Classic Bluetooth and Low Energy

Bluetooth is two radio systems that share a name:

• Classic Bluetooth (BR/EDR) keeps a steady link. It carries high-quality audio, calls and file transfers. A new device answers the inquiry this computer sends while scanning, and pairing produces a link key.
• Bluetooth Low Energy sleeps between short, scheduled exchanges, which saves power. A device announces itself with short advertising packets. Pairing produces a long-term key and, when the device shares one, an identity key that recognizes the device behind its changing addresses. Most of what a Low Energy device offers is described in GATT: services that group characteristics, small values that can be read, written or subscribed to.

Many phones, headsets and earbuds have both radios. Bindrune works out which radios a device uses from what the device reports, says what it based that on, and explains every step of the timeline for those radios. For a device with both, it shows the state of each radio and lets you choose which one to connect over first. A connected Low Energy device also shows its GATT services, with their standard names, and lets you read their values.

Low Energy devices often use random addresses. A static random address may change when the device restarts, but never while it is running. A private address changes regularly, so the device can’t be tracked; when the device shares its identity key during pairing, Bindrune shows its fixed identity address instead.

The state of each radio and the choice of radio need BlueZ’s experimental features. Without them, the device page says what is missing.