| page.title=Wired audio headset specification (v1.1) |
| @jd:body |
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| <div id="qv-wrapper"> |
| <div id="qv"> |
| <h2>In this document</h2> |
| <ol id="auto-toc"> |
| </ol> |
| </div> |
| </div> |
| |
| <p>This section specifies requirements for headsets and mobile devices to |
| function uniformly across the Android ecosystem.</p> |
| |
| <h2 id="headset_accessory_plug_specifications">Headset accessory (plug) |
| specifications</h2> |
| |
| <p>The following requirements apply to headset accessories.</p> |
| |
| <h3 id="functions">Functions</h3> |
| |
| <table style="width:50%"> |
| <tr> |
| <th>Function</th> |
| <th>Accessory Support</th> |
| </tr> |
| <tr> |
| <td>Stereo Audio Out</td> |
| <td>Required</td> |
| </tr> |
| <tr> |
| <td>Audio in (Mic)</td> |
| <td>Required</td> |
| </tr> |
| <tr> |
| <td>Ground</td> |
| <td>Required</td> |
| </tr> |
| </table> |
| |
| <h3 id="control-function_mapping">Control-function mapping</h3> |
| |
| <table> |
| <tr> |
| <th style="width:33%">Control Function</th> |
| <th style="width:33%">Accessory Support</th> |
| <th style="width:33%">Description</th> |
| </tr> |
| <tr> |
| <td>Function A</td> |
| <td>Required</td> |
| <td>Play/pause/hook (Short Press), Trigger Assist (Long Press), Next |
| (Double Press)</td> |
| </tr> |
| <tr> |
| <td>Function B</td> |
| <td>Optional</td> |
| <td>Vol+</td> |
| </tr> |
| <tr> |
| <td>Function C</td> |
| <td>Optional</td> |
| <td>Vol-</td> |
| </tr> |
| <tr> |
| <td>Function D</td> |
| <td>Optional</td> |
| <td>Reserved (Nexus devices use this to launch Google voice search) |
| </td> |
| </tr> |
| </table> |
| |
| <p>Assign functions to buttons as follows:</p> |
| |
| <ul> |
| <li> All one-button headsets must implement Function A. |
| <li> Headsets with multiple buttons must implement functions according to the |
| following pattern: |
| <ul> |
| <li> 2 functions: A and D |
| <li> 3 functions: A, B, C |
| <li> 4 functions: A, B, C, D |
| </ul> |
| </ul> |
| |
| <h3 id="mechanical">Mechanical</h3> |
| |
| <table> |
| <tr> |
| <th style="width:33%">Function</th> |
| <th style="width:33%">Accessory Support</th> |
| <th style="width:33%">Notes</th> |
| </tr> |
| <tr> |
| <td>4 conductor 3.5mm plug</td> |
| <td>Required</td> |
| <td>Ref: EIAJ-RC5325A standard</td> |
| </tr> |
| <tr> |
| <td>CTIA pinout order (LRGM)</td> |
| <td>Required</td> |
| <td>Except in regions with legal requirements for OMTP pinout</td> |
| </tr> |
| <tr> |
| <td>OMTP pinout order (LRMG)</td> |
| <td>Optional</td> |
| <td></td> |
| </tr> |
| <tr> |
| <td>Microphone</td> |
| <td>Required</td> |
| <td>Must not be obstructed when operating headset controls</td> |
| </tr> |
| </table> |
| |
| <h3 id="electrical">Electrical</h3> |
| |
| <table> |
| <tr> |
| <th style="width:33%">Function</th> |
| <th style="width:33%">Accessory Support</th> |
| <th style="width:33%">Description</th> |
| </tr> |
| <tr> |
| <td>Ear speaker impedance</td> |
| <td>16 ohms or higher</td> |
| <td>Recommend 32 - 300 ohms</td> |
| </tr> |
| <tr> |
| <td>Mic DC resistance</td> |
| <td>1000 ohms or higher |
| </td> |
| <td>Mic characteristics must be compliant with section 5.4 “Audio |
| Recording” of the current |
