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Inside a Beacon – Part 2 – The System on a Chip (SoC)

This is part 2 of a 3 part series that explains what’s inside a beacon. In this part we take a look at the System on a Chip (SoC), in particular the Nordic nRF range, found in many beacons.

In part 1 we identified the Nordic nRF52832 SoC. The nRF52 is a newer version of the Nordic nRF51 that has been used in millions of beacons. The new version has more memory, uses less power and includes NFC. The extra memory is useful for applications such as Bluetooth Mesh.

The Nordic nRF52832 SoC wasn’t created just for beacons. It’s a general purpose device for any electronics that needs to have 2.4GHz wireless communications and software processing. The nRF51 and nRF52 series can be found in many fitness trackers and wearables. For example, the BBC micro:bit, the Polar GPS multisport watch and Garmin’s child activity monitor.

The SoC is a stand alone computer having an ARM® Cortex™-M4 CPU with a floating point unit. The NFC-A Tag can be used in pairing and payment solutions which makes it suited for use with smartphone apps. The SoC also has digital peripherals and interfaces such as PDM and I2S for digital microphones and audio.

It has very low power consumption via an on-chip adaptive power management system. It uses between 0.3 μA and 1.9 μA, depending on the mode, and can still respond to events. For beacons, it periodically wakes up for about 1ms, during which it uses about 5.3 mA (at 0 dBm power output).

The SoC supports ANT™, IEEE 802.15.4, Thread, and proprietary protocols operating in the 2.4 GHz bandwidth as well as Bluetooth®.

The marking on the chip denotes the variant with different RAM and flash combinations:

nRF52832-QFAA 64 kB 512 kB
nRF52832-QFAB 32 kB 256 kB
nRF52832-CIAA 64 kB 512 kB

The image in part 1 shows the i7 beacon has the QFAA variant with 64 kB RAM 512 kB Flash. As with SSDs, the flash can only be erased and written so many times. For the nRF52832 this is 10,000 erase/write cycles. This is irrelevant for most beacons as they save very little data, irregularly, usually only when settings are changed. However, for applications such as mesh, the number of erase/write cycles needs to be minimised to prevent the device wearing out in a short period of time.

Part 3

Inside a Beacon – Part 1 – The Physical Beacon

This is part 1 of a 3 part series that explains what’s inside a beacon. In this part we take a look at the physical beacon.

All beacons are similar inside because they are based on standard circuit designs from Nordic Semiconductor, Dialog Semiconductor or Texas Instruments. These semiconductor manufacturers produce a complete system on a chip (SoC) that requires minimal external components. The SoC is a small computer with memory that runs software created by the manufacturer of the beacon. We will take a deeper look at the SoC in part 2 and the software in part 3.

For this series of articles we going to take a deeper look at Minew’s i7 beacon. It’s based on Nordic Semiconductor’s nRF52832 SoC.

Inside the case is a PCB with a CR2477 slide in battery at the rear.

The main chip you can see is the mRF52832. At the top you can also see the antenna that’s created using a track in the printed circuit board. The holes at the bottom right are connections used to program the beacon.

To understand more, we need to look at the printed circuit board design and circuit schematic:

Circuit diagram – **click to see larger in new window**

It can be seen that there aren’t many external components. Y1, the metal component at the top is the crystal used to maintain timing. The SoC has a number of programmable input/output (PIO) pins that are multi-purpose. In a beacon some are usually connected to LEDs and a switch as shown at the left hand side of the circuit diagram. There are also capacitors that need to be external to the SoC.

U2, U3 and U4 are optional for this beacon and missing from this variant of the i7. U2 is the KX022-1020 accelerometer. U3 is the SHT31 temperature/humidity sensor. U4 is the BH1721 light sensor.

In part 2 we take a closer look at the nRF52 SoC.

Latest Nordic WirelessQ Magazine Available

Beacons are small computers with a complete System on a Chip (SoC). There are four main companies that manufacturer SoCs: TI, Dialog, NXP and Nordic. Nordic is the most popular SoC for use in beacons, mainly because of the lower (tool) license cost and ease for beacon manufacturers developing the software (actually called firmware) that runs in the beacons.

Nordic has a new free Wireless Quarter Magazine that showcases uses of Nordic SoCs in many types of device, not just beacons.

Learn about:

Gartner research showing sensor innovation fosters IoT growth
Beacons help U.S. shoppers find way
Bluetooth LE in Amazon FreeRTOS
Bluetooth LE smart textiles on the rise
Article combining Bluetooth Low Energy and LPWANs
Firmwave’s use of Bluetooth Low Energy beacons to build an inexpensive satellite broadcast system
Article on Getting started with Bluetooth mesh

Testing if a Beacon is Working

It’s often the case you need to know if a beacon is working and advertising the correct information. It’s also sometimes necessary to differentiate between beacons, based on their signal strength, so you know you are setting up the correct beacon. Other times, you might want to know a beacon’s MAC address.

The best scanning app is Nordic nRF Connect that’s written by the manufacturer of the System on a Chip (SoC) in most beacons. Nordic nRF Connect detects all beacons and indeed all Bluetooth LE devices, irrespective of the SoC manufacturer because it just looks for standard Bluetooth advertising. nRF Connect is intelligent in that it works out the kind of beacon and displays the appropriate type of information.

It’s important you use the Android version of nRF Connect. Due to over-zealous efforts by Apple to hide identities, it’s not possible for iOS scanning applications to see advertising iBeacon (UUID, major and minor) information nor the Bluetooth MAC address.

