As it is for everything Google or Android, Eddystone is an open source protocol specification by Google released in July 2015, which defines Bluetooth Low Energy message format specifically for Beacons. Unlike iBeacon, which is officially supported by iOS devices only, Eddystone has official support for both iOS and Android.
To read and explore the Eddystone specification, visit https://github.com/google/eddystone.
The Eddystone protocol format has been named after the famous Eddystone lighthouse in the UK and defines four different message formats as shown as follows:
Figure 4: Eddystone Beacon Format (Source: developer.mbed.org)
We shall cover each message format in detail:
- Eddystone-UID: Eddystone-UID is used to broadcast a 16-byte Beacon identifier. The 16-byte Beacon identifier is divided into two parts, namely, namespace (10 bytes) and instance (6 bytes). A namespace is something that differentiates similar kind of Beacons from other Beacons (something like, "Since this beacon has that namespace hence it belongs to a Popular Fast food Chain"). For the sake of understanding, let's say a popular fast food chain has 5 different outlets in a huge retail shopping mall. Each outlet has 2 beacons, one near the burger counter and 1 near the milk shake counter making it a collective of 10 beacons. Then all of those 10 Beacons will have a similar namespace ID, since they all belong to a similar context(same fast food company). However, each of those 10 Beacons will have different instance ID (something like, "Since this beacon has that Namespace hence it belongs to a Popular Fast food Chain and since it has this Instance ID hence it belongs to that shop near the Milkshake Counter. For the burgers, there is a separate beacon placed near the Burger Counter."), so as to identify each of them uniquely as shown in the following figure:
Figure 5: Namespace and Instance in Eddystone UUID format
- Eddystone-URL: The EddyStone-URL packet consists of a single URL field used to broadcast a URL, as shown previously in the figure indicating the beacon format, which can then navigate the user to any website that has SSL security. These URLs form the backbone of something known as Physical Web, a platform using which Google plans to convert Internet of things to Internet of any thing.
To read more about Physical Web, visit http://google.github.io/physical-web/.
- Eddystone-TLM: Eddystone-TLM packet broadcasts telemetry information about the Beacon itself. The telemetry packet consists of the following:
- Battery voltage: This can be used to estimate the battery level of a beacon
- Beacon temperature: This is the number of packets sent since the beacon was last powered-up or rebooted
- Beacon uptime: The is the time since last power-up or reboot
- Eddystone-EID: Eddystone-EID is a time varying packet, somewhat similar to the UID packet, however, specifically designed for security against hijacking and spoofing.