1page.title=Testing Circuit
2@jd:body
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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>
28The file <a href="http://developer.android.com/downloads/partner/audio/av_sync_board.zip">av_sync_board.zip</a>
29contains CAD files for an A/V sync and latency testing
30printed circuit board (PCB).
31The files include a fabrication drawing, EAGLE CAD, schematic, and BOM. See <a
32href="audio_latency.html">Audio Latency</a> for recommended testing methods.
33</p>
34
35<p>
36This PCB
37can be used to help measure the time between flashing the device's
38notification LED or screen backlight, vs. detecting an audio signal.
39When combined with a dual-channel oscilloscope and suitable test app,
40it can show the difference in time between detecting the light and audio.
41That assumes the LED or backlight response time and light detector's response time
42are negligible relative to the audio.
43</p>
44
45<p>
46This design is supplied "as is", and we aren't be responsible for any errors in the design.
47But if you have any suggestions for improvement, please post to the <a
48href="https://groups.google.com/forum/#!forum/android-porting">android-porting</a> group.
49</p>
50
51<p>
52Of course, this is not the only (or necessarily best) way to measure A/V sync and latency,
53and we would like to hear about your alternative methods, also at android-porting group.
54</p>
55
56<p>
57There are currently no compatibility requirements to use this particular PCB.
58We supply it to encourage your continued attention to audio performance.
59</p>
60
61<h2 id="images">Images</h2>
62
63<p>
64These photos show the circuit in action.
65</p>
66
67<img style="margin:1.5em auto" src="images/breadboard.jpg" alt="breadboard prototype" />
68<br />
69<center>Breadboard prototype</center>
70
71<img style="margin:1.5em auto" src="images/pcb.jpg" alt="an early run of the PCB" />
72<br />
73<center>An early run of the PCB</center>
74
75<img style="margin:1.5em auto" src="images/display.jpg" alt="example display">
76<br />
77<center>Example display</center>
78<p>
79This image
80shows the scope display for an unspecified device, software release, and test conditions;
81the results are not typical and cannot be used to extrapolate to other situations.
82</p>
83
84<h2 id="video">Video</h2>
85
86<p>
87This <a href="http://www.youtube.com/watch?v=f95S2IILBJY">Youtube video</a>
88shows the the breadboard version testing circuit in operation.
89Skip ahead to 1:00 to see the circuit.
90</p>
91
92