1page.title=Wired audio headset specification 2@jd:body 3 4<!-- 5 Copyright 2014 The Android Open Source Project 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18--> 19<div id="qv-wrapper"> 20 <div id="qv"> 21 <h2>In this document</h2> 22 <ol id="auto-toc"> 23 </ol> 24 </div> 25</div> 26 27<p><em>Version 1.1</em></p> 28 29<p>This document specifies the requirements for headsets and mobile devices to 30function uniformly across the Android ecosystem. It is separated into two 31sections beginning with the specifications for the headset 32accessory followed by the specifications for the mobile device.</p> 33 34<h2 id=headset_accessory_plug_specifications>Headset Accessory (Plug) Specifications</h2> 35 36<p>The requirements in the following section apply to the headset accessory.</p> 37 38<h3 id=functions>Functions</h3> 39 40<table> 41 <tr> 42 <th> 43<p><strong>Function</strong></p> 44</th> 45 <th> 46<p><strong>Accessory Support</strong></p> 47</th> 48 </tr> 49 <tr> 50 <td> 51<p>Stereo Audio Out</p> 52</td> 53 <td> 54<p><strong>Required</strong></p> 55</td> 56 </tr> 57 <tr> 58 <td> 59<p>Audio in (Mic)</p> 60</td> 61 <td> 62<p><strong>Required</strong></p> 63</td> 64 </tr> 65 <tr> 66 <td> 67<p>Ground</p> 68</td> 69 <td> 70<p><strong>Required</strong></p> 71</td> 72 </tr> 73</table> 74 75<h3 id=control-function_mapping>Control-Function Mapping</h3> 76 77<table> 78 <tr> 79 <th> 80<p><strong>Control Function</strong></p> 81</th> 82 <th> 83<p><strong>Accessory Support</strong></p> 84</th> 85 <th> 86<p><strong>Description</strong></p> 87</th> 88 </tr> 89 <tr> 90 <td> 91<p>Function A</p> 92</td> 93 <td> 94<p><strong>Required</strong></p> 95</td> 96 <td> 97<p>Play/pause/hook (Short Press), Trigger Assist (Long Press), Next (double press)</p> 98</td> 99 </tr> 100 <tr> 101 <td> 102<p>Function B</p> 103</td> 104 <td> 105<p>Optional</p> 106</td> 107 <td> 108<p>Vol+</p> 109</td> 110 </tr> 111 <tr> 112 <td> 113<p>Function C</p> 114</td> 115 <td> 116<p>Optional</p> 117</td> 118 <td> 119<p>Vol-</p> 120</td> 121 </tr> 122 <tr> 123 <td> 124<p>Function D</p> 125</td> 126 <td> 127<p>Optional</p> 128</td> 129 <td> 130<p>Reserved (Nexus devices will use this reserved function to launch Google 131voice search)</p> 132</td> 133 </tr> 134</table> 135 136<p><strong>Assign functions to buttons as follows</strong>:</p> 137 138<ul> 139 <li> All one-button headsets must implement Function A. 140 <li> Headsets with multiple buttons must implement functions according to the 141following pattern: 142 <ul> 143 <li> 2 functions: A and D 144 <li> 3 functions: A, B, C 145 <li> 4 functions: A, B, C, D 146 </ul> 147</ul> 148 149<h3 id=mechanical>Mechanical</h3> 150 151<table> 152 <tr> 153 <th> 154<p><strong>Function</strong></p> 155</th> 156 <th> 157<p><strong>Accessory Support</strong></p> 158</th> 159 <th> 160<p><strong>Notes</strong></p> 161</th> 162 </tr> 163 <tr> 164 <td> 165<p>4 conductor 3.5mm plug</p> 166</td> 167 <td> 168<p><strong>Required</strong></p> 169</td> 170 <td> 171<p>Ref: EIAJ-RC5325A standard</p> 172</td> 173 </tr> 174 <tr> 175 <td> 176<p>CTIA pinout order (LRGM)</p> 177</td> 178 <td> 179<p><strong>Required</strong></p> 180</td> 181 <td> 182<p>Except in regions with legal requirements for OMTP pinout</p> 183</td> 184 </tr> 185 <tr> 186 <td> 187<p>OMTP pinout order (LRMG)</p> 188</td> 189 <td> 190<p>Optional</p> 191</td> 192 <td></td> 193 </tr> 194 <tr> 195 <td> 196<p>Microphone</p> 197</td> 198 <td> 199<p><strong>Required</strong></p> 200</td> 201 <td> 202<p>Must not be