PATENT DOCUMENT

Publication Number: US-9020162-B2
Application Number: US-201213494679-A
Country: US
Kind Code: B2

Title: Electronic device and external equipment with digital noise cancellation and digital audio path

Abstract:
Electronic devices and accessories are provided that may communicate over wired communications paths. The electronic devices may be portable electronic devices such as cellular telephones or media players and may have audio connectors such as 3.5 mm audio jacks. The accessories may be headsets or other equipment having mating 3.5 mm audio plugs and speakers for playing audio. Microphones may be included in an accessory to gather voice signals and noise cancellation signals. Analog-to-digital converter circuitry in the accessory may digitize the microphone signals. Digital voice signals and voice noise cancellation signals can be transmitted over the communications path and processed by audio digital signal processor circuitry in an electronic device. Digital-to-analog converter circuitry in the accessory may convert digital audio signals to analog speaker signals. Digital noise cancellation signals may use digital noise signals to cancel noise from digital audio signals that have been received from an electronic device.

Claims:
What is claimed is: 
     
       1. An electronic device that is coupled to a headset over a wired communications path, comprising:
 an audio connector coupled to the wired communications path; and 
 circuitry that receives digital voice microphone signals from the headset through the audio connector, the circuitry comprising a transceiver, wherein the audio connector comprises four contacts, and wherein the digital voice microphone signals comprise differential signals received by the transceiver over a pair of the contacts, using a differential signaling scheme. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the circuitry is configured to perform noise cancellation operations based at least partly on the digital voice microphone signals. 
     
     
       3. The electronic device defined in  claim 2  further comprising a digital-to-analog converter that produces analog output signals that are transmitted through the audio connector. 
     
     
       4. The electronic device defined in  claim 1  wherein the audio connector comprises a 3.5 mm audio connector. 
     
     
       5. The electronic device defined in  claim 1  wherein the audio connector comprises a four-contact audio jack. 
     
     
       6. The electronic device defined in  claim 1  wherein the circuitry comprises an audio digital signal processor. 
     
     
       7. The electronic device defined in  claim 1  wherein the circuitry comprises an audio digital signal processor that receives the digital voice microphone signals from a voice microphone in the headset and that receives digital voice noise cancellation signals from a noise cancellation microphone associated with the voice microphone in the headset and wherein the audio digital signal processor is configured to perform noise cancellation operations based at least partly on the digital voice microphone signals and the digital voice noise cancellation signals. 
     
     
       8. An electronic device that is coupled to a headset over a wired communications path, the electronic device comprising:
 an audio connector coupled to the wired communications path; 
 an audio digital signal processor that receives digital noise cancellation signals from the headset through the audio connector; and 
 a transceiver, wherein the audio connector comprises four contacts and wherein the digital noise cancellation signals comprise differential signals received by the transceiver over a pair of the contacts, using a differential signaling scheme. 
 
     
     
       9. The electronic device defined in  claim 8  wherein the electronic device is an electronic device selected from the group consisting of: a cellular telephone, a laptop computer, a tablet computer, an ultraportable computer, and a media player that has wireless communications capabilities. 
     
     
       10. The electronic device defined in  claim 8  wherein the audio digital signal processor is configured to perform noise cancellation operations based at least partly on the digital noise cancellation signals. 
     
     
       11. The electronic device defined in  claim 10  further comprising a digital-to-analog converter that produces analog output signals that are transmitted through the audio connector. 
     
     
       12. The electronic device defined in  claim 8  wherein the audio connector comprises a 3.5 mm audio connector. 
     
     
       13. The electronic device defined in  claim 8  wherein the audio connector comprises a four-contact audio jack. 
     
     
       14. The electronic device defined in  claim 8  further comprising a transceiver that transmits digital audio signals to the headset through the audio connector. 
     
     
       15. An electronic device that is coupled to a headset over a wired communications path, the electronic device comprising:
 an audio connector having four contacts; and 
 circuitry that transmits digital audio signals to the headset over at least a given one of the four contacts in the wired communications path and that receives digital audio signals from the headset over at least the given one of the four contacts in the wired communications path; 
 wherein the received digital audio signals comprise digital voice microphone signals and digital voice noise cancellation signals received from the headset through the audio connector and wherein the circuitry comprises an audio digital signal processor configured to perform noise cancellation operations based at least partly on the digital voice microphone signals and the digital voice noise cancellation signals. 
 
     
     
       16. The electronic device defined in  claim 15  wherein the audio connector comprises a 3.5 mm audio connector. 
     
     
       17. The electronic device defined in  claim 15  wherein the audio connector comprises a 3.5 mm audio connector and wherein the transmitted digital audio signals comprise right and left audio channels and at least one additional surround sound audio channel.

Description:
This application is a division of patent application Ser. No. 12/622,378, filed Nov. 11, 2009, which is hereby incorporated by referenced herein in its entirety. This application claims the benefit of and claims priority to patent application Ser. No. 12/622,378, filed Nov. 11, 2009. 
    
