【转】Android系统3.5mm耳机插口说明

【声明】

    本文转自《3.5 mm Headset Jack: Device Specification》

【正文】

3.5 mm Headset Jack: Device Specification

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

Functions

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Function	Device Support
Stereo Audio Out	Required
Audio in (Mic)	Required
Ground	Required

Software mapping

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Function	Device Support	Description
Function A control event	Required	Input event: KEY_MEDIA Android key: KEYCODE_HEADSETHOOK
Function D control event	Required	Input event: KEY_VOICECOMMAND Android key: KEYCODE_VOICE_ASSIST
Function B control event	Required	Input event: KEY_VOLUMEUP Android key: VOLUME_UP
Function C control event	Required	Input event: KEY_VOLUMEDOWN Android key: VOLUME_DOWN
Headset insertion detection	Required	Input event: SW_JACK_PHYSICAL_INSERT 7
Headset type detection	Mic	Input event: SW_MICROPHONE_INSERT 4
	No Mic	Input event: SW_HEADPHONE_INSERT 2
Headset speaker impedance	Required Headphone (low)	Failure mode is to indicate headphones so limitation would be on
	Required Line In (high)	Input event: SW_LINEOUT_INSERT 6

Mechanical

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Function	Device Support	Description
4 conductor 3.5 mm jack	Required
CTIA pinout order (LRGM)	Required	3 Pin & Mono Plug Compatible
OMTP pinout order (LRMG)	Optional but strongly recommended
Headset detect sequence	Required	Plug 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

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General

Function	Device Support	Notes
Maximum output voltage drive	150mV	>= 150mV on 32 ohm Test conditions: EN50332-2
Mic bias resistance	Required	Flexible 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 voltage	1.8V - 2.9V	To 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 Level	Device Support	Notes
70 ohm or less	Required	[Function A]
110 - 180 ohm	Required	[Function D]
210 - 290 ohm	Required	[Function B]
360 - 680 ohm	Required	[Function C]

Headset Speaker Impedance Level	Device Support	Notes
Low Threshold Detection	Required	Headphone (low) < 1 Kohm
High Threshold Detection	Required	Line In (high) > 5 Kohm

4-Segment Plug Detection Resistance (between 3rd and 4th segment)	Device Support	Notes
4-Segment Plug Threshold	Required	Resistance >= 100 ohms
3-Segment Plug Threshold	Required	Resistance < 100 ohms