obstructed when operating headset controls</p> 203</td> 204 </tr> 205</table> 206 207<h3 id=electrical>Electrical</h3> 208 209<table> 210 <tr> 211 <th> 212<p><strong>Function</strong></p> 213</th> 214 <th> 215<p><strong>Accessory Support</strong></p> 216</th> 217 <th> 218<p><strong>Description</strong></p> 219</th> 220 </tr> 221 <tr> 222 <td> 223<p>Ear speaker impedance</p> 224</td> 225 <td> 226<p><strong>16 ohms or higher</strong></p> 227</td> 228 <td> 229<p>Recommend 32 - 300 ohms</p> 230</td> 231 </tr> 232 <tr> 233 <td> 234<p>Mic DC resistance</p> 235</td> 236 <td> 237<p><strong>1000 ohms or higher</strong></p> 238</td> 239 <td> 240<p>Mic characteristics must be compliant with section 5.4 “Audio Recording” of 241current Android Compatibility Definition Document (CDD)</p> 242</td> 243 </tr> 244 <tr> 245 <td> 246<p>Control Function Equivalent impedance*</p> 247 248<p>*Total impedance from positive mic terminal to GND when button is pressed with 2492.2 V mic bias applied through 2.2 kOhm resistor</p> 250</td> 251 <td> 252<p><strong>0 ohm</strong></p> 253</td> 254 <td> 255<p>[Function A] Play/Pause/Hook</p> 256</td> 257 </tr> 258 <tr> 259 <td></td> 260 <td> 261<p><strong>240 ohm</strong> +/- 1% resistance</p> 262</td> 263 <td> 264<p>[Function B]</p> 265</td> 266 </tr> 267 <tr> 268 <td></td> 269 <td> 270<p><strong>470 ohm</strong> +/- 1% resistance</p> 271</td> 272 <td> 273<p>[Function C] </p> 274</td> 275 </tr> 276 <tr> 277 <td></td> 278 <td> 279<p><strong>135 ohm</strong> +/- 1% resistance</p> 280</td> 281 <td> 282<p>[Function D]</p> 283</td> 284 </tr> 285</table> 286 287<p>In the following diagrams, Button A is mapped to Function A, Button B to 288Function B, and so on.</p> 289 290<h3 id=reference_headset_test_circuit_1>Reference Headset Test Circuit 1</h3> 291 292<img src="images/headset-circuit1.png" alt="Reference Headset Test Circuit 1" /> 293<p class="img-caption"><strong>Figure 1.</strong> Reference headset test circuit 1</p> 294 295<p class="note"><strong>Note:</strong> The above diagram shows the CTIA pinout 296for a 4-segment plug. For the OMTP pinout, switch the positions of the MIC and 297GND segments.</p> 298 299<h3 id=reference_headset_test_circuit_2>Reference Headset Test Circuit 2</h3> 300 301<p>The second reference circuit shows how the actual resistor values (R1 - R4) 302are altered to meet this specification.</p> 303 304<img src="images/headset-circuit2.png" alt="Reference Headset Test Circuit 2" /> 305<p class="img-caption"><strong>Figure 2.</strong> Reference headset test circuit 2</p> 306 307<p>The actual resistance of the buttons parallel with the microphone (R1-R4) is 308based on the microphone capsule resistance (Rmic) and the equivalent impedance 309values (ReqA-ReqD). Use the following formula:</p> 310 311<p><em>Rn=(Rmic*ReqN) / (ReqN-Rmic)</em></p> 312 313<p>Where R<em>n</em> is the actual resistance of a button, Req<em>N</em> is the 314equivalent impedance value of that button (provided), and Rmic is the 315microphone impedance value.</p> 316 317<p>The example above assumes a 5 kohm microphone impedance (Rmic). Therefore, to 318achieve an equivalent R4 impedance of 135 ohm (ReqD), the actual resistor value 319(R4) needs to be 139 ohms.</p> 320 321 322<h2 id=mobile_device_jack_specifications>Mobile Device (Jack) Specifications</h2> 323 324<p class="caution"><strong>Caution:</strong> To achieve compatibility with the 325headset specification above, devices that include a 4 conductor 3.5mm audio 326jack must meet the following specifications. Please see the <em>Analog audio 327ports</em> section of the <a 328href="{@docRoot}compatibility/android-cdd.pdf">Android Compatibility Definition 329Document (CDD)</a> for Android compatibility requirements.