Wired Audio Headset Specification (v1.1)

本文详细介绍了Android设备与其有线音频耳机配件之间的交互规范。包括耳机插头的要求、按钮功能分配、机械与电气特性等,并对手机端接口进行了规定。

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来自: http://source.android.com/devices/accessories/headset/specification.html

 

Wired Audio Headset Specification (v1.1)

 

This section specifies requirements for headsets and mobile devices to function uniformly across the Android ecosystem.

Headset accessory (plug) specifications


The following requirements apply to headset accessories.

Functions

FunctionAccessory Support
Stereo Audio OutRequired
Audio in (Mic)Required
GroundRequired

Control-function mapping

Control FunctionAccessory SupportDescription
Function ARequiredPlay/pause/hook (Short Press), Trigger Assist (Long Press), Next (Double Press)
Function BOptionalVol+
Function COptionalVol-
Function DOptionalReserved (Nexus devices use this to launch Voice Assist)

Assign functions to buttons as follows:

  • All one-button headsets must implement Function A.
  • Headsets with multiple buttons must implement functions according to the following pattern:
    • 2 functions: A and D
    • 3 functions: A, B, C
    • 4 functions: A, B, C, D

Mechanical

FunctionAccessory SupportNotes
4 conductor 3.5mm plugRequiredRef: EIAJ-RC5325A standard
CTIA pinout order (LRGM)RequiredExcept in regions with legal requirements for OMTP pinout
OMTP pinout order (LRMG)Optional 
MicrophoneRequiredMust not be obstructed when operating headset controls

Electrical

FunctionAccessory SupportDescription
Ear speaker impedance16 ohms or higherRecommend 32 - 300 ohms
Mic DC resistance1000 ohms or higherMic characteristics must be compliant with section 5.4 “Audio Recording” of the current Android CDD
Control Function Equivalent impedance*0 ohm[Function A] Play/Pause/Hook
240 ohm +/- 1% resistance[Function B]
470 ohm +/- 1% resistance[Function C]
135 ohm +/- 1% resistance[Function D]

*Total impedance from positive mic terminal to GND when button is pressed with 2.2 V mic bias applied through 2.2 kOhm resistor

In the following diagrams, Button A maps to Function A, Button B to Function B, and so on.

Reference headset test circuits

The following diagram for Reference Headset Test Circuit 1 shows the CTIA pinout for a 4-segment plug. For the OMTP pinout, switch the positions of the MIC and GND segments.

Reference Headset Test Circuit 1

Figure 1. Reference headset test circuit 1

The following diagram for Reference Headset Test Circuit 2 shows how the actual resistor values (R1 - R4) are altered to meet this specification.

Reference Headset Test Circuit 2

Figure 2. Reference headset test circuit 2

The actual resistance of the buttons parallel with the microphone (R1-R4) is based on the microphone capsule resistance (Rmic) and the equivalent impedance values (ReqA-ReqD). Use the following formula:

Rn=(Rmic*ReqN) / (Rmic+ReqN)

Where Rn is the actual resistance of a button, ReqN is the equivalent impedance value of that button (provided), and Rmic is the microphone impedance value.

The example above assumes a 5 kohm microphone impedance (Rmic); to achieve an equivalent R4 impedance of 135 ohm (ReqD), the actual resistor value (R4) must be 139 ohms.

Mobile device (jack) specifications


Caution: To achieve compatibility with the headset specification, devices that include a 4 conductor 3.5mm audio jack must meet the following specifications. For Android compatibility requirements, refer to the Analog audio ports section of the Android CDD.

Functions

FunctionDevice Support
Stereo Audio OutRequired
Audio in (Mic)Required
GroundRequired

Software mapping

FunctionDevice SupportDescription
Function A control eventRequiredinput event KEY_MEDIA

Android key KEYCODE_HEADSETHOOK

Function D control eventRequiredinput event KEY_VOICECOMMAND

Android key KEYCODE_VOICE_ASSIST

Function B control eventRequiredinput event KEY_VOLUMEUP

Android key VOLUME_UP

Function C control eventRequiredinput event KEY_VOLUMEDOWN

Android key VOLUME_DOWN

Headset insertion detectionRequiredinput event SW_JACK_PHYSICAL_INSERT 7
Headset type detectionMicinput event SW_MICROPHONE_INSERT 4
No Micinput event SW_HEADPHONE_INSERT 2
Headset speaker impedanceRequired Headphone (low)Failure mode is to indicate headphones so limitation would be on
Required Line In (high)input event SW_LINEOUT_INSERT 6

Mechanical

FunctionDevice SupportDescription
4 conductor 3.5mm jackRequired 
CTIA pinout order (LRGM)Required3 Pin & Mono Plug Compatible
OMTP pinout order (LRMG)Optional but strongly recommended 
Headset detect sequenceRequiredPlug insert notification must be triggered only after all contacts on plug are touching their relevant segments (this prevents unreliable headset detection due to slow insertion.

