1page.title=Testing Circuit 2@jd:body 3 4<div id="qv-wrapper"> 5 <div id="qv"> 6 <h2>In this document</h2> 7 <ol id="auto-toc"> 8 </ol> 9 </div> 10</div> 11 12<p> 13The file <a href="http://developer.android.com/downloads/partner/audio/av_sync_board.zip">av_sync_board.zip</a> 14contains CAD files for an A/V sync and latency testing 15printed circuit board (PCB). 16The files include a fabrication drawing, EAGLE CAD, schematic, and BOM. 17</p> 18 19<p> 20This PCB 21can be used to help measure the time between flashing the device's 22notification LED or screen backlight, vs. detecting an audio signal. 23When combined with a dual-channel oscilloscope and suitable test app, 24it can show the difference in time between detecting the light and audio. 25That assumes the LED or backlight response time and light detector's response time 26are negligible relative to the audio. 27</p> 28 29<p> 30This design is supplied "as is", and we aren't be responsible for any errors in the design. 31But if you have any suggestions for improvement, please post to android-porting group. 32</p> 33 34<p> 35Of course, this is not the only (or necessarily best) way to measure A/V sync and latency, 36and we would like to hear about your alternative methods, also at android-porting group. 37</p> 38 39<p> 40There are currently no compatibility requirements to use this particular PCB. 41We supply it to encourage your continued attention to audio performance. 42</p> 43 44<h2 id="images">Images</h2> 45 46<p> 47These photos show the circuit in action. 48</p> 49 50<img style="margin:1.5em auto" src="images/breadboard.jpg" alt="breadboard prototype" /> 51<br /> 52<center>Breadboard prototype</center> 53 54<img style="margin:1.5em auto" src="images/pcb.jpg" alt="an early run of the PCB" /> 55<br /> 56<center>An early run of the PCB</center> 57 58<img style="margin:1.5em auto" src="images/display.jpg" alt="example display"> 59<br /> 60<center>Example display</center> 61<p> 62This image 63shows the scope display for an unspecified device, software release, and test conditions; 64the results are not typical and cannot be used to extrapolate to other situations. 65</p> 66 67<h2 id="video">Video</h2> 68 69<p> 70This <a href="http://www.youtube.com/watch?v=f95S2IILBJY">Youtube video</a> 71shows the the breadboard version testing circuit in operation. 72Skip ahead to 1:00 to see the circuit. 73</p> 74 75