</p> 330 331<p><strong>Headset Jack Functions</strong></p> 332<table> 333 <tr> 334 <th> 335<p><strong>Function</strong></p> 336</th> 337 <th> 338<p><strong>Device Support</strong></p> 339</th> 340 </tr> 341 <tr> 342 <td> 343<p>Stereo Audio Out</p> 344</td> 345 <td> 346<p><strong>Required</strong></p> 347</td> 348 </tr> 349 <tr> 350 <td> 351<p>Audio in (Mic)</p> 352</td> 353 <td> 354<p><strong>Required</strong></p> 355</td> 356 </tr> 357 <tr> 358 <td> 359<p>Ground</p> 360</td> 361 <td> 362<p><strong>Required</strong></p> 363</td> 364 </tr> 365</table> 366 367<h3 id=software_mapping>Software mapping</h3> 368 369<table> 370 <tr> 371 <th> 372<p><strong>Function</strong></p> 373</th> 374 <th> 375<p><strong>Device Support</strong></p> 376</th> 377 <th> 378<p><strong>Description</strong></p> 379</th> 380 </tr> 381 <tr> 382 <td> 383<p>Function A control event </p> 384</td> 385 <td> 386<p><strong>Required</strong></p> 387</td> 388 <td> 389<p>input event KEY_MEDIA</p> 390 391<p>Android key KEYCODE_HEADSETHOOK</p> 392</td> 393 </tr> 394 <tr> 395 <td> 396<p>Function D control event</p> 397</td> 398 <td> 399<p><strong>Required</strong></p> 400</td> 401 <td> 402<p>input event KEY_VOICECOMMAND</p> 403 404<p>Android key KEYCODE_VOICE_ASSIST</p> 405</td> 406 </tr> 407 <tr> 408 <td> 409<p>Function B control event</p> 410</td> 411 <td> 412<p><strong>Required</strong></p> 413</td> 414 <td> 415<p>input event KEY_VOLUMEUP</p> 416 417<p>Android key VOLUME_UP</p> 418</td> 419 </tr> 420 <tr> 421 <td> 422<p>Function C control event</p> 423</td> 424 <td> 425<p><strong>Required</strong></p> 426</td> 427 <td> 428<p>input event KEY_VOLUMEDOWN</p> 429 430<p>Android key VOLUME_DOWN</p> 431</td> 432 </tr> 433 <tr> 434 <td> 435<p>Headset insertion detection</p> 436</td> 437 <td> 438<p><strong>Required</strong></p> 439</td> 440 <td> 441<p>input event SW_JACK_PHYSICAL_INSERT 7</p> 442</td> 443 </tr> 444 <tr> 445 <td> 446<p>Headset type detection</p> 447</td> 448 <td> 449<p><strong>Mic</strong></p> 450</td> 451 <td> 452<p>input event SW_MICROPHONE_INSERT 4</p> 453</td> 454 </tr> 455 <tr> 456 <td> 457<p>Headset type detection</p> 458</td> 459 <td> 460<p><strong>No Mic</strong></p> 461</td> 462 <td> 463<p>input event SW_HEADPHONE_INSERT 2</p> 464</td> 465 </tr> 466 <tr> 467 <td> 468<p>Headset speaker impedance</p> 469</td> 470 <td> 471<p><strong>Required Headphone (low)</strong></p> 472</td> 473 <td> 474<p>Failure mode is to indicate headphones so that limitation would be on</p> 475</td> 476 </tr> 477 <tr> 478 <td> 479<p>Headset speaker impedance</p> 480</td> 481 <td> 482<p><strong>Required Line In (high)</strong></p> 483</td> 484 <td> 485<p>input event SW_LINEOUT_INSERT 6</p> 486</td> 487 </tr> 488</table> 489 490<h3 id=mechanical11>Mechanical</h3> 491 492<table> 493 <tr> 494 <th> 495<p><strong>Function</strong></p> 496</th> 497 <th> 498<p><strong>Device Support</strong></p> 499</th> 500 <th> 501<p><strong>Description</strong></p> 502</th> 503 </tr> 504 <tr> 505 <td> 506<p>4 conductor 3.5mm jack</p> 507</td> 508 <td> 509<p><strong>Required</strong></p> 510</td> 511 <td></td> 512 </tr> 513 <tr> 514 <td> 515<p>CTIA pinout order (LRGM)</p> 516</td> 517 <td> 518<p><strong>Required</strong></p> 519</td> 520 <td> 521<p>3 Pin & Mono Plug Compatible</p> 522</td> 523 </tr> 524 <tr> 525 <td> 