Selecting Suitable Connection Parameters for Apple Devices#
For each Bluetooth connection, a set of parameters can be changed on the fly, depending on the application requirements. These include: connection interval, slave latency, and supervision timeout. For example, to minimize power consumption you can increase the connection interval and slave latency. This reduces the RF duty cycle and allows the peripheral to stay longer in sleep mode if there is no need to transmit any user data.
For more details about Bluetooth connections, see UG103.14: Application Development Fundamentals: Bluetooth® Smart Technology.
The master (typically a mobile device) controls which connection parameters are used. When master initiates a connection to a slave, it selects the default parameters that are used. The slave can request updating the connection parameters. However, the master can either accept or reject this request.
Depending on the master, different restrictions can apply on which parameter combinations are accepted. This document focuses on the recommendations for iOS devices specified by Apple.
Apple Bluetooth Device Guidelines#
The rules for selecting connection parameters for BLE peripherals that are defined in the document Accessory Design Guidelines for Apple Devices, available for download here.
The BLE connection parameters are discussed in section 25.6 Connection Parameters. For example, the minimum connection interval is specified as 15 ms. Note that the minimum interval allowed by the Bluetooth core specification is 7.5 ms.
At the time of writing this document, the latest version of the guideline document was R11 (dated 2019-11-12).