Radio Notification on connection events as a Peripheral

This section clarifies the functionality of the Radio Notification feature when the SoftDevice operates as a Bluetooth low energy Peripheral.

Radio Notification events are as shown in the following figure.

Figure 1. Peripheral link with multiple packet exchange per connection event
Peripheral link with multiple packet exchange per connection event

To guarantee that the ACTIVE notification signal is available to the application at the configured time when a single peripheral link is established, the following condition must hold:

tndist + tradio < tinterval

For exceptions, see Maximum peripheral packet transfer per Bluetooth low energy Radio Event.

The SoftDevice will limit the length of a Radio Event (tradio), thereby reducing the maximum number of packets exchanged, to accommodate the selected tndist. Consecutive peripheral Radio Events with Radio Notification signals shows consecutive Radio Events with Radio Notification signal and illustrates the limitation in tradio which may be required to guarantee tndist is preserved.

Figure 2. Consecutive peripheral Radio Events with Radio Notification signals
Consecutive peripheral Radio Events with Radio Notification signals

Maximum peripheral packet transfer per Bluetooth low energy Radio Event shows the limitation on the maximum number of 27-byte packets which can be transferred per Radio Event for given combinations of tndist and tinterval.

Table 1. Maximum peripheral packet transfer per Bluetooth low energy Radio Event. The data in this table assumes symmetric connections using LE 1M PHY, 27-byte packets, and full-duplex with Bluetooth low energy connection event length configured to be 7.5 ms and Connection Event Length Extension disabled.
tndist tinterval
7.5 ms 10 ms ≥ 15 ms
800 6 6 6
1740 5 6 6
2680 4 6 6
3620 3 5 6
4560 2 4 6
5500 1 4 6