The transmitter is enclosed in a plastic, non waterproof, case of 4x4cm size:
The enclosure has a hole that allows you to hang the iBeacon on the wall or alternatively use it as a key ring.
The transmitter is based on a double-sided circuit board: one side hosts all the components, while on the other side you find the lithium battery that powers the iBeacon. The antenna is also printed directly on the PCB.
A switch allows you to turn the iBeacon on or off:
The use is very simple: just turn the iBeacon on and it continuously transmits the advertising package containing its unique UUID.
The manufacturer also offers an application to customize some parameters of the iBeacon. For iOS smartphones you can download the “Wellcore Beacon Tool” app from the App Store, while for Android the apk file of the application is available for download on this website.
The app performs a scan looking for compatible iBeacons:
Once found an iBeacon, you can change some of its parameters (in the example, its name):
The change is effective as soon as you click the Write command:
In my previous article I explained the Bluetooth Low Energy technology and the advertising process.
You learned that a BLE device can leverage the advertising packets to send data; in this case the device is called broadcaster and the devices which receive data are called observers.
The payload of an advertising packet has the following structure:
ADV ADDR is the device MAC address (this is the address displayed by the program developed in the previous article) and ADV DATA is a field, with a max length of 31 bytes, that contains one or more structures, each with 3 elements:
AD length is the total length (in bytes) of each data structure
AD type is the type of data contained in the structure
A device, for example, can transmit its local name using the AD type 0x09:
In scan mode, the Bluetooth driver returns to the program the received data (ADV DATA) in thescan_result->scan_rst.ble_adv array. This array contains uint8_t values and it’s size is scan_result->scan_rst.adv_data_len.
The Bluedroid library contains a method, esp_ble_resolve_adv_data(), which allows to get the value for a specific AD type passing the raw data. The header file esp_gap_ble_api.h contains definitions for the most common AD types:
In my Github repository you can find an updated version of the scan program. Thanks to what explained above, now the program can also display – if available – the name of the device:
A particular family of broadcaster devices are the iBeacons. These devices have been designed by Apple to allow interaction with IOS devices (iPhone …) based on location awareness. Let’s make an example: an iPhone can “notice” that it is close to a particular iBeacon, associated with a room in a museum, and therefore offer the user a brief guide to the exhibited works.
iBeacon specifications are available on Apple’s developer portal. iBeacons work transmitting advertising packets with specific payload (ADV DATA):
The first structure has AD type = flags (0x01). Each bit has a different meaning, usually iBeacons use 0x0A value for AD data.
The second structure has type = 0xFF, that is Manufacturer Specific Data. The Bluetooth standard allows the different manufacturers to use this ID to transmit custom data. The total data length is 25 bytes (0x1A – 0x01 that is the length of the AD type field).
Apple specifications further subdivide the AD data field in several elements:
The first field is the manufacturer/company; iBeacons normally use the code 0x004C, assigned to Apple Inc. The next two fields define the iBeacon type and have a fixed value (0x02 e 0x15). The UUID field, together with the Major and Minor ones (optional, they can have a value of 0) uniquely identifies each iBeacon. (insieme con i campi Major e Minor (facoltativi, possono essere impostati a 0) identificano univocamente il singolo iBeacon. Finally, the TX power field contains a measurement, one meter away from the iBeacon, of the received power and is useful for precisely estimate the distance between the phone and the iBeacon itself.
I developed a program for the esp32 chip which turns a relay on if it detects a specific iBeacon. Via menuconfig you can configure the UUID of the iBeacon which triggers the led, the pin the led is connected to and the timeout – in seconds – after which the program turns the led off if the iBeacon is not detected anymore. You can moreover set a power threshold to control the distance at which the iBeacon is detected.
To parse the received packet and get the UUID value, in my program I used the method described in this article (parsing using astruct).
The program verifies if the received packet (event ESP_GAP_SEARCH_INQ_RES_EVT) was sent by an iBeacon checking that the packet length is 30 bytes and that its header contains the values listed above:
Although many of us may have had childhood aspirations to be a famous wrestler in the WWE, not very many of us will ever realize those dreams. You can get close, though, if you have your own epic intro music theme that plays anytime you walk into a room. Although it’s not quite the same as entering a wrestling ring, [Matt]’s latest project will have you feeling just as good whenever you enter a room to your own theme song.
The core of the build consists of a boom box with an auxiliary input. The boom box is fed sound via a Raspberry Pi which also serves as the control center for the rest of the project. It runs Node.js and receives commands via websockets from a publicly accessible control server. The Pi is also running Spotify which allows a user to select a theme song, and whenever that user’s iBeacon is within range, the Pi will play that theme song over the stereo.
The project looks like it would be easy to adapt to any other stereo if you’re looking to build your own. Most of the instructions and code you’ll need are available on the project’s website, too. And, if you’re a fan of music playing whenever you open a door of some sort, this unique project is clearly the gold standard. It might even make Stone Cold Steve Austin jealous.