Biometric Sensor Wake Control Without USB Enumeration
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Solution Overview
Problem
Biometric sensors in computing devices often unnecessarily identify and transmit biometric signals, leading to repeated enumeration processes that consume time and computing resources, especially when the device is restarted or the lid is closed.
Innovation Solution
A biometric sensor with a first and second communication interface, along with input sensing circuitry and a controller, transmits a message to wake up the host and control the power state of the sensor, disabling the wake on fingerprint feature and placing it in a low power state when the lid is closed, and re-enabling it when the lid is opened, thus avoiding unnecessary enumeration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the biometric sensor continuously identifies and transmits biometric signals, then the sensor remains active and responsive, but computing resources are consumed and unnecessary enumeration processes occur
Solution Approach 1:
The biometric sensor dynamically changes its operational state based on host system conditions. When the host is in low-power mode or lid is closed, the sensor enters a low-power state where it does not continuously identify or transmit signals. When the host wakes up or lid is opened, the sensor transitions back to active state. This dynamic state adjustment resolves the contradiction by maintaining responsiveness when needed while conserving resources when idle.
Solution Approach 2:
The system implements feedback mechanisms where the sensor controller monitors host enumeration status and power states. Based on this feedback, the controller automatically adjusts sensor operation - disabling wake-on-fingerprint feature during host low-power states and re-enabling when host is active. This feedback loop ensures the sensor responds appropriately to system conditions without continuous resource consumption.
2Reliability
If the biometric sensor performs enumeration processes frequently, then device communication is maintained, but time and computing resources are wasted
Solution Approach 1:
The system performs preliminary actions by establishing communication pathways and device configurations during initial host startup or lid opening events. Once enumeration is complete and device configuration is established, the sensor maintains this configuration without performing repeated enumeration processes during subsequent idle periods. This preliminary action approach ensures communication reliability is established upfront while avoiding time-wasting repeated enumerations.
Solution Approach 2:
The system discards unnecessary enumeration processes during host low-power states or when lid is closed, while recovering and maintaining the essential device configuration and communication pathways. The sensor controller selectively disables non-essential enumeration operations while preserving the core communication framework, thus maintaining reliability without wasting time on redundant enumeration cycles.
3Speed
If the biometric sensor remains in active state, then it can detect inputs immediately, but power consumption increases
Solution Approach 1:
The biometric sensor implements dynamic power management by transitioning between active and low-power states based on host system conditions. When the host is active or lid is open, the sensor operates in full power mode for immediate input detection. When the host enters low-power mode or lid is closed, the sensor transitions to a low-power state with reduced consumption. This dynamic state management resolves the contradiction between speed and power consumption by adapting the sensor's operational intensity to actual system needs.
4Speed
If the wake on fingerprint feature is always enabled, then the sensor can wake the host immediately, but unnecessary wake attempts occur when the host is already in low-power mode
Solution Approach 1:
The sensor controller implements feedback monitoring of host power states before attempting wake operations. When the host is in low-power mode or lid is closed, the controller detects this state and disables the wake-on-fingerprint feature to prevent unnecessary wake attempts. When the host is active or lid is opened, the feature is re-enabled for immediate wake capability. This feedback-based control resolves the contradiction by enabling fast wake-up when needed while avoiding wasteful power consumption during inappropriate conditions.
Data Source
AI summary
In an example, a biometric sensor, includes a first communication interface to receive information associated with an enumeration of the biometric sensor from a host, a second communication interface, and input sensing circuitry to detect an input signal at the biometric sensor. The biometric sensor further includes a controller to, in response to detecting the input signal, transmit a message to wake up the host via the second communication interface, and in response to receiving an indication that a lid of the host has closed, control operation of the biometric sensor by placing the biometric sensor in a low power state.