    
     BACKGROUND 
     Electronic devices such as computers, media players, and cellular telephones typically contain audio jacks. Accessories such as headsets have mating plugs. A user who desires to use a headset with an electronic device may connect the headset to the electronic device by inserting the headset plug into the mating audio jack on the electronic device. Miniature size (3.5 mm) phone jacks and plugs are commonly used electronic devices such as notebook computers and media players, because audio connectors such as these are relatively compact. 
     Headsets and other accessories have speakers that can be used to play back audio for a user. Some accessories have microphones. Microphones can be used to pick up the sound of a user&#39;s voice. This allows an electronic device to be used to record voice memos. Electronic devices with cellular telephone circuitry can use a microphone on an accessory to gather the user&#39;s voice during a telephone call. 
     In some headsets, microphones are used to form part of a noise cancellation circuit. When noise cancellation functions are active, the impact of ambient noise on audio playback can be reduced. Microphones can also be used to implement voice microphone noise cancellation. 
     Noise cancellation operations are generally implemented using analog noise cancellation circuitry. The analog noise cancellation circuitry subtracts a weighted version of the microphone signal from the audio signal. 
     Although conventional noise cancellation circuit arrangements can be satisfactory in some situations, recent advances in headphone quality and audio playback fidelity are placing increasing burdens on conventional noise cancellation circuits. These burdens are making it difficult or impossible to implement desired levels of noise cancellation performance with conventional approaches. 
     SUMMARY 
     Electronic devices and external equipment such as headsets and other accessories may handle digital audio signals. 
     An electronic device may be provided with audio digital signal processing circuitry and a transceiver. Switching circuitry may couple circuitry in the electronic device to an audio connector such as a 3.5 mm audio jack. 
     An accessory such as a headset may have a cable with a matching 3.5 mm audio connector. The accessory may have speakers. A voice microphone may be provided in the headset to gather a user&#39;s voice. 
     Noise cancellation microphones may be associated with the speakers and the voice microphone. Digital noise cancellation circuitry in the headset may reduce noise by processing digital audio signals and digital noise signals from the noise cancellation microphones. 
     Digital voice signals from the voice microphone and digital voice microphone noise signals from a noise cancellation microphone that is associated with the voice microphone may be transmitted from the headset to the electronic device. The electronic device may cancel noise in the voice signals by processing the digital voice signals and the digital voice microphone noise signals using the audio digital signal processing circuitry. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device in communication with an accessory such as a headset or other external equipment in a system in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram showing how a communications path that includes an audio connector can be used to allow a device and external equipment to interact in accordance with an embodiment of the present invention. 
         FIG. 3  is a schematic diagram showing illustrative circuitry that may be used in an electronic device to communicate with an accessory and to provide audio processing functions in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram of illustrative audio and communications circuitry in an accessory that communicates with circuitry in an electronic device such as the circuitry of  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 5  is a circuit diagram of illustrative communications circuitry in an accessory in accordance with an embodiment of the present invention. 
         FIG. 6  is a circuit diagram of an illustrative encoding circuit in accordance with an embodiment of the present invention. 
         FIG. 7  is a circuit diagram of an illustrative circuit that may be used to convert analog audio signals into digital audio signals in accordance with an embodiment of the present invention. 
         FIG. 8  is a circuit diagram of an illustrative digital noise cancellation circuit that may be used in an accessory in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic components such as electronic devices and other equipment may be interconnected using wired and wireless paths. For example, a wireless path may be used to connect a cellular telephone with a wireless base station. Wired paths may be used to connect electronic devices to equipment such as computer peripherals and audio accessories. As an example, a user may use a wired path to connect a portable music player to a headset. 
     Electronic devices that may be connected to external equipment using wired paths include desktop computers and portable electronic devices. The portable electronic devices that are connected to the external equipment in this way may include tablet computers, laptop computers, and small portable computers of the type that are sometimes referred to as ultraportables. The portable electronic devices may also include somewhat smaller portable electronic devices such as wrist-watch devices, pendant devices, and other wearable and miniature devices. 
     The electronic devices that are connected to external equipment using wired paths may also be handheld electronic devices such as cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, and handheld gaming devices. The electronic devices may be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid electronic devices include a cellular telephone that includes media player functionality, a gaming device that includes a wireless communications capability, a cellular telephone that includes game and email functions, and a portable device that receives email, supports mobile telephone calls, has music player functionality, and supports web browsing. These are merely illustrative examples. 
     An example of external equipment that may be connected to such an electronic device by a wired path is an accessory such as a headset. A headset typically includes a pair of speakers that a user can use to play audio from the electronic device. The accessory may have a user control interface such as one or more buttons. When a user supplies input, the input may be conveyed to the electronic device. As an example, when the user presses a button on the accessory, a corresponding signal may be provided to the electronic device to direct the electronic device to take an appropriate action. Because the button is located on the headset rather than on the electronic device, a user may place the electronic device at a remote location such as on a table or in a pocket, while controlling the device using conveniently located headset buttons. 
     The external equipment that is connected by the wired path may also include equipment such as a tape adapter. A tape adapter may have an audio plug on one end and a cassette at the other end that slides into a tape deck such as an automobile tape deck. Equipment such as a tape adapter may be used to play music or other audio over the speakers associated with the tape deck. Audio equipment such as the stereo system in a user&#39;s home or automobile may also be connected to an electronic device using a wired path. As an example, a user may connect a music player to an automobile sound system using a three-pin or four-pin audio connector (e.g., TRS or TRRS connectors). 