526<p>OMTP pinout order (LRMG)</p> 527</td> 528 <td> 529<p>Optional but <strong>Strongly Recommended</strong></p> 530</td> 531 <td></td> 532 </tr> 533 <tr> 534 <td> 535<p>Headset detect sequence</p> 536</td> 537 <td> 538<p><strong>Required</strong></p> 539</td> 540 <td> 541<p>Plug insert notification must only be triggered after all contacts on plug are 542touching their relevant segments. This will prevent unreliable headset 543detection due to slow insertion. </p> 544</td> 545 </tr> 546</table> 547 548<h3 id=electrical12>Electrical</h3> 549 550<h4 id=general>General</h4> 551 552<table> 553 <tr> 554 <th> 555<p><strong>Function</strong></p> 556</th> 557 <th> 558<p><strong>Device Support</strong></p> 559</th> 560 <th> 561<p><strong>Notes</strong></p> 562</th> 563 </tr> 564 <tr> 565 <td> 566<p>Maximum output voltage drive</p> 567</td> 568 <td> 569<p>150mV </p> 570</td> 571 <td> 572<p>>= 150mV on 32 ohm</p> 573 574<p>Test conditions: EN50332-2</p> 575</td> 576 </tr> 577 <tr> 578 <td> 579<p>Mic bias resistance </p> 580</td> 581 <td> 582<p>Required</p> 583</td> 584 <td> 585<p>Flexible on detection method used and microphone bias resistor selection. 586Require that all button resistance value ranges specified below be detected and 587related to their respective function</p> 588</td> 589 </tr> 590 <tr> 591 <td> 592<p>Mic bias voltage</p> 593</td> 594 <td> 595<p>1.8V - 2.9V</p> 596</td> 597 <td> 598<p>To guarantee compatibility to common microphone capsules.</p> 599</td> 600 </tr> 601</table> 602 603<h4 id=function_impedance_and_threshold_detection>Function Impedance and Threshold Detection</h4> 604 605<p>Devices must detect the following resistor ladder on the accessories. The 606accessories will be tested to the standardized circuit diagram in the diagram 607illustrated earlier (Reference Headset Test Circuit) where the total impedance 608is measured from MIC terminal to GND when a button is pressed with 2.2V mic 609bias applied through 2.2 kOhm resistor. This is the same effective resistance 610as the button detection circuit with the microphone in parallel with the button 611resistor.</p> 612<table> 613 <tr> 614 <th> 615<p><strong>Button Impedance Level</strong></p> 616</th> 617 <th> 618<p><strong>Device Support</strong></p> 619</th> 620 <th> 621<p><strong>Notes</strong></p> 622</th> 623 </tr> 624 <tr> 625 <td> 626<p><strong>70 ohm or less</strong></p> 627</td> 628 <td> 629<p><strong>Required</strong></p> 630</td> 631 <td> 632<p>[Function A]</p> 633</td> 634 </tr> 635 <tr> 636 <td> 637<p><strong>110 - 180 ohm </strong></p> 638</td> 639 <td> 640<p><strong>Required</strong></p> 641</td> 642 <td> 643<p>[Function D]</p> 644</td> 645 </tr> 646 <tr> 647 <td> 648<p><strong>210 - 290 ohm</strong></p> 649</td> 650 <td> 651<p><strong>Required</strong></p> 652</td> 653 <td> 654<p>[Function B]</p> 655</td> 656 </tr> 657 <tr> 658 <td> 659<p><strong>360 - 680 ohm </strong></p> 660</td> 661 <td> 662<p><strong>Required</strong></p> 663</td> 664 <td> 665<p>[Function C]</p> 666</td> 667 </tr> 668 <tr> 669 <td> 670<p><strong>Headset speaker impedance level</strong></p> 671</td> 672 <td></td> 673 <td></td> 674 </tr> 675 <tr> 676 <td> 677<p>Low Threshold Detection</p> 678</td> 679 <td> 680<p><strong>Required</strong></p> 681</td> 682 <td> 683<p>Headphone (low) < 1 Kohm</p> 684</td> 685 </tr> 686 <tr> 687 <td> 688<p>High Threshold Detection</p> 689</td> 690 <td> 691<p><strong>Required</strong></p> 692</td> 693 <td> 694<p>Line In (high) > 5 Kohm</p> 695</td> 696 </tr> 697</table> 698
