Bluetooth State Resynchronization After Standby Wake
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Solution Overview
Problem
Conventional wireless computing devices experience state mismatches between the SoC and short range wireless modules like Bluetooth upon resuming from a low power state, leading to lost connections and delays in reestablishing communication.
Innovation Solution
The method involves disabling and reenabling the short range wireless module, such as a Bluetooth module, into a known state before entering sleep mode, and scheduling an event notification to delay communication until the SoC is fully operational, using a kernel driver to manage the Bluetooth Low Energy scan mode and UART hardware flow control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the system enters low power state to conserve energy, then power consumption is reduced, but connection state synchronization between SoC and wireless module is lost
Solution Approach 1:
The system performs preliminary actions before entering low power state by saving the current connection state (connected, disconnected, or scanning) to a register. This preliminary state preservation enables the wireless module to resume communication without state mismatch after waking from low power mode, resolving the contradiction between power savings and connection reliability.
2Speed
If the wireless module resumes communication immediately after SoC exits low power state, then connection recovery is faster, but state mismatch causes communication failures
Solution Approach 1:
The system implements a feedback mechanism where the wireless module checks the saved connection state upon resuming from low power mode and compares it with the current state. Based on this feedback, the module adjusts its communication behavior - resuming immediately if states match, or waiting for reconnection commands if states differ - thereby achieving both fast recovery and reliable communication.
Solution Approach 2:
The wireless module dynamically adjusts its resumption behavior based on the saved state condition. When the saved state indicates connected or scanning, the module resumes communication immediately. When the saved state indicates disconnected, the module waits for reconnection commands. This dynamic adaptation resolves the contradiction between speed and reliability.
3Stability of the object's composition
If the system disables and reenables wireless connection before sleep mode, then the wireless module is placed in a known state, but additional control steps are required
Solution Approach 1:
The system employs self-service by automatically saving the connection state to a register before entering low power mode and using this saved state to guide the resumption process. The kernel driver and wireless module work together autonomously to manage state synchronization without requiring external intervention, achieving state stability while keeping the control process manageable.
Data Source
AI summary
This disclosure provides methods and apparatus for more quickly and reliably reestablishing short range wireless connections between a wireless computing device and paired peripheral devices after one or more processing units of the wireless computing device exit a low power state. An example method includes, prior to the one or more processing units entering the low power state, placing a short range wireless module of the wireless computing device into a known state, and then while exiting the low power state, scheduling an event notification to prevent the short range wireless module from communicating with the one or more processing units before the one or more processing units have fully exiting the low power stat.