     In a typical scenario, the electronic device that is connected to the external equipment with the wired path produces audio signals. These audio signals may be transmitted to the external equipment in the form of analog and digital audio. The external equipment may include a voice microphone. One or more noise cancelling microphones may also be provided. Microphone signals (e.g., analog audio signals corresponding to a user&#39;s voice, ambient noise, or other sounds) may be processed locally in the accessory. Microphone signals may also be conveyed to the electronic device using the wired path. The wired path may be used to convey signals such as power signals and control signals in addition to audio signals. Digital data may be conveyed if desired. The digital data may include, for example, control signals, audio, display information, etc. 
     If the electronic device is a media player and is in the process of playing a song or other media file for the user, the electronic device may be directed to pause the currently playing media file when the user presses a button associated with attached external equipment. As another example, if the electronic device is a cellular telephone with media player capabilities and the user is listening to a song when an incoming telephone call is received, actuation of a button on an accessory or other external equipment by the user may direct the electronic device to answer the incoming telephone call. Actions such as these may be taken, for example, while the media player or cellular telephone is stowed within a user&#39;s pocket. 
     Accessories such as headsets are typically connected to electronic devices using audio plugs (male audio connectors) and mating audio jacks (female audio connectors). Audio connectors such as these may be provided in a variety of form factors. Most commonly, audio connectors take the form of 3.5 mm (⅛″) miniature plugs and jacks. Other sizes are also sometimes used such as 2.5 mm subminiature connectors and ¼ inch connectors. In the context of accessories such as headsets, these audio connectors and their associated cables can be used to carry analog signals such as audio signals for speakers and microphone signals. Digital data streams may also be used to convey audio signals (e.g., audio output signals such as played-back media or telephone call audio, microphone signals, and noise cancellation audio), control signals (e.g., input-output signals), clock information, and other signals. These digital signals may be conveyed over the 3.5 mm audio jack or other connectors. Optical connectors, which may be integrated with connectors such as audio jack connectors, may also be used to convey data between an electronic device and an associated accessory, particularly in environments that carry high bandwidth traffic such as video traffic. If desired, audio connectors such as 3.5 mm jacks and plugs may include optical communications structures to support this type of traffic. 
     The audio connectors that are used in connecting an electrical device to external equipment may have any suitable number of contacts. Stereo audio connectors typically have three contacts. The outermost end of an audio plug is typically referred to as the tip. The innermost portion of the plug is typically referred to as the sleeve. A ring contact lies between the tip and the sleeve. When using this terminology, stereo audio connectors such as these are sometimes referred to as tip-ring-sleeve (TRS) connectors. The sleeve can serve as ground. The tip contact can be used in conjunction with the sleeve to handle a left audio channel and the ring contact can be used in conjunction with the sleeve to handle the right channel of audio (as an example). In four-contact audio connectors, an additional ring contact is provided to form a connector of the type that is sometimes referred to as a tip-ring-ring-sleeve (TRRS) connector. Four-contact audio connectors may be used to handle a microphone signal, left and right audio channels, and ground (as an example). 
     Electrical devices and external equipment may be connected in various ways. For example, a user may connect either a pair of stereo headphones or a headset that contains stereo headphones and a microphone to a cellular telephone audio jack. Accessories such as these may include one or more noise cancelling microphones. For example, the voice microphone may have an associated noise cancellation microphone that picks up ambient noise in the vicinity of the voice microphone. The earbuds or other speakers in an accessory may also have noise cancellation microphones. For example, each earbud in a headset may have an external noise cancellation microphone on an outer surface of the earbud. In addition to the external noise cancellation microphone or instead of the external noise cancellation microphone, each earbud may have an internal noise cancellation microphone on an interior surface of the earbud (adjacent to the ear). 
     In accessories with more speakers, more noise cancellation microphones may be used. For example, additional noise cancellation microphones can be provided in earbuds that contain multiple drivers or in surround sound accessories. A surround sound accessory might, for example, have five or six speakers (or more) and might have a noise cancellation microphone that is adjacent to each respective speaker. 
     Electrical devices and external equipment may be operated in various modes. For example, a cellular telephone may be used in a music player mode to play back stereo audio to a user. When operated in telephone mode, the same cellular telephone may be used to play telephone call left and right audio signals to the user while simultaneously processing telephone call microphone signals from the user. Noise cancellation features may be selectively turned on and off as needed. For example, microphone noise cancellation may be activated while earbud noise cancellation features are deactivated (as an example). Noise cancellation functions can also be globally deactivated or globally activated. 
     Electronic devices and external equipment may be provided with path configuration circuitry that allows the electronic devices and external equipment to be operated in a variety of different operating modes in a variety of different combinations. When, for example, a user connects one type of accessory to an electronic device, the path configuration circuitry may be adjusted to form a first set of paths between the electronic device and accessory. When a user connects a different type of accessory, the path configuration circuitry may be adjusted to form a second set of paths between the electronic device and accessory. 
     The first and second sets of paths may, for example, be used to route power supply voltages and other signals to and from the pins of an audio connector in different ways depending on the mode in which the electronic device and accessory are being used. For example, if it is desired to power only a microphone or other component that draws low amounts of power, power can be supplied through a relatively high-impedance microphone bias path. If, however, larger amounts of power are desired to power noise cancelling circuitry or other circuitry in an accessory, a low-impedance power supply voltage line may be switched into use in place of the high-impedance microphone bias path. Other connections can also be adjusted (e.g., to route audio signals to desired locations, to change where other analog and/or digital signals are provided, etc.). 
