The beacon designer needs to consider:
- battery life;
- security and privacy; (next post)
- the vendor.
1. Hardware Building Blocks
A self-contained beacon product can be implemented with a wireless System-on-Chip (SoC) or a module, along with a battery and a mechanical enclosure. But it will likely include other components such as pushbuttons, LEDs, piezo buzzers, sensors, and reed switches.
A pre-certified module with all these features provides the fastest time to market, while a discrete SoC design might provide size or cost savings over the long run.
The whitepaper Six Hidden Costs in a 99 Cent SoC provides a good discussion of the financial and developmental trade-offs for using a module or SoC.
Typical pre-certified Bluetooth low energy beaconing module and Bluetooth SoC reference design
It’s fundamentally important to choose a widely deployed and field-proven Bluetooth stack. Most often, this market success is more important than any promises of new cutting edge features. Market success indicates good customer support and a stable stack, both of which help get to market quickly.
For beacons in particular, it’s very important that the protocol efficiently manages sleep modes. A beacon typically broadcasts it advertising packets for about 1% of its life. The vast majority of the remaining 99% are spent in deep sleep mode. Having a proven, energy efficient stack is obviously very important for both states.
Beacon Application Code
Writing the beacon code can also be very simple if the developer uses a proven Bluetooth programming tool. Silicon Labs’ BGScript is a very mature software abstraction tool. It is a simple, high-level, BASIC-like programming language that allows developers to quickly develop their Bluetooth applications.
This BGScript example code for the BGM111 shows a functional iBeacon implementation. It takes just 38 lines, most of it comments. While this is a very simple example, its power and simplicity are obvious.
BGScript iBeacon example code for the BGM111 Bluetooth low energy module
3. Battery Life
As with any product, a beacon’s battery capacity versus power consumption determine its operating life.
The beacon’s transmit power and beaconing interval play an important role here. But there are trade-offs to be made.
- Long transmit range takes more battery life (high transmit power), but provides more coverage area.
- Short transmit range limits coverage, but may be suitable for close-proximity applications.
- Short beaconing intervals allow for better location approximation through more data points.
- Long beaconing intervals conserve battery life, but may be missed by scanners entirely.
A beacon’s average battery life is determined by transmit power and its transmit / sleep duty cycle
Current profile in a typical Bluetooth low energy advertising event (ADV PDU)
Whitepaper on Developing with Bluetooth BLE Beacons
Our experts have put some very relevant information in a whitepaper on developing with Bluetooth beacons, which can be downloaded here. The goal is to help you get to market quickly with the right, stable solution.
It covers a lot of territory:
- We examine beacon applications to help you brainstorm some of your own.
- We provide a short history of Bluetooth and its derivatives, including Bluetooth