---
tags:
  - bluetooth
  - networks
---

# 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.