     To provide high performance in an accessory that supports noise cancellation, it may be desirable to implement noise cancellation operations using digital audio processing circuitry. Digital audio processing may be more accurate than analog processing in some circumstances and may introduce less noise onto an audio signal. In schemes in which digital audio signals are conveyed from the accessory to the electronic device, the circuit resources of the electronic device may be used to help implement desired functions. This may help reduce the amount of circuitry that is included in a given accessory and may help minimize accessory power consumption. Digital audio processing may also be performed using digital processing circuitry that is primarily or exclusively implemented within an accessory. 
     In configurations in which at least some of the communications between the electronic device and accessory are implemented using digital communications, the capacity of the electronic device and accessory to communicate can be enhanced. For example, digital communications may allow numerous channels of audio to be conveyed between the electronic device and accessory in real time. Control signals and other signals may also be conveyed digitally. At the same time, the electronic device may, if desired, include analog circuitry that produces analog audio signals. When an accessory with digital communications capabilities is connected to the electronic device, the electronic device and accessory can communicate digitally. When an accessory without digital communications capabilities is connected to the electronic device, analog circuitry in the electronic device may supply analog audio signals to the accessory. For example, if a stereo headset with two speakers and no microphone or control capabilities is connected to the electronic device, analog audio circuitry may be used to supply left and right channels of analog audio to the speakers in the stereo headset. When a more advanced accessory is connected to the electronic device, additional features may become available (e.g., digital audio processing for noise reduction, digital control capabilities, additional audio streams for surround sound speakers, etc.). 
     An illustrative system in which an electronic device and external equipment may communicate over a wired path is shown in  FIG. 1 . As shown in  FIG. 1 , system  10  may include an electronic device such as electronic device  12  and external equipment  14 . External equipment  14  may be equipment such as an automobile with a sound system, consumer electronic equipment such as a television or audio receiver with audio capabilities, a peer device (e.g., another electronic device such as device  12 ), or any other suitable electronic equipment. In a typical scenario, which is sometimes described herein as an example, external equipment  14  may be an accessory that contains speakers such as a headset. External equipment  14  is therefore sometimes referred to as “accessory  14 ” or “headset  14 .” Speakers in accessory  14  may be provided as earbuds or as part of a headset or may be provided as a set of stand-alone powered or unpowered speakers (e.g., desktop speakers). As shown in  FIG. 1 , equipment  14  may include I/O circuitry  32  and storage and processing circuitry  26 . 
     A path such as path  16  may be used to connect electronic device  12  and accessory  14 . In a typical arrangement, path  16  includes one or more audio connectors such as 3.5 mm plugs and jacks or audio connectors of other suitable sizes. Conductive lines in path  16  may be used to convey signals over path  16 . There may, in general, be any suitable number of lines in path  16 . For example, there may be two, three, four, five, or more than five separate lines. These lines may be part of one or more cables. Cables may include solid wire, stranded wire, shielding, single ground structures, multi-ground structures, twisted pair structures, or any other suitable cabling structures. Extension cord and adapter arrangements may be used as part of path  16  if desired. In an adapter arrangement, some of the features of accessory  14  such as user interface and communications functions may be provided in the form of an adapter accessory with which an auxiliary accessory such as a headset may be connected to device  12 . 
     Electronic device  12  may be a desktop or portable computer, a portable electronic device such as a handheld electronic device that has wireless capabilities, equipment such as a television or audio receiver, or any other suitable electronic equipment. Electronic device  12  may be provided in the form of stand-alone equipment (e.g., a handheld device that is carried in the pocket of a user) or may be provided as an embedded system. Examples of systems in which device  12  may be embedded include automobiles, boats, airplanes, homes, security systems, media distribution systems for commercial and home applications, display equipment (e.g., computer monitors and televisions), etc. 
     Device  12  may include input-output circuitry  28  and storage and processing circuitry  30 . Input-output circuitry  28  of device  12  and input-output circuitry  32  of equipment  14  may include buttons, touch-sensitive components such as touch screens and touch pads, microphones, sensors, and other components for gathering input from a user. Input-output circuitry  32  and  28  may also include speakers, status inductors such as light-emitting diodes, displays, and other components for providing output to users. Circuitry  32  and  28  may also include digital and analog communications circuitry for supporting communications over path  16  and for supporting wireless communications. Storage and processing circuitry  26  and  30  may be based on microprocessors, application-specific integrated circuits, audio chips (codecs), video integrated circuits, microcontrollers, digital signal processors, memory devices such as solid state storage, volatile memory, and hard disk drives, etc. 
     Device  12  may communicate with network equipment such as equipment  18  over path  22 . Path  22  may be, for example, a cellular telephone wireless path. Equipment  18  may be, for example, a cellular telephone network. Device  12  and network equipment  18  may communicate over path  22  when it is desired to connect device  12  to a cellular telephone network (e.g., to handle voice telephone calls to transfer data over cellular telephone links, etc.). 
     Device  12  may also communicate with equipment such as computing equipment  20  over path  24 . Path  24  may be a wired or wireless path. Computing equipment  20  may be a computer, a set-top box, audio-visual equipment such as a receiver, a disc player or other media player, a game console, a network extender box, or any other suitable equipment. 
     In a typical scenario, device  12  may be, as an example, a handheld device that has media player and cellular telephone capabilities (sometimes referred to collectively as a cellular telephone). Accessory  14  may be a headset with a microphone and a user input interface such as a button-based interface for gathering user input. Path  16  may be a four or five conductor audio cable that is connected to devices  12  and  14  using 3.5 mm audio jacks and plugs (as an example). Computing equipment  20  may be a computer with which device  12  communicates (e.g., to synchronize a list of contacts, media files, etc.). 