| <a href="{@docRoot}compatibility/android-cdd.pdf">Android CDD</a></td> |
| </tr> |
| <tr> |
| <td rowspan="4">Control Function Equivalent impedance*</td> |
| <td>0 ohm</td> |
| <td>[Function A] Play/Pause/Hook</td> |
| </tr> |
| <tr> |
| <td>240 ohm +/- 1% resistance</td> |
| <td>[Function B]</td> |
| </tr> |
| <tr> |
| <td>470 ohm +/- 1% resistance</td> |
| <td>[Function C]</td> |
| </tr> |
| <tr> |
| <td>135 ohm +/- 1% resistance</td> |
| <td>[Function D]</td> |
| </tr> |
| </table> |
| |
| <p><em>*Total impedance from positive mic terminal to GND when button is |
| pressed with 2.2 V mic bias applied through 2.2 kOhm resistor</em></p> |
| |
| <p>In the following diagrams, Button A maps to Function A, Button B to |
| Function B, and so on.</p> |
| |
| <h3 id="reference_headsets">Reference headset test circuits</h3> |
| |
| <p>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.</p> |
| |
| <img src="images/headset-circuit1.png" alt="Reference Headset Test Circuit 1" /> |
| <p class="img-caption"><strong>Figure 1.</strong> Reference headset test circuit 1</p> |
| |
| <p>The following diagram for Reference Headset Test Circuit 2 shows how the |
| actual resistor values (R1 - R4) are altered to meet this specification.</p> |
| |
| <img src="images/headset-circuit2.png" alt="Reference Headset Test Circuit 2" /> |
| <p class="img-caption"><strong>Figure 2.</strong> Reference headset test circuit 2</p> |
| |
| <p>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:</p> |
| |
| <p><em>Rn=(Rmic*ReqN) / (ReqN-Rmic)</em></p> |
| |
| <p>Where R<em>n</em> is the actual resistance of a button, Req<em>N</em> is the |
| equivalent impedance value of that button (provided), and Rmic is the |
| microphone impedance value.</p> |
| |
| <p>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.</p> |
| |
| <h2 id="mobile_device_jack_specifications">Mobile device (jack) specifications</h2> |
| |
| <p class="caution"><strong>Caution:</strong> 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 <em>Analog audio ports</em> section of the <a |
| href="{@docRoot}compatibility/android-cdd.pdf">Android CDD</a>.</p> |
| |
| <h3 id="headset_jack_functions">Functions</h3> |
| |
| <table> |
| <tr> |
| <th>Function</th> |
| <th>Device Support</th> |
| </tr> |
| <tr> |
| <td>Stereo Audio Out</td> |
| <td>Required</td> |
| </tr> |
| <tr> |
| <td>Audio in (Mic)</td> |
| <td>Required</td> |
| </tr> |
| <tr> |
| <td>Ground</td> |
| <td>Required</td> |
| </tr> |
| </table> |
| |
| <h3 id="software_mapping">Software mapping</h3> |
| |
| <table> |
| <tr> |
| <th style="width:33%">Function</th> |
| <th style="width:33%">Device Support</th> |
| <th style="width:33%">Description</th> |
| </tr> |
| <tr> |
| <td>Function A control event</td> |
| <td>Required</td> |
| <td>input event KEY_MEDIA |
| <p>Android key KEYCODE_HEADSETHOOK</p></td> |
| </tr> |
| <tr> |
| <td>Function D control event</td> |
| <td>Required</td> |
| <td>input event KEY_VOICECOMMAND |
| <p>Android key KEYCODE_VOICE_ASSIST</p></td> |
| </tr> |
| <tr> |
| <td>Function B control event</td> |
| <td>Required |
| </td> |
| <td>input event KEY_VOLUMEUP |
| <p>Android key VOLUME_UP</p></td> |
| </tr> |
| <tr> |
| <td>Function C control event</td> |
| <td>Required</td> |
| <td>input event KEY_VOLUMEDOWN |
