Digital accessory interface calibration

• US 10,642,570 B2
• Filed: 10/31/2017
• Issued: 05/05/2020
• Est. Priority Date: 12/02/2014
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Zwart, Willem
• Primary Examiner(s): Saunders, Jr., Joseph
• Application Number:
  US15/798,608
• Publication Number:
  US 20180067715A1
• Time in Patent Office: 917 Days
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 3/165 Management of the audio stream, e.g. setting of volume, audio stream path

Abstract

A method of compensating for a round-trip transmission delay in an audio system comprising: a portable communications device; an audio accessory; and a cable, suitable for connecting the portable communications device and the audio accessory, having at least one wire and being detachable from at least one of the portable communications device and the audio accessory. At first times, a first synchronisation data pattern is transmitted on the at least one wire from said device to said accessory, wherein said first synchronisation data pattern comprises first signal level transitions on the at least one wire, synchronised to a master transmission clock. At second times, a second synchronisation data pattern is transmitted on the at least one wire from said accessory to said device, wherein said second synchronisation data pattern comprises second signal level transitions at timings that are set based on a delay value stored in said accessory. In the device, timings of said second signal level transitions as received at said device are determined relative to the master transmission clock, and timing delay control data based on said determination is transmitted from the device to the accessory. In the accessory, the timing delay control data is received, and the stored delay value is updated based on the timing delay control data.

Claims

1. A method of operation of a master device and a slave device connected by a half-duplex wired digital audio communications link, the method comprising, in at least a calibration mode:

the master device detecting a relative delay between transitions in data transmitted by the master device and transitions in data from the slave device as received by the master device;

the master device transmitting control data based on the relative delay to the slave device;

the slave device transmitting data with a delay, relative to the transitions in data as received from the master device, the delay being based on the transmitted control data.

2. A method as claimed in claim 1, wherein the step of the slave device transmitting data with a delay comprises:

the slave device updating a delay value stored in the slave device in response to the transmitted control data; and

the slave device transmitting data with a delay according to the stored delay value relative to the transitions in data as received from the master device.

3. A method as claimed in claim 1, further comprising:

the master device transmitting a first synchronisation data pattern to the slave device at first times on the wired link, wherein said first synchronisation data pattern comprises first signal level transitions on at least one wire of the wired link, said first signal level transitions being synchronised to a master transmission clock;

wherein the step of the slave transmitting data with a delay comprises;

the slave device transmitting a second synchronisation data pattern to the master device at second times on the wired link, wherein said second synchronisation data pattern comprises second signal level transitions, and wherein said second signal level transitions are at timings that are set based on the delay that is based on the transmitted control data.

4. A method as claimed in claim 3,

wherein the step of the master device detecting a relative delay between transitions in data transmitted by the master device and transitions in data from the slave device as received by the master comprises, in the master device:

determining, relative to the master transmission clock, timings of said second signal level transitions as received at said master device.

5. A method as claimed in claim 4, comprising, in the master device:

setting a desired timing relative to the master transmission clock;

determining whether said timings of said second signal level transitions as received at said master device are early or late relative to the desired timing; and

transmitting from the master device control data to retard or advance the timings of the second signal level transitions at said slave device, depending on whether said timings of said second signal level transitions as received at said master device are early or late relative to the desired timing.

6. A method as claimed in claim 5, comprising determining whether said timings of said second signal level transitions as received at said master device are early or late relative to the desired timing by comparing a signal level at the desired timing with an expected signal level at the desired timing.

7. A method as claimed in claim 5, wherein said desired timing relative to the master transmission clock provides a predetermined time margin at the master device between an end of a received symbol and a start of a transmitted symbol.

8. A method as claimed in claim 1, wherein said control data transmitted from the master device to the slave device directly represents the delay to be applied within the slave device.

9. A method as claimed in claim 1, wherein said control data transmitted by the master device comprises an indication of whether the delay needs to be increased or decreased.

10. An audio system, comprising a master device, a slave device, and a wired digital audio communications link between the master device and the slave device,

the master device being configured, in at least a calibration mode for detecting a relative delay between transitions in data transmitted by the master device and transitions in data from the slave device as received by the master device;

and

for transmitting control data based on the relative delay to the slave device; and

the slave being configured for transmitting data with a delay, relative to the transitions in data as received from the master device, the delay being based on the transmitted control data.

11. A method of operation of a master device connected by a half-duplex wired digital audio communications link to a slave device, the method comprising, in at least a calibration mode:

detecting a relative delay between transitions in data transmitted by the master device and transitions in data from the slave device as received by the master device; and

transmitting control data based on the relative delay to the slave device.

12. A method as claimed in claim 11, further comprising:

transmitting a first synchronisation data pattern to the slave device at first times on the wired link, wherein said first synchronisation data pattern comprises first signal level transitions on at least one wire of the wired link, said first signal level transitions being synchronised to a master transmission clock; and

receiving from the slave device on the wired link at second times a second synchronisation data pattern, wherein said second synchronisation data pattern comprises second signal level transitions.

13. A method as claimed in claim 12, wherein the step of detecting a relative delay between transitions in data transmitted by the master device and transitions in data from the slave device as received by the master device comprises:

determining, relative to the master transmission clock, timings of said second signal level transitions as received at said master device.

14. A master device, comprising:

a terminal for connection over a half-duplex wired digital audio communications link to a slave device, and

a controller, the controller being configured, in at least a calibration mode, for;

detecting a relative delay between transitions in data transmitted by the master device and transitions in data from the slave device as received by the master device; and

transmitting control data based on the relative delay to the slave device.

15. A master device in accordance with claim 14, comprising an audio codec.

16. A method of operation of a slave device connected by a half-duplex wired digital audio communications link to a master device, the method comprising, in at least a calibration mode:

receiving data from the master device, the data received from the master device having transitions therein;

receiving control data from the master device; and

transmitting data to the master device on the wired link, with transitions in the data being delayed, relative to the transitions in data as received from the master device, based on the received control data.

17. A method as claimed in claim 16, wherein the step of transmitting data to the master device on the wired link, with transitions in the data being delayed, relative to the transitions in data as received from the master device, based on the received control data, comprises:

updating a delay value stored in the slave device in response to the received control data; and

transmitting data to the master device on the wired link, with transitions in the data being delayed, relative to the transitions in data as received from the master device, according to the stored delay value.

18. A method as claimed in claim 16, further comprising:

receiving from the master device on the wired link at first times a first synchronisation data pattern, wherein said first synchronisation data pattern comprises first signal level transitions;

wherein the step of transmitting data to the master device on the wired link, with transitions in the data being delayed, relative to the transitions in data as received from the master device, based on the received control data comprises;

transmitting a second synchronisation data pattern to the master device on the wired link at second times, wherein said second synchronisation data pattern comprises second signal level transitions, and wherein said second signal level transitions are at timings that are set based on the delay that is based on the transmitted control data.

19. A slave device, comprising:

a terminal for connection over a half-duplex wired digital audio communications link to a master device, and

a controller, the controller being configured, in at least a calibration mode for;

receiving data from the master device, the data received from the master device having transitions therein;

receiving control data from the master device; and

transmitting data to the master device on the wired link, with transitions in the data being delayed, relative to the transitions in data as received from the master device, based on the received control data.

20. A slave device in accordance with claim 19, comprising a microphone/speaker module.