     While paths such as path  24  may be based on commonly available digital connectors such as USB or IEEE 1394 connectors, it may be advantageous to use standard audio connectors such as a 3.5 mm audio connector to connect device  12  to accessory  14 . Connectors such as these are in wide use for handling audio signals. As a result, many users have a collection of headsets and other accessories that use 3.5 mm audio connectors. The use of audio connectors such as these may therefore be helpful to users who would like to connect their existing audio equipment to device  12 . Consider, as an example, a user of a media player device. Media players are well known devices for playing media files such as audio files and video files that contain an audio track. Many owners of media players own one or more headsets that have audio plugs that are compatible with standard audio jacks. It would therefore be helpful to users such as these to provide device  12  with such a compatible audio jack, notwithstanding the potential availability of additional ports such as USB and IEEE 1394 high speed digital data ports for communicating with external devices such as computing equipment  20 . 
     In system  10 , electronic device  12  and accessory  14  may include switching circuitry (also sometimes referred to as adjustable path configuration circuitry) that can be used to selectively interconnect various circuits to the contacts in the audio connectors of path  16 . The switching circuitry may be adjusted to support different modes of operation. These different modes of operation may result from different combinations of accessories and electronic devices, scenarios in which different device applications are active, etc. The switching circuitry may be formed from one or more transistor-based switches. If desired, the switching circuitry may include hybrid circuits that can be selectively switched into use. When the hybrid circuits are not actively used, the communications line to which they are connected may be used for unidirectional communications. When the hybrid circuits are switched into active use, the same communications line may be used to support bidirectional signals (e.g., an outgoing left or right audio channel in one direction and an incoming microphone signal in the opposite direction). Bidirectionality may also be supported using time multiplexing protocols. 
     Illustrative circuitry that may be associated with path  16  is shown in  FIG. 2 . Switching circuitry  160  may be provided in electronic device  12  and switching circuitry  162  may be provided in accessory  14  or other external equipment. Wired path  16  may be used to connect electronic device  12  and accessory  14 . Path  16  may include audio connectors such as audio connectors  34  and  38 . 
     The audio connectors of path  16  may include an audio plug such as plug  34  (i.e., a male audio connector). Plug  34  may mate with a corresponding audio jack such as audio jack  38  (i.e., a female audio connector). Connectors  34  and  38  may be used at any suitable location or locations within path  16 . For example, audio jacks such as jack  38  can be formed within the housing of device  12  and plugs such as plug  34  can be formed on the end of a cable such as cable  70  that is associated with a headset or other accessory  14 . As shown in  FIG. 2 , cable  70  may be connected to audio plug  34  via strain-relief plug structure  66 . Structures such as structure  66  may be formed with an external insulator such as plastic (as an example). 
     Audio plug  34  is an example of a four-contact plug. A four-contact plug has four conductive regions that mate with four corresponding conductive regions in a four-contact jack such as jack  38 . As shown in  FIG. 2 , these regions may include a tip region such as region  48 , ring regions such as rings  50  and  52 , and a sleeve region such as region  54 . These regions surround the cylindrical surface of plug  34  and are separated by insulating regions  56 . When plug  34  is inserted in mating jack  38 , tip region  48  may make electrical contact with jack tip contact  74 , rings  50  and  52  may mate with respective ring regions  76  and  78 , and sleeve  54  may make contact with sleeve terminal  80 . Insulating regions  56  may separate the contacts in jack  38 . In a typical configuration, there are four wires  88  in cable  70 , each of which is electrically connected to a respective contact in plug  34 . 
     Switching circuitry  160  may receive analog signals via path  170 . For example, switching circuitry  160  may receive analog audio output signals on path  170  and may switch these signals onto lines  168  when operating in an analog output mode to support legacy analog accessories. Switching circuitry  160  may handle digital signals using path  172 . For example, when operating in a digital audio mode to support a digital-ready headset, switching circuitry  160  may switch digital audio streams that are received on path  172  onto lines  168 . 
     Accessories may have fixed operating modes or adjustable operating modes. For example, a legacy analog headset may only operate in an analog audio mode. As another example, a digital-capable headset may operate in both analog and digital modes. This type of multimode operation may allow a digital-capable headset to revert to an analog audio mode when used with a legacy music player. To accommodate multiple operating modes, accessory  14  may control the configuration of the switches in switching circuitry  164 . When operating in analog audio mode, analog signals that are being conveyed between device  12  and accessory  14  can be routed through analog lines  174 . When operating in digital audio mode, switching circuitry  164  can be configured to connect digital path  176  into place. These switch configurations need not be mutually exclusive. For example, switching circuitry  160  and  164  may, if desired, be placed into configurations in which a mixture of analog and digital signals are conveyed over path  16 . A typical mixture of signals over path  16  might include power signals, control signals, and audio signals. Switching circuitry  164  may, if desired, be used to switch an ultrasonic tone generation circuit into use (e.g., to send ultrasonic tone codes from accessory  14  to device  12  that correspond to button press events or other user input). 
     The signal assignments that are used in the audio connectors of path  16  depend on the type of electronic device and accessory being used and the active operating mode for the system. For example, when operating in a legacy analog mode, ring contact  52  may serve as ground (and may therefore sometimes be referred to as the G contact of plug  34 ), tip  48  may be associated with left channel audio (and may therefore sometimes be referred to as the L contact of plug  34 ), ring  50  may be associated with right channel audio (and may therefore sometimes be referred to as the R contact of plug  34 ), and sleeve  54  may be associated with microphone signals (and may therefore sometimes be referred to as the M contact of plug  34 ). The mating contacts of jack  38  may have corresponding signal assignments. 
