I2S Audio Bus Supervision via Word Clock Signal Processing
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Solution Overview
Problem
Current technologies fail to effectively monitor inter-chip audio paths and buses between semiconductor chips in alarm systems, which are crucial for ensuring the operational status of audio paths as required by standards like UL 864 9th Edition and 5527 3rd Edition, and this is not efficiently addressed with existing methods.
Innovation Solution
The integrated interchip sound (I2S) audio bus standard is used to process a reduced frequency signal, such as a 48 kHz Word Clock signal converted to a 12 kHz sine wave, which is placed on the I2S bus when audio signals are not present, allowing for monitoring of the audio paths without requiring additional circuitry, and this signal is used to verify the functionality of the voice path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current monitoring methods are used for external audio paths, then audio path monitoring is achieved, but inter-chip audio paths cannot be monitored
Solution Approach 1:
The I2S bus is designed to perform dual functions: carrying audio signals during normal operation and carrying supervision tones for monitoring when audio is absent. This multi-functionality allows the same physical infrastructure to serve both audio transmission and health monitoring purposes, enabling monitoring coverage for both external and inter-chip paths without requiring separate dedicated monitoring infrastructure.
2Reliability
If additional circuitry is added to monitor inter-chip audio paths, then monitoring capability is improved, but device complexity increases
Solution Approach 1:
The supervision tone generation, injection, and detection functions are merged into the existing I2S audio processing pipeline. The same digital signal processing resources that handle audio signals are reused to generate and monitor supervision tones, eliminating the need for separate dedicated monitoring circuitry and reducing overall device complexity while enabling inter-chip path monitoring.
Solution Approach 2:
Existing I2S bus infrastructure and processing resources are made multi-functional to perform both audio signal processing and supervision tone monitoring, eliminating the need for additional dedicated circuitry and reducing device complexity.
3Reliability
If the I2S bus carries only audio signals, then audio quality is maintained, but monitoring capability is lost
Solution Approach 1:
The I2S bus alternates between carrying audio signals and carrying supervision tones based on whether audio is present. When audio is absent, the supervision tone is injected; when audio is present, the supervision tone is suppressed. This periodic switching ensures that audio quality is maintained during audio transmission while enabling monitoring capability during idle periods.
Solution Approach 2:
The I2S bus dynamically switches its function between audio signal transmission and supervision tone transmission based on the presence of audio signals. This dynamic behavior allows the system to maintain audio quality when needed while enabling monitoring capability when the bus is idle, resolving the contradiction between audio purity and monitoring capability.
Data Source
AI summary
An approach for supervision of I2S bus audio paths employing a signal derived from a word clock signal of the I2S bus.