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  1. <h3>Summary</h3>
  2. <p>Receive audio using the built-in analog to digital converter.</p>
  3. <h3>Audio Connections</h3>
  4. <table class=doc align=center cellpadding=3>
  5. <tr class=top><th>Port</th><th>Purpose</th></tr>
  6. <tr class=odd><td align=center>Out 0</td><td>Audio Channel</td></tr>
  7. </table>
  8. <h3>Functions</h3>
  9. <p>This object has no functions to call from the Arduino sketch. It
  10. simply streams data from the ADC to its output port.</p>
  11. <h3>Hardware</h3>
  12. <p>Pin A2 is used for audio input. This circuitry is recommended.</p>
  13. <p align=center><img src="img/adccircuit.png"></p>
  14. <p>Signal range is 0 to 1.2V</p>
  15. <h3>Examples</h3>
  16. <p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; PassThroughMono
  17. </p>
  18. <p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; PeakMeterMono
  19. </p>
  20. <p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; DialTone_7segment
  21. </p>
  22. <h3>Notes</h3>
  23. <p>A different pin may be used, but adding it as an parameter
  24. to the AudioInputAnalog object definition.
  25. </p>
  26. <p>For example, to use pin A3:
  27. </p>
  28. <p class=desc><span class=keyword>AudioInputAnalog</span> adc1(<span class=literal>A3</span>);
  29. </p>
  30. <p>Noise due to high source impedance, which allows rapidly switching digital signals
  31. to capacitively couple... avoiding higher analog impedance is the solution.</p>
  32. <p>Power Supply rejection issue with simple DC bias (bigger capacitor may be needed if 3.3V has low frequency noise)</p>
  33. <p>Algorithm for automatic DC bias tracking</p>
  34. <p>TODO: actual noise measurements with different input circuitry
  35. (it's not as quiet as the audio shield)</p>