     As shown in  FIG. 3 , electronic device  12  may contain audio, communications, and control circuitry  180 . Circuitry  180  may include an audio circuit such as circuit  182 . Audio circuit  182 , which is sometimes referred to as a codec or audio codec, may include analog-to-digital (A/D) converter circuitry  184  and digital-to-analog (D/A) converter circuitry  186 . Analog-to-digital converter circuitry in device  12  may be used to digitize analog signals such as analog audio signals. For example, analog-to-digital converter circuitry  184  may be used to digitize one or more analog microphone signals. These microphone signals may be received from accessory  14  over path  16  or may be received from microphone equipment in device  12 . Digital-to-analog converter circuitry  186  may be used to generate analog output signals. For example, digital-to-analog converter circuitry  186  may receive digital signals corresponding to the audio portion of a media playback event, audio for a telephone call, noise cancellation signals, an alert tone or signal (e.g., a beep or ring), or any other digital information. Based on this digital information, digital-to-analog converter circuitry  186  may produce corresponding analog signals (e.g., analog audio). 
     Audio digital signal processor  188  may be used to perform digital signal processing on digitized audio signals. For example, if operating accessory  14  in a voice microphone noise cancellation mode, digital noise cancellation signals from a voice microphone noise cancellation microphone in accessory  14  may be conveyed over path  16  to audio digital signal processor  188 . Audio digital signal processor  188  may also receive digital audio voice signals from the voice microphone in accessory  14 . Using the processing capabilities of audio digital signal processor  188 , the digital noise cancellation microphone signals from accessory  14  can be digitally removed from the digital audio voice signal. Use of the processing power of device  12  in this way may help to reduce the processing burden that is placed on accessory  14 . This may allow accessory  14  to be constructed from less costly and less complex circuitry. Power consumption efficiency and audio performance may also be enhanced. If desired, digital audio processing circuitry in accessory  14  can be used to supplement or replace the audio processing functions of audio digital signal processor  188 . For example, digital noise cancellation circuitry in accessory  14  may be used in cancelling noise for the speakers of accessory  14 . 
     Transceiver  190  may be used to support unidirectional or bidirectional digital communications with a corresponding transceiver in accessory  14  over path  16 . Any suitable communications protocol may be used. For example, a protocol may be used that includes functions such as error correction functions. Data may be sent in packets or other suitable data structures. A clock that is produced by circuitry  180  of  FIG. 3  (e.g., by circuitry in transceiver  190 ) may be transmitted with the data. For example, transceiver  190  may embed a variable clock in a transmitted digital data stream. The clock, which is sometimes referred to as a data clock, may have a frequency in the range of 1 MHz to 32 MHz (as an example). 
     Switching circuitry such as switching circuitry  160  of  FIG. 2  may be used to selectively connect the contacts of audio connector  38  to the circuits of audio, communications, and control circuitry  180 . For example, when it is desired to supply analog audio output signals from codec  182  to connector  38 , the switching circuitry can be adjusted accordingly by the control and processing circuitry of device  12 . When it is desired to route digital signals to the audio contacts of audio connector  38 , the switching circuitry can be used to connect transceiver  190  to audio connector  38 . Power signals and other signals can also be selectively routed to connector  38  by switching circuitry  160 . 
     Illustrative circuitry that may be used to handle digital audio signal processing tasks for accessory  14  is shown in  FIG. 4 . As shown in  FIG. 4 , accessory  14  may include control circuitry  192 . Control circuitry  192  may include analog-to-digital and digital-to-analog converter circuitry. Data interface circuitry  194  may include transceiver circuitry for communicating with transceiver  190  of device  12  ( FIG. 3 ). Data interface circuitry  194  may also include circuitry for extracting an embedded clock (data clock) from the digital signals that are transmitted from device  12  over path  16 . The contacts in connector  34  (M, L, R, and G) may be selectively connected to the circuitry in accessory  14  by switching circuitry such as switching circuitry  164  of  FIG. 2 . For example, the L and R contacts may be connected to data interface  194  and the M and G contacts may be routed respectively to a positive power supply terminal and a ground terminal in accessory  14  (e.g., to deliver power received from device  12  to circuitry in accessory  14 ). 
     In the example of  FIG. 4 , accessory  14  has four microphones. Voice microphone  196  may be used to gather audio from a user&#39;s voice during a telephone call or may be used to record audio clips (as examples). Microphone  198  may serve as a noise cancellation microphone for voice microphone  196 . Speakers  204  and  206  may be used to play audio to a user. When presenting a user with stereo audio, for example, speaker  204  may be used to play left channel audio and speaker  206  may be used to play right channel audio. Microphone  200  may serve as a noise cancellation microphone for speaker  204 . Microphone  202  may serve as a noise cancellation microphone for speaker  206 . 
     When playing back audio for a user, digital audio signals may be received from device  12 . For example, data interface  194  may receive digital data streams (e.g., using L and R contacts in connector  34 ). Digital audio signals may be routed from interface  194  to encoder circuits  214  and  212  (e.g., sigma-delta encoders) over paths  210  and  208 , respectively. The encoded digital outputs of encoders  214  and  212  may be provided to respective digital noise cancellation circuits  216  and  218 . Circuits  216  and  218  may use information on ambient noise from noise cancellation microphones  200  and  202  to reduce noise in the played back audio signals (i.e., to implement noise cancellation for speakers  204  and  206 ). 
     The outputs of digital noise cancellation circuits  216  and  218  may be provided to digital-to-analog converter circuitry such as sigma-delta digital-to-analog converters  220  and  222 . Corresponding analog audio output signals from circuits  220  and  222  may be amplified using speaker drivers (amplifiers)  224  and  226 . The output of amplifier  224  may be provided to speaker  204 . The output of amplifier  226  may be provided to speaker  206 . 
     Microphones  196 ,  198 ,  200 , and  202  may produce analog microphone signals that are digitized using respective sigma-delta analog-to-digital converters  228 ,  230 ,  232 , and  240 . The outputs of converters  228 ,  230 ,  232 , and  240  may be digitally filtered (e.g., using respective decimation filters such as filters  234 ,  236 ,  238 , and  242 ). 
     Noise cancellation operations for voice microphone  196  may be performed in device  12 . For example, digital audio streams from voice microphone  196  and corresponding noise cancellation microphone  198  may be transmitted to audio digital signal processor  188  ( FIG. 3 ) for noise cancellation processing. 
