Methods and apparatus for multi-drop digital bus

• US 10,102,175 B2
• Filed: 03/17/2014
• Issued: 10/16/2018
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Breece, III, David, Hollabaugh, James, Kalinichev, Kirill
• Primary Examiner(s): Myers, Paul R
• Application Number:
  US14/216,370
• Publication Number:
  US 20140281076A1
• Time in Patent Office: 1,674 Days
• Field of Search: 710106
• CPC Class Codes: G06F 13/4072 Drivers or receivers G06F13/4086 takes precedence; for multistate logic circuits H03K19/0002
• CPC Class Codes: G06F 13/42 Bus transfer protocol, e.g. handshake; Synchronisation

Abstract

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.

Claims

1. A digital bus architecture within a given bus node of a plurality of bus nodes, comprising:

a time-division multiplexing (TDM) signaling protocol configured to transmit a clock signal comprising real-time digital data, the clock signal configured to enable multi-drop connectivity for the real-time digital data over a bus interface; and

the bus interface comprising a tri-level signaling scheme, the tri-level signaling scheme being configured to enable the given bus node to provide the clock signal and the real-time digital data to a plurality of other ones of the plurality of bus nodes;

wherein a data value of the real-time digital data at a time slot of the clock signal is indicated by a voltage level of the clock signal at the time slot;

wherein the tri-level signaling scheme is configured to enable a contention-based access to the bus interface;

wherein each of the plurality of bus nodes is configured to communicate with one another to select which of the plurality of bus nodes comprises the given bus node, the selected given bus node being configured to provide the real-time digital data to the plurality of other bus nodes;

wherein the contention-based access comprises a configuration of the plurality of bus nodes, the configuration of the plurality of bus nodes comprising an assignment of a corresponding time slot to each one of the plurality of other bus nodes; and

wherein subsequent to the configuration of the plurality of bus nodes, the given bus node is further configured to provide the real-time digital data to each one of the plurality of other bus nodes in accordance with the corresponding time slot assigned to each one of the plurality of other bus nodes.

2. The architecture of claim 1, wherein the tri-level signaling scheme is further configured to enable the bus node to receive the clock signal from any of the plurality of other bus nodes.

3. The architecture of claim 2, wherein the real time digital data comprises digital audio data having one or more quality of service requirements associated therewith.

4. The architecture of claim 2, wherein a data value of the real-time digital data is derived from a clock cycle of the clock signal.

5. The architecture of claim 2, wherein signaling of the tri-level signaling scheme is selected from a group consisting of:

(i) single-ended signaling and (ii) differential signaling.

6. The architecture of claim 1, wherein each of the plurality of other bus nodes is configured to transmit control information to the given bus node;

wherein each of the plurality of other bus nodes is allocated an upstream time slot for the transmission of the configuration information to the given node.

7. The architecture of claim 1, wherein the provision of the real-time digital data to each one of the plurality of other bus nodes in accordance with the corresponding time slot comprises provision of a first segment of audio data to a first one of the other bus nodes during a first time slot and provision of a second segment of audio data to a second one of the other bus nodes during a second time slot.

8. The architecture of claim 1, wherein the given bus node is further configured to provide a corresponding segment of the real-time digital data to each one of the plurality of other bus nodes in accordance with the corresponding time slot assigned to each one of the plurality of other bus nodes.

9. A method of operating a digital audio network comprising a plurality of bus nodes, wherein each bus node comprises one or more audio sources and/or one or more audio sinks, the method comprising:

arbitrating for control of the digital audio network, the arbitrating comprising dynamically determining which of the plurality of bus nodes comprises a central node;

receiving audio data to be transmitted to multiple other ones of the plurality of bus nodes of the digital audio network;

transmitting, based on the dynamic determining of which of the plurality of bus nodes comprises the central node, the audio data in accordance with time slots assigned to the multiple other ones of the plurality of bus nodes;

transmitting a real-time clock signal with edge transitions and logic levels; and

causing each edge transition of the real-time clock signal to convey a clock cycle of the received audio data, and causing each logic level of the real-time clock signal associated with the clock cycle to convey the received audio data.

10. The method of claim 9, wherein the transmitting of the real-time clock signal comprises transmitting the real-time clock signal to any of the plurality of bus nodes of the digital audio network.

11. The method of claim 9, wherein the transmitting comprises transmitting in accordance with a tri-level signaling scheme.

12. The method of claim 9, wherein the transmitting further comprises transmitting control data over a bidirectional link and transmitting the real-time clock signal over a unidirectional link.

13. The method of claim 9, wherein the arbitrating comprises allocating one or more time slots to at least one bus node for the transmitting.

14. The method of claim 9, wherein the transmitting of the real-time clock signal with the edge transitions and the logic levels comprises using the real-time clock cycle to convey the received audio data;

and

wherein the using of the real-time clock cycle to convey the received audio data comprises conveying the received audio data without using a timing circuit.

15. A simplified digital data interface, comprising:

a two-wire signaling conductor interface;

logic configured to implement a time-divided transmission protocol over the conductor interface so as to enable single-ended signaling for the reception of digital audio data; and

logic configured to detect a collision between two or more attempts at the reception of the digital audio data, and based on the detected collision, to wait a randomized period of time before allowing another attempt at the reception of the digital audio data;

wherein;

the digital audio data is transmitted in the form of a clock signal comprising a plurality of clock cycles;

the logic is further configured to derive a data value of the digital audio data from a logic level of the clock signal at a respective clock cycle of the plurality of clock signals; and

the time-divided transmission protocol is configured to enable transmission of the digital audio data in accordance with time slots assigned to one or more audio sinks, the clock signal being generated based on the assigned time slots.

16. The simplified digital data interface of claim 15, wherein:

the simplified digital data interface is assigned one or more time slots of the clock signal; and

data values are derived from the clock signal for the cycles that correspond with the assigned one or more time slots.

17. The simplified digital data interface of claim 15, wherein the one or more audio sinks comprise multiple bus nodes, each of the multiple bus nodes having an address assigned by an audio source.

18. The simplified digital data interface of claim 17, wherein:

the time-divided transmission protocol is further configured to enable transmission of the digital audio data in accordance with time slots assigned to the multiple audio sinks; and

the transmission of the digital audio data in accordance with time slots assigned to the multiple audio sinks comprises transmission of (i) a first channel of the digital audio data to a first audio sink during a first assigned time slot, (ii) a second channel of the digital audio data to a second audio sink during a second assigned time slot, and (iii) a third channel of the digital audio data to a third audio sink during a third assigned time slot.