PM0237 datasheet(17/88 Pages) STMICROELECTRONICS

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PM0237

Bluetooth low energy technology

1.3.4

Connection state

When data to be transmitted are more complex than the ones allowed by advertising data or

a bidirectional reliable communication between two devices is needed, the connection is

established.

When an initiator device receives an advertising packet from an advertising device to which

it wants to connect, it can send a connect request packet to the advertiser device. This

packet includes all the required information needed for establishing and handling the

connection between the two devices:

•

Access address used in the connection in order to identify communications on a

physical link

•

CRC initialization value

•

Transmit window size (timing window for first data packet)

•

Transmit window offset (offset of transmit window start)

•

Connection interval (time between two connection events)

•

Slave latency (number of times slave can ignore connection events before it is forced to

listen)

•

Supervision timeout (max time between two correctly received packets before link is

considered lost)

•

Channel map: 37 bits (1= good; 0 = bad)

•

Frequency-hop value (random number between 5 and 16).

•

Sleep clock accuracy range (used to determine the uncertainty window of the slave

device at connection event).

For a detailed description of the connection request packet refer to Bluetooth Specification

V4.0 [Vol 6], Section 2.3.3.

The allowed timing ranges are summarised in Table 7:

The transmit window starts after the end of the connection request packet plus the transmit

window offset plus a mandatory delay of 1.25 ms. When the transmit window starts, the

slave device enters in receiver mode and wait for a packet from the master device. If no

packet is received within this time, the slave leaves receiver mode, and it tries one

connection interval again later. When a connection is established, a master has to transmit a

packet to the slave on every connection event for allowing slave to send packets to the

master. Optionally, a slave device can skip a given number of connection events (slave

latency).

Table 7. Connection request timings intervals

Parameter

Min

Max

Note

Transmit window size

1.25 milliseconds

10 milliseconds

Transmit window Offset 0

Connection interval

Multiples of 1.25

milliseconds

Connection interval

7.5 milliseconds

4 seconds

Multiples of 1.25

milliseconds

Supervision Timeout

100 milliseconds

32 seconds

Multiples of 10

milliseconds

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