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BLE operation

In Bluetooth Low Energy mode, there are five link states that are negotiated by the host and device:

Advertising: Devices that transmit the advertising packets on the advertising channels.
Scanning: Devices that receive advertising on the advertising channels without intention to connect. Scanning can be active or passive:
- Active scanning: Link layer listens for advertising PDUs. Depending on the received PDU, it may request an advertiser to send additional information.
- Passive scanning: Link layer will only receive packets, transmission disabled.
Initiating: Devices that need to form a connection to another device listen for connectable advertising packets and initiate by sending a connect packet.
Connected: There is ...

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