Electrical

General
FunctionDevice SupportNotes
Maximum output voltage drive150mV>= 150mV on 32 ohm

Test conditions: EN50332-2

Mic bias resistanceRequiredFlexible on detection method used and microphone bias resistor selection. Require that all button resistance value ranges specified below be detected and related to their respective function
Mic bias voltage1.8V - 2.9VTo guarantee compatibility to common microphone capsules.
Function impedance and threshold detection

Devices must detect the following resistor ladder on the accessories. The accessories will be tested to the standardized circuit diagram in the diagram illustrated earlier (Reference Headset Test Circuit) where the total impedance is measured from MIC terminal to GND when a button is pressed with 2.2V mic bias applied through 2.2 kOhm resistor. This is the same effective resistance as the button detection circuit with the microphone in parallel with the button resistor.

Button Impedance LevelDevice SupportNotes
70 ohm or lessRequired[Function A]
110 - 180 ohmRequired[Function D]
210 - 290 ohmRequired[Function B]
360 - 680 ohmRequired[Function C]
Headset Speaker Impedance LevelDevice SupportNotes
Low Threshold DetectionRequiredHeadphone (low) < 1 Kohm
High Threshold DetectionRequiredLine In (high) > 5 Kohm
4-Segment Plug Detection Resistance (between 3rd and 4th segment)Device SupportNotes
4-Segment Plug ThresholdRequiredResistance >= 100 ohms
3-Segment Plug ThresholdRequiredResistance < 100 ohms
代码的意思是把AUDIO_DEVICE_LIST_DEF(V)替换为 AUDIO_DEVICE_LIST_UNIQUE_DEF(V) \ V(AUDIO_DEVICE_OUT_AUX_DIGITAL, AUDIO_DEVICE_OUT_HDMI) \ V(AUDIO_DEVICE_OUT_STUB, AUDIO_DEVICE_OUT_DEFAULT) \ V(AUDIO_DEVICE_IN_VOICE_CALL, AUDIO_DEVICE_IN_TELEPHONY_RX) \ V(AUDIO_DEVICE_IN_AUX_DIGITAL, AUDIO_DEVICE_IN_HDMI) \ V(AUDIO_DEVICE_IN_STUB, AUDIO_DEVICE_IN_DEFAULT) 其中#define AUDIO_DEVICE_LIST_UNIQUE_DEF(V) \ V(AUDIO_DEVICE_NONE, 0x0u) \ V(AUDIO_DEVICE_OUT_EARPIECE, 0x1u) \ V(AUDIO_DEVICE_OUT_SPEAKER, 0x2u) \ V(AUDIO_DEVICE_OUT_WIRED_HEADSET, 0x4u) \ V(AUDIO_DEVICE_OUT_WIRED_HEADPHONE, 0x8u) \ V(AUDIO_DEVICE_OUT_BLUETOOTH_SCO, 0x10u) \ V(AUDIO_DEVICE_OUT_BLUETOOTH_SCO_HEADSET, 0x20u) \ V(AUDIO_DEVICE_OUT_BLUETOOTH_SCO_CARKIT, 0x40u) \ V(AUDIO_DEVICE_OUT_BLUETOOTH_A2DP, 0x80u) \ V(AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES, 0x100u) \ V(AUDIO_DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER, 0x200u) \ V(AUDIO_DEVICE_OUT_HDMI, 0x400u) \ V(AUDIO_DEVICE_OUT_ANLG_DOCK_HEADSET, 0x800u) \ V(AUDIO_DEVICE_OUT_DGTL_DOCK_HEADSET, 0x1000u) \ V(AUDIO_DEVICE_OUT_USB_ACCESSORY, 0x2000u) \ V(AUDIO_DEVICE_OUT_USB_DEVICE, 0x4000u) \ V(AUDIO_DEVICE_OUT_REMOTE_SUBMIX, 0x8000u) \ V(AUDIO_DEVICE_OUT_TELEPHONY_TX, 