Here’s an example scan:

In the above screenshot you can an iBeacon that has been tapped on to show extra information. All devices have the MAC address and a Received Signal Strength Indicator (RSSI). The MAC address uniquely identifies the device.

Devices that scan for beacons will experience a signal strength (RSSI) that varies depending on the distance to the beacon. It’s expressed in dBm and is always negative. A more negative number indicates the beacon is further away. A typical value of -10 to -30 dBm indicates the beacon is close. A typical value of -110 indicates the beacon is near the limit of detection. You can use this to determine which beacons are closest. You usually configure beacons when they are right next to the phone and have a higher, less negative, RSSI.

nRF Connect also shows the advertising period that’s based on how often the app sees the advertising as opposed to what has been set in the beacon. The value is rarely exactly what you have set because Bluetooth requires some randomisation of the advertising period to reduce the possiblity of collisions between devices, in the vicinity, that are set to the same period. Also, being wireless, not all advertising is seen which causes jumps in the shown advertising period. Read more about choosing the advertising period.

There’s also a ‘RSSI at 1m’ which is the beacon’s self-declared value, in the advertising data, of what the RSSI should be at 1m. This can be used by scanning devices, such as apps, as a form of calibration for determining distance. In most cases this value isn’t used and should be ignored. Read more about power and the measured power calibration value.

New Waterproof S1 Sensor Beacon in Stock

We have the new Minew S1 in stock. It’s a sensor beacon with accelerometer, temperature and humidity as well as iBeacon/Eddystone. Unusually for a temperature/humidity beacon it is waterproof to IP65 making it suitable for use outdoors. Sensor beacons like this usually have the sensor on the PCB and a hole in the case to pass through ambient temperature and humidity. Instead, the sensor is outside the beacon:

This beacon takes 2 AAA batteries and uses a newer, more efficient Nordic nRF52 System on a Chip (SoC) for a long 3 year battery life.

Standard vs Proprietary Technology

There’s a thought provoking article, by Lorenzo Amicucci, on the Nordic Semiconductor blog on End-User Factors Impacting Industrial IoT Connectivity. Nordic is the manufacturer of the System-on-a Chip (SoC) in most beacons and Lorenzo is one of their Business Development Managers. While the article talks about Industrial IoT Connectivity and by implication Bluetooth Mesh, the insights are applicable to any project that has to choose between standard or proprietary technology.

The main conclusion is that the best solution from a technical perspective is not always best for the customer. Instead, the best solution should depend on the longer-term business strategy. While a proprietary technology can have the advantage of differentiating your offering it can suffer from future limited supplier availability and possibly shorter lifetime of the technology. Large rollouts:

“…want the confidence that a huge capital spend won’t be wasted on a technology that will be left obsolete in a couple of years.”

More specfically, new and second sourced products from other vendors need to guarantee interoperability for the lifetime of your project.

Read about Generic Beacons

Nordic nRF5 SDK for Mesh v2.0.0 Released

Nordic, who provide the System on a Chip (SoC) in many beacons, have released v2 of their Mesh SDK that implements standard Bluetooth Mesh.

The main improvements are around support for Bluetooth GATT. It’s now possible for devices such as commercial beacons or smartphones to participate in the mesh via the GATT Proxy mechanism. It’s also possible for devices such as smartphones to provision new devices via GATT through Provisioning Bearer GATT (PB_GATT) rather than via firmware API or the serial API. Unfortunately, there are currently no app examples so there’s a large learning curve and development mountain to overcome to implement products based on these mechanisms.

Martin Woolley, who works for the Bluetooth organisation as an evangelist, has new slides (PDF – needs login at Google for some reason) from a Bluetooth Mesh talk at DroidConIT. The slides explain many of the mesh concepts. Here’s the slide showing the GATT proxy mechanism:

The documentation for Mesh v2 is on the Nordic web site.

Diversity in Uses of Beacons

The latest Spring 2018 WirelessQ Magazine (pdf) from Nordic demonstrates some diverse uses of beacons. For example, it mentions the use of Beacons to open doors for the visually-impaired:

A later article in the magazine explains how Bluetooth Low Energy is rapidly
expanding into industrial markets:

“Bluetooth LE technology is growing far beyond its consumer roots by underpinning innovative solutions for the Industrial Internet of Things”

Bluetooth 5 Simultaneous Multiple PHY

If you have been following our posts on Bluetooth 5, you might be wondering how one Bluetooth device can communicate to many devices, some of which might be legancy Bluetooth 4.

There’s a new video from Nordic Semiconductor (who produce the System on a Chip – SoC – inside most beacons) where the new long range mode is used while connecting to up to 20 devices. These can be different PHYs meaning that different capabilities, for example high speed vs long range vs legacy) can be connected at the same time.

Latest Nordic Wireless Quarter Magazine Available

Nordic has a new free Wireless Quarter Magazine that showcases uses of Nordic SoCs in many types of device, not just beacons.

The magazine also has articles on how Nordic is the first to launch a Bluetooth mesh Software Development Kit, how Mesh strengthens Bluetooth wireless’ IoT credentials and explains Bluetooth 5’s advertising extensions. The article says of Bluetooth 5’s advertising extensions:

“Advertising extensions, periodic advertisements, and connectionless broadcast will have a major impact on beacons”

However, the article says:

“This won’t happen overnight because few current smartphones incorporate Bluetooth 5, but expect beacons to proliferate over the next several years as new smartphones are rolled out”