 12-V supply to the 5-V required by our circuit. In terms of hardware, the best decision we made was to abandon the idea of trying to integrate a 12-to-5-V converter onto the mobile tracker PCB. Instead we purchased a $40 CUI VYB15W-T DC-DC converter and fed the mobile tracker 5-V inputs…

We used Micrel’s MIC5205 regulator to step down the 5 V for the 3.3-V GPS receiver, which easily supplied its peak 80 mA. Since we ran a Digi International XTend radio at 5 V for the best range, we ended up with mixed voltage signals. We used a Texas Instruments TXS0102 bidirectional voltage-level translator, which handles voltage-interfacing duties between the 5-V radio and the 3.3-V microcontroller.

The mobile tracker unit

Photo 1: The mobile tracker unit

We selected Microchip Technology’s PIC18F26K22 because it has two hardware serial ports, enabling it to simultaneously communicate with the GPS module and the radio modem when the bus is traveling around campus. We placed two switches in front of the serial ports. One switch toggles between the GPS module and the Microchip Technology PICkit 3 programming pins, which are necessary to program the microcontroller. The second switch toggles between the radio and a header connected to a PC serial port (via a Future Technology Devices FT232 USB-to-serial bridge). This is useful when debugging at your desk. An RGB LED in a compact PLCC4 package provides state information about the mobile tracker.

The XTend RF modules are the big brothers to Digi International’s popular XBee series. These radios come with an impressive 1 W of transmitting power over a 900-MHz frequency, enabling ranges up to a mile in our heavily wooded campus environment. The radios use a standard serial interface requiring three connections: TX, RX, and ground. They are simple to set up. You just drop them into the Command mode, set the module’s source and destination addresses, store this configuration in flash memory, and exit. You never have to deal with them again. Any character sent to the radio appears on the destination modem’s RX line.

The GPS receiver utilizes the CSR SiRFstarIII chipset, which is configured to output a recommended minimum specific (RMC) string every 2 s…

The mobile tracker’s firmware listens for commands over the serial port and generates appropriate replies. Commands are issued by the developer or by the base station…

Burning breadcrumbs into the mobile tracker’s flash memory proved to be a good design decision. With this capability, the mobile tracker can generate a simulated tour of campus while sitting on the lab bench.

BASE STATION
The base station consists of an XTend RF module connected to a Raspberry Pi’s serial port (see Photo 2). The software running on the Raspberry Pi does everything from running an Nginx open-source web server to making requests for data from the mobile tracker.

From Figure 1, the only additional hardware associated with the base station is the 900-MHz XTend radio connected to the Raspberry Pi over a dedicated serial port on pins 8 (TX) and 10 (RX) of the Raspberry Pi’s GPIO header.

The only code that runs on the base station is the Python program, which periodically queries the mobile tracker to get the bus’ position and heading. The program starts by configuring the serial port in the common 9600,8,N,1 mode. Next, the program is put into an infinite loop to query the mobile tracker’s position every 2 s.

Photo 2: The base station includes an interface board, a Raspberry Pi, and a radio modem.

Photo 2: The base station includes an interface board, a Raspberry Pi, and a radio modem.