     Noise cancellation operations for speakers  200  and  202  may be performed locally in accessory  14  using circuitry  192 . For example, noise cancellation microphone signals from noise cancellation microphone  200  may be routed to digital noise cancellation circuit  216  using path  244 . Similarly, noise cancellation microphone signals from noise cancellation microphone  202  may be routed to digital noise cancellation circuit  218  using path  246 . 
     Illustrative circuitry that may be used in implementing data interface  194  is shown in  FIG. 5 . As shown in  FIG. 5 , the L and R contacts of connector  34  may be coupled to inputs  252  and  250  of input amplifier  254  (e.g., using series termination resistors). Amplifier  254  may be a differential amplifier that converts differential data on lines  252  and  250  into single-ended data (i.e., data signals referenced to ground) on output  256 . The signals that are received at the input to amplifier  254  may be, for example, low-voltage differential signals having frequencies (bit rates) of 1-32 MHz and voltages of 2-400 mV (as an example). The rate at which signals are transmitted can be selected from a set of predefined rates (e.g., based on a variable clock at 6 MHz, 12 MHz, and 24 MHz). High clock rates can be used when high data transfer capabilities are desired and low clock rates can be used when high data transfer capabilities are not required (e.g., when it is desired to lower the clock rate to minimize radiated emissions and to conserve power). The use of low-voltage differential signaling schemes for path  16  may help minimize interference and reduce undesired radiation from cable  70  ( FIG. 2 ). Symmetrical or asymmetrical bidirectional communications may be supported over path  16 . For example, upstream data transfers from device  12  to accessory  14  may be performed at up to 12 Mbps (e.g., to convey up to 5 channels of audio output of up to 24 bits each at up to 96 kHz) and downstream data transfers from accessory  14  to device  12  may be performed at up to 4 Mbps (e.g., to convey up to 5 channels of microphone signals of up to 16 bits each at up to 48 kHz). 
     Received data from the output of input amplifier (buffer)  254  may be provided to transceiver module  266 . Transceiver module  266  may provide the received data to input-output first-in-first-out (FIFO) buffer  274 . During data transmission operations, data may be provided from buffer  274  to transceiver module  266  and may be driven onto the L and R contacts using output line  258 , differential output amplifier  260 , and differential outputs  262  and  264 . 
     The digital data stream that is received by transceiver module  266  may have an associated (e.g., embedded) clock. This clock can be extracted from the incoming data stream using clock and data recovery circuitry in circuit  194  (e.g., circuitry in transceiver module  266 ). Transceiver  266  can output the extracted clock as a data clock signal or can use extracted clock information to adjust a data clock signal produced by data clock  270 . 
     Data clock signal DCLK is received at clock input  272  of buffer  274  and clocks data into and out of the registers of buffer  274  during operation. When receiving data from path  16 , data is clocked into buffer  274  from transceiver  274  using path  288 . Corresponding digital audio signals may be supplied at outputs  278  and  280 . For example, a stream of digital audio data DL for a left audio channel may be supplied at path  278  and a stream of digital audio data DR for a right audio channel may be supplied at path  280 . When transmitting digital data to device  12  over path  16 , digital data may be received at inputs  276  of buffer  274 . After flowing through buffer  274 , this data may be provided to transceiver module  266  over path  288 . Paths  276  may be, for example, 16-bit or 32-bit buses that are connected to the outputs of decimation filters  234 ,  236 ,  238 , and  242  ( FIG. 4 ). 
     An audio clock signal ACLK may be produced based on the received clock. Audio clock signal ACLK may be produced at output  286  of audio clock circuit  284 . Transceiver circuitry  190  of  FIG. 3  can transmit periodic time stamps from device  12  to accessory  14 . Control circuit  282  may receive the periodic time stamps from transceiver  266  and buffer  274  and can adjust audio clock circuit  284  to ensure that audio clock signal ACLK is accurate. 
     Divider  290  may receive audio clock signal ACLK via path  294  and may divide ACLK (e.g., by 64 or other suitable number) to produce a corresponding lower-frequency sample clock signals SCLK on output line  292 . Sample clock SCLK and audio clock ACLK may be used in audio signal processing operations in circuitry  192 . 
     As shown in  FIG. 6 , for example, audio clock ALCK may be provided to clock input  296  of sigma-delta encoder  302  and sample clock SCLK may be provide to sample clock input  298  of sigma-delta encoder  302 . Circuitry of the type shown in  FIG. 6  may be used for sigma-delta encoders such as encoders  214  and  212  of  FIG. 4 . Digital data from transceiver  266  ( FIG. 4 ) may be provided to input  300  and corresponding sigma-delta encoded digital output data (of width n corresponding to the width of encoder  302 ) may be supplied at encoder output  304 . The data on path  300  may be clocked into encoder  302  using clock SLCK. The data on path  304  may be clocked out of encoder  302  using clock ACLK. As shown in  FIG. 4 , the output of sigma-delta encoder  214 , which may be used to handle left channel digital audio, may be supplied to digital noise cancellation circuit  216 . The output of sigma-delta encoder  212 , which may be used to handle right channel digital audio, may be supplied to digital noise cancellation circuit  218 . 
       FIG. 7  shows illustrative circuitry that may be used to handle analog-to-digital conversion operations in circuit  192 . Audio clock circuit  284  ( FIG. 5 ) may supply audio clock signal ACLK to audio clock input  312  of sigma-delta analog-to-digital converter  310 . Converter  310  (i.e., one of converters  228 ,  230 ,  232 , and  240  of  FIG. 4 ), may receive analog input at input  308  (i.e., analog input from one of microphones  196 ,  198 ,  200 , and  202  in  FIG. 4 ). Sigma-delta analog-to-digital converter  310  may digitize the analog input on input  308  and may supply a corresponding digital output on output  314 . Decimation filter  316  (i.e., one of decimation filters  342 ,  236 ,  238 , and  242  of  FIG. 4 ), may filter the digital signal on path  314  and may produce a corresponding filtered output on path  318 . Decimation filter  316  may be clocked using sample clock SCLK. Audio clock  284  may produce audio clock signal ACLK. Divider  290  (e.g., a divide-by-64 divider circuit) may divide clock ACLK for path  294  to produce sample clock SCLK on path  292 . Sample clock SCLK may be received at clock input  320  of decimation filter  316 . 
     Digitized voice microphone signals from microphone  196  and digitized noise cancellation microphone signals from voice noise cancellation microphone  198  may be provided from the outputs of decimation filters  234  and  236  for transmission to device  12  over path  16  by transceiver  266 . Device  12  may use audio digital signal processor  188  to process these signals. For example, audio digital signal processor  188  may remove noise from the voice microphone signal using the noise cancellation microphone signals from microphone  198 . 