| <p>Android key VOLUME_DOWN</p></td> |
| </tr> |
| <tr> |
| <td>Headset insertion detection</td> |
| <td>Required</td> |
| <td>input event SW_JACK_PHYSICAL_INSERT 7</td> |
| </tr> |
| <tr> |
| <td rowspan="2">Headset type detection</td> |
| <td>Mic</td> |
| <td>input event SW_MICROPHONE_INSERT 4</td> |
| </tr> |
| <tr> |
| <td>No Mic</td> |
| <td>input event SW_HEADPHONE_INSERT 2</td> |
| </tr> |
| <tr> |
| <td rowspan="2">Headset speaker impedance</td> |
| <td>Required Headphone (low)</td> |
| <td>Failure mode is to indicate headphones so limitation would be on</td> |
| </tr> |
| <tr> |
| <td>Required Line In (high)</td> |
| <td>input event SW_LINEOUT_INSERT 6</td> |
| </tr> |
| </table> |
| |
| <h3 id="mechanical11">Mechanical</h3> |
| |
| <table> |
| <tr> |
| <th style="width:33%">Function</th> |
| <th style="width:33%">Device Support</th> |
| <th style="width:33%">Description</th> |
| </tr> |
| <tr> |
| <td>4 conductor 3.5mm jack</td> |
| <td>Required</td> |
| <td></td> |
| </tr> |
| <tr> |
| <td>CTIA pinout order (LRGM)</td> |
| <td>Required</td> |
| <td>3 Pin & Mono Plug Compatible</td> |
| </tr> |
| <tr> |
| <td>OMTP pinout order (LRMG)</td> |
| <td>Optional but strongly recommended</td> |
| <td></td> |
| </tr> |
| <tr> |
| <td>Headset detect sequence</td> |
| <td>Required</td> |
| <td>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.</td> |
| </tr> |
| </table> |
| |
| <h3 id="electrical12">Electrical</h3> |
| |
| <h4 id="general">General</h4> |
| |
| <table> |
| <tr> |
| <th style="width:33%">Function</th> |
| <th style="width:33%">Device Support</th> |
| <th style="width:33%">Notes</th> |
| </tr> |
| <tr> |
| <td>Maximum output voltage drive</td> |
| <td>150mV</td> |
| <td>>= 150mV on 32 ohm |
| <p>Test conditions: EN50332-2</p></td> |
| </tr> |
| <tr> |
| <td>Mic bias resistance</td> |
| <td>Required</td> |
| <td>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</td> |
| </tr> |
| <tr> |
| <td>Mic bias voltage</td> |
| <td>1.8V - 2.9V</td> |
| <td>To guarantee compatibility to common microphone capsules.</td> |
| </tr> |
| </table> |
| |
| <h4 id="function_impedance_and_threshold_detection">Function impedance and |
| threshold detection</h4> |
| |
| <p>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.</p> |
| |
| <table> |
| <tr> |
| <th style="width:40%">Button Impedance Level</th> |
| <th style="width:20%">Device Support</th> |
| <th style="width:40%">Notes</th> |
| </tr> |
| <tr> |
| <td>70 ohm or less</td> |
| <td>Required</td> |
| <td>[Function A]</td> |
| </tr> |
| <tr> |
| <td>110 - 180 ohm</td> |
| <td>Required</td> |
| <td>[Function D]</td> |
| </tr> |
| <tr> |
| <td>210 - 290 ohm</td> |
| <td>Required</td> |
| <td>[Function B]</td> |
| </tr> |
| <tr> |
| <td>360 - 680 ohm</td> |
| <td>Required</td> |
| <td>[Function C]</td> |
| </tr> |
| </table> |
| |
| <table> |
| <tr> |
| <th style="width:40%">Headset Speaker Impedance Level</th> |
| <th style="width:20%">Device Support</th> |
| <th style="width:40%">Notes</th> |
| </tr> |
| <tr> |
| <td>Low Threshold Detection</td> |
| <td>Required</td> |
| <td>Headphone (low) < 1 Kohm</td> |
| </tr> |
| <tr> |
| <td>High Threshold Detection</td> |
| <td>Required</td> |
| <td>Line In (high) > 5 Kohm</td> |
| </tr> |
| </table> |