Tag – You’re It: Location-Based Solutions Leveraging Bluetooth Smart for Low-Cost Tagging

By Dave Bursky

Contributed By Electronic Products

Whether it is a laptop, tablet, smartphone, or some other device, many of us have experienced the potential or actual loss of a device by leaving it behind at a coffee shop, the airport, a taxi, or some other location. However, with the availability of Bluetooth-based smart tags and other types of geofencing devices such as the Apple iBeacon, there are many options to prevent the loss of a device that may contain irreplaceable data or data you do not want to hackers to get — contacts, personal data, photos, business plans, and more. These tags combine Bluetooth hardware and software apps that run on smartphones or tablets, and can warn you when you step away from a tagged device. Through the software app running on the phone or tablet, the range can be adjusted from several feet to about 30 feet, and the other features can be activated or disabled.

The Apple iBeacon is a relatively new application that extends Location Services in the Apple iOS operating system. Location Services allow location-based applications and websites (including maps, cameras, Safari, and other Apple and third-party apps) to use information from available cellular, Wi-Fi, Global Positioning System (GPS) networks, and iBeacons to determine your approximate location.

For example, using Wi-Fi or GPS or a cellular connection, an application could use your location data and perform a location search query to find nearby coffee shops, gas stations, or theaters; or your device could set its time zone automatically based on the device’s current location. The application software requires that you enable Location Services on your device and give your permission to each app or website before it can use your location data. In iOS 7, if you turn off Location Services and use Find My iPhone Lost Mode, Location Services will be re-enabled on the device as long as the device is in Lost Mode. Once Lost Mode is disabled, Location Services will return to its previous state.

Basically, tags are low-cost devices that combine a Bluetooth 4.0 transceiver (typically using the Bluetooth low energy portion of the 4.0 standard), possibly a low-end microcontroller (potentially embedded in the Bluetooth transceiver chip) or a standalone MCU, a coin-cell battery, an annunciator and an LED indicator. The latest Bluetooth specification uses a service-based architecture based on the attribute protocol (ATT). All communication in low energy takes place over the Generic Attribute Profile (GATT), which is used when implementing the Bluetooth Smart interface. An application or another profile uses the GATT profile so a client and server can interact in a structured way.

As part of the Bluetooth 4.0 standard, Bluetooth Smart brings three essential features to the beacon experience: an intelligent wireless connection that can authenticate and manage interactions; an extremely power-efficient connection that does not drain the user’s phone battery; and ubiquitous support from phone manufacturers and mobile operating systems.

Implementing iBeacon

Apple iBeacons and other location-based sensors can be implemented as tags and “attached” to products or people, then linked to a smartphone or tablet. The tags have a range between 100 and 150 feet in line-of-sight applications. Companies offering Bluetooth Smart chips and subsystems include CSR, Nordic Semiconductor, NXP Semiconductors, STMicroelectronics, Texas Instruments, and others.

A typical beacon reference design offered by Nordic Semiconductor consists of their highly-integrated BLE transceiver chip, the nRF51822, a 2.4 GHz antenna, and contacts pads to connect a sensor or other function – all on a board just 20 mm in diameter (Figure1). Inside the nRF51822 chip is a 32-bit ARM Cortex-M0 CPU with 256 Kbytes of Flash and 16 Kbytes of RAM, thus eliminating the need for a separate microcontroller. The reference design includes ten general-purpose I/O pins, two buttons that are used to switch operating modes, one RGB LED indicator, and is fully programmable via an SPI port and supports over-the-air firmware updates. The nRF51822 Bluetooth Smart Beacon Kit includes one beacon and full access to software and design files.

Image of nRF51822 from Nordic Semiconductor

Figure 1: This simple reference design, the nRF51822 from Nordic Semiconductor allows designers to craft Apple iBeacon-compatible applications using the company’s highly-integrated transceiver chip that incorporates a low-power microcontroller.

Similar to the Nordic chip, the CSR1011 from Cambridge Scientific Research (CSR) keeps the component count very low by also integrating a 16-bit RISC-based microcontroller, 64 Kbytes of system RAM, 64 Kbytes of internal ROM, and the full Bluetooth Low Energy transceiver (Figure 2). In its dormant mode, the chip consumes less than 600 nA, thus allowing a coin cell to power the chip for a year or more if the chip is activated a few times per day. The on-chip MCU provides designers with resources such as a 10-bit A/D converter, 32 digital I/O lines, three analog I/O pins, a UART, an I²C/SPI port, four pulse-width-modulated timer modules, and even a switch-mode power supply controller.

Image of CSR1011 Bluetooth Low Energy transceiver chip from CSR

Figure 2: A highly-integrated Bluetooth Low Energy transceiver chip, the CSR1011 developed by CSR, only implements the low energy portion of the Bluetooth 4.0 standard and is a complete system-on-chip solution for designs that require minimal component count.

When an iBeacon device is linked to an iOS device, the beacon can alert apps when you approach or leave a location with an iBeacon. In addition to monitoring location, an app can estimate your proximity to an iBeacon (for example, a display or checkout counter in a retail store). Depending on your device and available services, Location Services uses a combination of cellular, Wi-Fi, Bluetooth, and GPS to determine your location. If you are not within a clear line of sight to GPS satellites, your device can determine your location using crowd-sourced Wi-Fi and cell tower locations or iBeacons.

Apps that can show your location on the screen, including Maps, indicate your current (approximate) location using a blue marker. If your location cannot be determined precisely, a blue circle also appears around the marker. The size of the circle shows how precisely your location can be determined—the smaller the circle, the greater the precision.

A typical Bluetooth 4.0 tag might be about the size of a quarter and perhaps about three times as thick. One example of such a tag is the StickR TrackR device offered by Phone-Halo (Figure 3). The tag, with a diameter of about one inch, is small enough to attach to a key ring or using double-sided tape, stick to a notebook or tablet, or even attach to a dog collar. In addition to the disk-shaped tag, the company also has a thin wallet-sized rectangular device that is 4 cm wide by 6.5 cm long and just 0.4 cm thick. It uses two CR2016 coin cells and can last for about two years.

The software application that runs on the iOS or Android phone or tablet allows the user to view the distance between the phone/tablet and the tagged item, with the tap of finger on the application, the tag will ring, thus indicating its location, and the software allows the StickR to be fully customized for sound-alert settings, range, and other features. The tag on the keychain or attached to another device also works in reverse – it has a button that, when pressed, will cause your iOS or Android device to ring, thus allowing you to find the misplaced phone or tablet.

Image of small Bluetooth 4.0 tag developed by Phone-halo

Figure 3: The small Bluetooth 4.0 tag developed by Phone-halo can operate for over a year from a single CR2016 coin cell. The software application running on an iOS or Android device can keep tabs on five to ten tagged items simultaneously.

In summary, the advent of Bluetooth Low Energy devices has opened a new application area that includes iBeacons, tags, and many other solutions that leverage its low standby power and smartphone technologies to provide both loss prevention and new location-based services. As the BTLE devices get more highly integrated, costs will continue to drop and that will continue to open additional market opportunities.

For more information on the parts discussed in this article, use the links provided to access product information pages on the Digi-Key website.

Disclaimer: The opinions, beliefs, and viewpoints expressed by the various authors and/or forum participants on this website do not necessarily reflect the opinions, beliefs, and viewpoints of Digi-Key Electronics or official policies of Digi-Key Electronics.

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Dave Bursky

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Electronic Products

Electronic Products magazine and ElectronicProducts.com serves engineers and engineering managers responsible for designing electronic equipment and systems.