     If desired, transceiver  266  may also transmit noise cancellation microphone signals from noise cancellation microphones  200  and  202  to device  12 . Audio digital signal processor  188  may also process noise cancellation signals from speaker noise cancellation microphones  200  and  202 . However, there can be latencies associated with passing signals through decimation filters. To minimize delays and thereby ensure satisfactory noise cancellation for speakers  204  and  206 , it may be preferable to perform digital audio processing functions for speaker noise cancellation using circuits such as digital noise cancellation circuits  216  and  218  of  FIG. 4 . Illustrative circuitry  322  that may be used in implementing noise cancellation circuits  216  and  218  is shown in  FIG. 8 . 
     As shown in  FIG. 8 , digital noise cancellation circuitry  322  may receive digital audio on path  326 . For example, circuitry  322  may receive output from encoder  214  or  212  of  FIG. 4 . The digital audio may correspond to left or right channel audio output from device  12  (as examples). Path  332  may be used to route the digital audio from path  326  to digital combiner circuit  328 . Digital combiner circuit  328  may also receive digital input from path  330 . Path  330  receives microphone noise cancellation signals from adjustable gain stage  334 . Adjustable gain stage  334  also provides microphone noise cancellation signals to path  324 . Path  324  may be used to provide the microphone noise cancellation signals to a decimation filter such as filter  238  or  242  of  FIG. 4 . 
     During typical operations, the digital audio signals on path  332  correspond to unmodified audio output and the signals on path  330  include ambient noise gathered from an appropriate noise cancellation microphone. Noise cancellation signals may be received on path  340  (i.e., from microphone  200  or  202  of  FIG. 4 ). Sigma-delta analog to digital converter  336  converts the analog microphone signals on path  340  into corresponding digital microphone signals (digital noise signals) on path  338 . 
     Optional adjustable gain stage  334  may be included in the path between microphone input  340  and input  330  to digital combiner circuit  328 . Adjustable gain stage  334  may be used to impose a frequency-dependent gain characteristic between path  338  at the output of sigma-delta analog-to-digital converter  336  and paths  324  and  330 . The frequency-dependent gain of gain stage  334  may be adjusted during operation of circuit  322 . For example, the user of accessory  14  may adjust the gain characteristic of gain stage  334  to change the frequency components of the currently playing audio signal (e.g., to accentuate the bass portion of the signal or to accentuate the treble portion of the signal). In this way, adjustable gain stage  334  may be used to allow circuitry  322  to serve as an equalization circuit (e.g., to accommodate user audio preferences, to implement a frequency-dependent weighting scheme that models the way in which noise is perceived at the ear of the user, etc.). Adjustable gain stage  334  performs frequency-dependent weighting operations digitally (i.e., by weighting the digital output of analog-to-digital converter  336 ). 
     Circuit  322  may used feed-forward and feedback signal contributions to implement noise cancellation. Signals on path  326  may be converted to analog signals by sigma-delta digital-to-analog converter  350 . These signals represent a “feed-forward” contribution to the analog output audio signal (analog speaker signal) on path  352 . Microphone feedback may be received from the noise cancellation microphone using path  340 . 
     The noise cancellation microphone that provides signals to path  340  (i.e., noise cancellation microphone  200  or  202  of  FIG. 4 ) may be located within an earbud adjacent to a speaker (i.e., adjacent to speaker  204  or  206 ). In this configuration, the noise cancellation microphone will pick up both audio output (feedback) and ambient noise. Circuit  322  may isolate the noise component of the noise cancellation microphone signal by digitally combining the signal on path  330  with the signal on path  332  using digital combiner circuit  328  (e.g., by subtracting the audio output signal from the combined audio and microphone signal). The resulting digital audio signal on path  354  represents the ambient noise that is to be cancelled. Signals on output  354  of circuit  328  may be filtered using filter  342  and may be converted from digital to analog using sigma-delta digital-to-analog converter  344 . The analog output of digital-to-analog converter  344  may be integrated using integrator  346  and provided to combiner  348  to cancel noise from the outgoing audio signal. Combiner  348  may receive the outgoing audio signals from the audio feed-forward path (i.e., the output of digital-to-analog converter  350 ) and may produce a corresponding audio output signal on path  352  from which noise has been cancelled. 
     If desired, noise cancellation may be implemented using other schemes. For example, noise cancellation may be implemented using a feed-forward scheme without feedback. In this type of scheme, the noise cancellation microphone for each speaker may be mounted on an external portion of the speaker housing (e.g. on the outside of an earbud). A modeling circuit may be used to model the transfer function of the earbud (e.g., to account for attenuation of high-frequency noise by the earbud material). The noise that is picked up by the external noise cancelling microphone may be passed through the modeling circuit and subtracted from the audio output (e.g., the left or right channel of audio received from device  12 ). The modeling circuit and the combining circuit that is used to subtract the noise from the output may be implemented using analog circuitry or using digital noise cancellation circuitry. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20120612
Publication Date: 20150428
Grant Date: 20150428
Priority Date: 20091119
Inventors: SANDER WENDELL B.
TERLIZZI JEFFREY J.
SANDER BRIAN
TUPMAN DAVID
CORLETT BARRY
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R2410/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/1083", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2420/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2460/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2420/09", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/6008", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/6058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2420/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/6008", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2420/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R5/033", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1083", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2420/09", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/1083", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2410/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2410/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/6058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/6008", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2460/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2460/03", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2420/09", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/6058", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 43500278