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Bluetooth piconet
Bluetooth devices connect via a micro-network known as a "piconet". Devices connect to each other in a master/slave relationship (since renamed "central/peripheral").
Prior to the establishment of a piconet, devices remain in discoverable/scanning mode.
At least one master and one slave is required to make a piconet however a master can have multiple slaves simultaneously (e.g. a computer with keyboard, mouse, speakers etc).
The master controls the connection timing and frequency modulation (necessary for the Bluetooth protocol) and the slave synchronises its clock with the master's. A slave can have its own controls (e.g. a set of headphones with playback controls) but it is the master that orchestrates the action.
What does this mean?
Take a mouse as a slave that is sending the click data to the master it is paired with. The mouse's microcontroller controls the click and what it "means" (although this is handled at a level up, in the application layer) but when the data is processed is managed by the master. The master controls:
- when devices can transmit
- what frequency they use
- the timing and synchronisation of the data exchanged
So in other words, the mouse waits for the master to give it a timeslot once the click has occurred. Then it's data is handed off to the application responsible on the master device.