CODEWITHSUNDEEP
bluetooth-lowenergy
Prasath
Prasath

Reputation: 57

Bluetooth Low Energy Max no of slaves

  1. In Bluetooth Low Energy, what is the maximum No. of slaves that can be connected to a master and what is the maximum No. of slaves a master can connect to?
  2. Bluetooth Low Energy has 40 channels but why are they only using 3 channels for advertisement and why they are placed between the wifi channels starting from channel 37, 38, 39?
  3. What is the maximum No. of slaves in Bluetooth LE 4.0 and 4.2?

Upvotes: 3

Views: 1922

Answers (2)

Mohammad Afaneh
Mohammad Afaneh

Reputation: 318

Tim Tisdall already answered 1&3 so no need to answer those questions.

As for 2, the spectrum used for BLE and WiFi overlap so there's no way to avoid using the same frequencies.

Channels 37, 38 and 39 in BLE are used for advertising and devices usually hop between these channels while advertising to maximize the possibility that a client will capture the advertisement. The rest of the channels (the other 37) are used for connections while data is being exchanged between a central and peripheral.

As for why they're only using 3, that's a design question that I won't be able to answer accurately but my guess is:

Not much is lost if you miss an advertisement since most devices continue advertising continuously vs. connection data which is much more crucial, hence the use of 37 channels for that and 3 for the advertisements.

Also, keep in mind that the channel numbers (37, 38, 39) are BLE specific and do not correspond to any channel numbers in WiFi. They are also not consecutively located within the spectrum (there are data channels located in between these):

Channel 37 -> 2402 MHz

Channel 38 -> 2426 MHz

Channel 39 -> 2480 MHz

Upvotes: 2

Tim Tisdall
Tim Tisdall

Reputation: 10392

1 & 3: Maximum no. of BLE Connection using BlueZ

Basically, there's no fixed limit to connections.

As for 2... I've never done anything with the channels because I think most things abstract over that. Bluetooth has always had issues with wifi because they both use the same unregulated frequency bands. I believe Bluetooth handles conflicts by channel hopping, but I don't know the specifics of how that works.

Upvotes: 3

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