Multi-Drop Digital Audio Bus Using Tri-Level Signaling

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Solution Overview

Problem

Existing digital audio bus technologies require significant device real estate, limiting aggressive form factor designs due to their need for multiple pins and complex protocols, which is not suitable for modern consumer electronics that prioritize cost, size, and power consumption.

Innovation Solution

A bidirectional time-division multiplexing (TDM) signaling protocol and tri-level signaling scheme enable multi-drop connectivity for real-time digital data transmission, allowing a single bus node to provide and receive clock and data signals, and implementing a simplified two-wire signaling conductor interface for single-ended signaling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing digital audio bus technologies are used, then reliable digital audio transmission is achieved, but device real estate (pins and packaging) increases

Engineering Contradiction:

Improvedigital audio transmission reliabilityVSAvoiddevice real estate

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines multiple signal functions (data, clock, control) into a single bidirectional bus interface. The TDM protocol multiplexes these signals over shared conductors, eliminating the need for separate dedicated pins for each function, thereby reducing device real estate while maintaining transmission reliability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bus interface is designed to perform multiple functions: bidirectional data transmission, clock signaling, and control operations all through the same physical medium. This multi-functional approach reduces the number of required pins compared to dedicated unidirectional interfaces

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If existing digital audio bus technologies are used, then digital audio transmission is achieved, but device complexity increases

Engineering Contradiction:

Improvedigital audio transmissionVSAvoidprotocol complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The TDM protocol uses periodic time slots to structure data transmission, with regular framing and synchronization intervals. This periodic structure simplifies the protocol logic compared to asynchronous protocols, as devices can anticipate signal patterns and use simple state machines to handle transmission and reception

Inventive Principle:

Principle #19Periodic action

3Adaptability or versatility

If more pins are used for digital audio bus, then transmission capability is improved, but manufacturing cost increases

Engineering Contradiction:

Improvetransmission capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

Multiple transmission functions are merged into a single bus interface, reducing pin count and thereby lowering manufacturing costs associated with pin fabrication, packaging, and assembly while maintaining comprehensive transmission capability through software-defined protocols

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10102175B2Methods and apparatus for multi-drop digital bus

Publication Date: 2018.10.16 APPLE INC

AI summary

Apparatus and methods for digital bus operation. In one embodiment, the digital bus is a bidirectional, time-division multiplexing (TDM) audio bus operation, and a bus technology is described that enables multi-drop (e.g., multiple device, multiple node, etc.) connectivity for real-time audio over a small form factor interface (e.g., as few as two (2) wires). Specifically, an exemplary tri-level signaling scheme provides bidirectional functionality, real-time clock edges, audio data, in a multi-drop topology in one implementation.