0x10000u) \ V(AUDIO_DEVICE_OUT_LINE, 0x20000u) \ V(AUDIO_DEVICE_OUT_HDMI_ARC, 0x40000u) \ V(AUDIO_DEVICE_OUT_HDMI_EARC, 0x40001u) \ V(AUDIO_DEVICE_OUT_SPDIF, 0x80000u) \ V(AUDIO_DEVICE_OUT_FM, 0x100000u) \ V(AUDIO_DEVICE_OUT_AUX_LINE, 0x200000u) \ V(AUDIO_DEVICE_OUT_SPEAKER_SAFE, 0x400000u) \ V(AUDIO_DEVICE_OUT_IP, 0x800000u) \ V(AUDIO_DEVICE_OUT_BUS, 0x1000000u) \ V(AUDIO_DEVICE_OUT_PROXY, 0x2000000u) \ V(AUDIO_DEVICE_OUT_USB_HEADSET, 0x4000000u) \ V(AUDIO_DEVICE_OUT_HEARING_AID, 0x8000000u) \ V(AUDIO_DEVICE_OUT_ECHO_CANCELLER, 0x10000000u) \ V(AUDIO_DEVICE_OUT_BLE_HEADSET, 0x20000000u) \ V(AUDIO_DEVICE_OUT_BLE_SPEAKER, 0x20000001u) \ V(AUDIO_DEVICE_OUT_BLE_BROADCAST, 0x20000002u) \ V(AUDIO_DEVICE_OUT_DEFAULT, AUDIO_DEVICE_BIT_DEFAULT) \ V(AUDIO_DEVICE_IN_COMMUNICATION, AUDIO_DEVICE_BIT_IN | 0x1u) \ V(AUDIO_DEVICE_IN_AMBIENT, AUDIO_DEVICE_BIT_IN | 0x2u) \ V(AUDIO_DEVICE_IN_BUILTIN_MIC, AUDIO_DEVICE_BIT_IN | 0x4u) \ V(AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET, AUDIO_DEVICE_BIT_IN | 0x8u) \ V(AUDIO_DEVICE_IN_WIRED_HEADSET, AUDIO_DEVICE_BIT_IN | 0x10u) \ V(AUDIO_DEVICE_IN_HDMI, AUDIO_DEVICE_BIT_IN | 0x20u) \ V(AUDIO_DEVICE_IN_TELEPHONY_RX, AUDIO_DEVICE_BIT_IN | 0x40u) \ V(AUDIO_DEVICE_IN_BACK_MIC, AUDIO_DEVICE_BIT_IN | 0x80u) \ V(AUDIO_DEVICE_IN_REMOTE_SUBMIX, AUDIO_DEVICE_BIT_IN | 0x100u) \ V(AUDIO_DEVICE_IN_ANLG_DOCK_HEADSET, AUDIO_DEVICE_BIT_IN | 0x200u) \ V(AUDIO_DEVICE_IN_DGTL_DOCK_HEADSET, AUDIO_DEVICE_BIT_IN | 0x400u) \ V(AUDIO_DEVICE_IN_USB_ACCESSORY, AUDIO_DEVICE_BIT_IN | 0x800u) \ V(AUDIO_DEVICE_IN_USB_DEVICE, AUDIO_DEVICE_BIT_IN | 0x1000u) \ V(AUDIO_DEVICE_IN_FM_TUNER, AUDIO_DEVICE_BIT_IN | 0x2000u) \ V(AUDIO_DEVICE_IN_TV_TUNER, AUDIO_DEVICE_BIT_IN | 0x4000u) \ V(AUDIO_DEVICE_IN_LINE, AUDIO_DEVICE_BIT_IN | 0x8000u) \ V(AUDIO_DEVICE_IN_SPDIF, AUDIO_DEVICE_BIT_IN | 0x10000u) \ V(AUDIO_DEVICE_IN_BLUETOOTH_A2DP, AUDIO_DEVICE_BIT_IN | 0x20000u) \ V(AUDIO_DEVICE_IN_LOOPBACK, AUDIO_DEVICE_BIT_IN | 0x40000u) \ V(AUDIO_DEVICE_IN_IP, AUDIO_DEVICE_BIT_IN | 0x80000u) \ V(AUDIO_DEVICE_IN_BUS, AUDIO_DEVICE_BIT_IN | 0x100000u) \ V(AUDIO_DEVICE_IN_PROXY, AUDIO_DEVICE_BIT_IN | 0x1000000u) \ V(AUDIO_DEVICE_IN_USB_HEADSET, AUDIO_DEVICE_BIT_IN | 0x2000000u) \ V(AUDIO_DEVICE_IN_BLUETOOTH_BLE, AUDIO_DEVICE_BIT_IN | 0x4000000u) \ V(AUDIO_DEVICE_IN_HDMI_ARC, AUDIO_DEVICE_BIT_IN | 0x8000000u) \ V(AUDIO_DEVICE_IN_HDMI_EARC, AUDIO_DEVICE_BIT_IN | 0x8000001u) \ V(AUDIO_DEVICE_IN_ECHO_REFERENCE, AUDIO_DEVICE_BIT_IN | 0x10000000u) \ V(AUDIO_DEVICE_IN_BLE_HEADSET, AUDIO_DEVICE_BIT_IN | 0x20000000u) \ V(AUDIO_DEVICE_IN_DEFAULT, AUDIO_DEVICE_BIT_IN | AUDIO_DEVICE_BIT_DEFAULT)
07-05
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