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bluetooth
Boatman_Yang
Boatman_Yang

Reputation: 71

BLE connection interval

From BT snoop log below, found BLE central device and peripheral device got connected after a few loops of negotiation about connection parameters, include connection interval, connection latency and supervisor timeout etc.

As found in bt snoop log, the connection interval will be set to 1 second, my question is: Why not found the connection between them disappear 1 second later after they connected? What’s the real meaning of connection interval?

Upvotes: 2

Views: 3205

Answers (2)

Prasad Rane
Prasad Rane

Reputation: 742

enter image description here

BLE is a radio communication protocol that work in the 2.4GHz spectrum.

If you measure the radio current on a CRO, while it is in a connection, you will get a graph something similar to shown above. The peaks indicate that radio is turned ON. Between the peaks the device is sleeping to save power.

To put it simply, connection interval is the time interval between the peaks. Meaning it is the time for which the device sleeps after sending a packet and then wakes up to send a packet again.

This timing is synchronized between the two communication devices. It is like two people agreeing to meet at a particular time and place.

Upvotes: 1

ppatierno
ppatierno

Reputation: 10065

As you know BLE has a pillar that is to be low energy consumption. The main rule is turn on the radio as little as possible and turn off the radio as soon as possibile. When a connection is established the radio signal isn't always active even when a peer want to transmit. The transmission phase has the radio turns on and off more times. The connection interval is the time between two connection event and inside each connection event there is packets transmission. Suppose the peer wants to transmitt 10 packets : the radio signal is on for packets transmission (max 6 packets) then turned off for a time that is the connection interval ... now 6 packets are transmitted. After connection interval, the radio is turned on to transmit tha last 4 packets and so on. The connection interval can be from 7.5 ms and 4 s and it depends on both peers. Of course, lesser connection interval means high baud rate transmission but more power consumption and vice versa.

Paolo.

Upvotes: 1

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