Bluetooth device sleeping

[FormerMember]

If BLE device is sleeping,is link layer connection terminated or the link layer connection is still valid..? if it is valid..how the master will know about the sleeping periods of slave..?

if it is not valid..how the master will know about the sleeping periods of slave..?

[Ulrich Myhre]

Hi,

Your question was not 100% clear, so I am assuming that you are asking about slave latency - a feature where the slave can choose to sleep for N connection intervals between each data packet without disconnecting. With this feature, the slave can sleep, but is not required to, and can therefore wake up early if there is data to send. This means that the master has to listen for every connection interval in case the slave wakes up early.

The master is also aware of the connection parameters, which slave latency is a part of, so purely theoretically it could sleep when the slave sleeps, but this is not how the spec has defined it.

[FormerMember]

what is sleeping..?

so according to spec what i understood is, the slave will listen and send packets in connection interval time and will sleep in remaining time..? is it true..?

what i thought of sleeping is, the device will terminate the link layer connection and will sleep and will start advertising again for connection...is it true..?

how ble is called low energy ..?

[Ulrich Myhre]

I am still not sure what you are asking about. There are multiple ways and levels to sleep, both as bluetooth and nRF chip features. If you mean putting the device to sleep, it will break the connection, yes. Then you also need to define a wake-up source (e.g. a button) so that your device will eventually wake up again. When you wake up, it is like being reset, so you have to start advertising or connecting again.

Slave latency, the feature I mentioned in the original answer, is a sort of semi-sleep where you are not shutting down the chip, but you are not turning on the radio very often.

BLE is called low energy due to its lower requirements for what constitutes a connection, which enables fairly minimalistic devices to work for months or years on one battery. The connections also focus more on reliability over low latency, which guarantees message arrival at some point in the future.