Bluetooth Low Energy role configuration

The S140 SoftDevice stack supports concurrent operation in multiple Bluetooth® Low Energy roles. The roles available can be configured when the S140 SoftDevice stack is enabled at runtime.

The SoftDevice provides a mechanism for enabling the number of central or peripheral roles the application can run concurrently, and for enabling Quality of Service (QoS) channel survey. The SoftDevice can be configured with multiple connections as a Central or a Peripheral. The SoftDevice supports running one connectable Advertiser or Broadcaster and one Scanner or Observer concurrently with the Bluetooth Low Energy connections.

An Initiator or a connectable Advertiser can only be started if the number of connections is less than the maximum supported.

When the SoftDevice is enabled, it will allocate memory for the connections the application has requested. The SoftDevice will make sure that it has enough buffers to avoid buffer starvation within a connection event if the application processes the SoftDevice events immediately when they are raised. The SoftDevice will also allocate memory for the QoS channel survey if the application has enabled it.

The SoftDevice supports per connection bandwidth configuration by giving the application control over the connection interval and the length of the connection event. By default, connections are set to have an event length of 3.75 ms. This is sufficient for three packet pairs in a connection event with the default 27 octet-long Link Layer (LL) payload for Data Channel PDUs, given that the PHY is Uncoded.

The connection bandwidth can be increased by enabling Connection Event Length Extension. See Connection timing with Connection Event Length Extension for more information. Enabling Connection Event Length Extension does not increase the size of the SoftDevice memory pools.

Bandwidth and multilink scheduling can affect each other. See Scheduling for details. Knowledge about multilink scheduling can be used to get improved performance on all links. Refer to Suggested intervals and windows for details about recommended configurations.