This Application Note is intended for anyone interested in understanding the Bluetooth Low Energy (BLE) capabilities supported by Enlighted’s SU-5 sensors and how these capabilities might be used for custom applications.
An Enlighted SU-5E sensor contains a BLE radio capable of receiving or transmitting BLE advertising beacons. The Enlighted Where application uses the sensor network to receive BLE advertising messages from BLE tags to provide Real-Time Location Services (RTLS). There are limitations regarding how the sensor or the Where application can be used for custom applications.
BLE Receive Mode
By default, the BLE radio is turned off when a sensor is commissioned. You can enable the BLE functionality in either Receive or Transmit (Beacon) mode in Manage. Refer to the article Set Bluetooth (BLE) Mode. When a sensor is set in Receive mode, the sensor can only receive BLE messages that conform to Enlighted’s manufacturer-specific advertising format. Tags, such as Badge and Asset tags that support Enlighted’s advertising format, also contain an accelerometer that will change the tag's advertising interval based on the tag's movement.
Enlighted’s Where application uses sensor location, tag information, and Received Signal Strength (RSSI) of the tag to locate the tag on the building floor plan. The Where application does not provide location services for tags, not advertising the Enlighted format.
Currently, there is no API that provides access to the raw BLE advertising messages received by the sensor. Therefore, an Enlighted sensor network cannot be used to support 3rd-party RTLS applications, irrespective of whether Enlighted tags or 3rd party tags generate the BLE messages.
When a sensor is set to Transmit (beacon) mode, the sensor will transmit BLE advertising messages in the iBeacon format every 500 msecs at 0dBm. Any device capable of understanding iBeacon messages and within the sensor's range can receive and process the sensor’s advertisements.
The specifics of the iBeacon advertisement are as follows:
1. Company ID (Apple Company ID): 0x004c
2. Device Type (Standard iBeacon): 0x02
3. Beacon Format Fields:
- UUID (16 bytes): 441651aa-4036-11e6-beb8-9e71128cae77
- Major/Minor Field Information (4 bytes) contains lowest 3 bytes of sensor’s MAC address
Upper 8 bits of Major - always 0
Lower 8 bits of Major – MAC address 
Upper 8 bits of Minor - MAC address 
Lower 8 bits of Minor - MAC address 
- BLE Transmit Power (1 byte).
Note that this message does not contain any user-definable location or geospatial information.
4. BLE TX Power Setting: 0 dBm
5. BLE Beacon Interval: 500ms
6. BLE range depends on surroundings, radio performance, and antennas. Typically, the BLE range should
be 50 feet radius in line of sight.
When a sensor is installed and configured without connection to a fixture, the sensor is called a “fixtureless sensor” and identified as such in Enlighted Manage.
Adding such sensors will increase the sensor density in a facility and improve the accuracy of the Where application. Any improvement to 3rd-party RTLS application accuracy due to additional fixtureless sensors is unknown since the beaconing sensors do not transmit location or geospatial information.