The iPhone 17 series is unable to connect to the Bluetooth module BK3432.

When our Bluetooth device is scanned and a connection is initiated through the app on the iPhone 17, the air log shows that the iPhone sends an LL_LENGTH_REQ to execute the Data Length Update Procedure. However, our peripheral does not support the Bluetooth LE Data Length Extension, so it responds with an LL_UNKNOWN_RSP PDU with the UnknownType field set to LL_LENGTH_REQ.

After receiving the LL_UNKNOWN_RSP, the iPhone 17 does not proceed with the subsequent Bluetooth LE service discovery process. The connection is maintained until the peripheral actively disconnects.

Once the peripheral disconnects and continues broadcasting Bluetooth signals, the iPhone 17 repeatedly tries to connect to the peripheral and executes the aforementioned process, even if the app has been terminated.

According to the Bluetooth 4.2 core specification ([Vol. 6] Part B, Section 5.1.9), which can be found here: https://www.bluetooth.com/specifications/specs/core-specification-amended-4-2/, the iPhone should accept the LL_UNKNOWN_RSP and terminate the Data Length Update Procedure after receiving it, proceeding with the subsequent operations using the default minimum parameters.

Phenomenon: When the app calls the - (void)connectPeripheral:(CBPeripheral *)peripheral options:(nullable NSDictionary<NSString *, id> *)options method, the connection result callback is never received. After a period of approximately 10 seconds, it fails with a callback, displaying the message: central did fail to connect to peripheral: <TY : 45E4A697-31AE-9B5A-1C38-53D7CA624D8C, Error Domain=CoreBLEErrorDomain Code=400 "(null)">.