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I study the bluetooth low energy. During studying, I have a question.

As I know, possible data transaction Role is observer-broadcaster(connectionless) and central-peripheral(connection) in BLE. But, What I wonder is data transaction between observer and peripheral?? Is that possible?? In other words, Can observer scan the peripheral's broadcasting message?

If that is possible, Can central receive the broadcaster's advertising packet? and Can central scan the broadcaster's advertising packet?

user3859506
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1 Answers1

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An observer can scan the advertisements from the broadcaster, unless the advertiser (broadcaster)'s advertisements are of type nonconnectable.

There are two types of scanning in Bluetooth Smart (Bluetooth Low Energy): passive and active.

Passive scanning just listens to advertisements (which contains advertisement data).

Active scanning when an advertisement is received it sends a scan request and the advertiser then sends a scan response (which contains scan response data) back.

There are different types of advertisements in Bluetooth Smart:

  • general advertisement: The typical advertisement whereto connections can be initiated. It supports active scanning.
  • direct advertisement: The advertiser wants a particular device to connect to it instantly. It does not support active scanning and does not have any advertising data (except the connection addresses of both devices).
  • discoverable advertisement: The advertiser supports active scanning, but can not be connected to. (i.e. broadcast of data).
  • nonconnectable advertisement: The advertiser does not support active scanning, and can not be connected to. (i.e broadcast of data).
telephone
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  • How is that related to connectable peripherals? Even when you are not connectable you can still send advertisements. Advertisements are primarily used to establish connections but can also carry data that is usefull without establishing a connection. – paulgavrikov Apr 10 '18 at 14:15
  • Yes, these kinds of advertisements are called _Discovable advertisement_ and _Nonconnectable advertisement_ – telephone Apr 10 '18 at 14:20
  • Maybe you should edit the first sentence then. ("Yes, unless the advertising device is nonconnectable. ") – paulgavrikov Apr 10 '18 at 14:43
  • Agree. And I think @user3859506 mixes concepts – telephone Apr 11 '18 at 19:16
  • Non-connectable advertisement packets can of course be seen by an observer. The reason they are called Non-connectable is because you can't connect to devices that emit that kind of packets. – Emil Apr 11 '18 at 19:32