PM0237 datasheet(16/88 Pages) STMICROELECTRONICS

16 / 88 page

Bluetooth low energy technology

PM0237

16/88

DocID027104 Rev 2

A white list is a list of stored device addresses used by the device controller for filtering

devices. The white list content cannot be modified while it is being used. If the device is in

advertising state and is using a white list to filter the devices (scan requests or connection

requests), it has to disable advertising mode for changing its white list.

1.3.3

Scanning state

There are two types of scanning:

•

Passive scanning: it allows to receive advertisement data from an advertiser device

•

Active scanning: when an advertisement packet is received, device can send back a

Scan Request packet, in order to get a Scan Response from the advertiser. This allows

the scanner device to get additional information from the advertiser device.

The following scan parameters can be set:

•

Scanning type (passive or active)

•

Scan interval: how often the controller should scan

•

Scan window: for each scanning interval, it defines how long the device scans

•

Scan filter policy: it can accept all the advertising packets (default policy) or only the

ones on the white list.

Once the scan parameters are set, it is possible to enable the device scanning. The

controller of the scanner devices sends to upper layers any received advertising packets

within an Advertising Report event. This event includes the advertiser address, advertiser

data, and the received signal strength indication (RSSI) of this advertising packet. The RSSI

can be used with the transmit power level information included within the advertising

packets to determine the path-loss of the signal and identify how far the device is:

Path loss = Tx power – RSSI .

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