<script type="text/x-red" data-help-name="AudioEffectDelayExternal">
<h3>Summary</h3>
<div class=tooltipinfo>
<p>Delay a signal, using external memory for longer delay times! Up to 8 separate delay taps can be used.</p>
<p align=center><img src="img/delay.png"><br><small>1 kHz burst, delayed 5.2 ms.</small></p>
</div>
<h3>Audio Connections</h3>
<table class=doc align=center cellpadding=3>
<tr class=top><th>Port</th><th>Purpose</th></tr>
<tr class=odd><td align=center>In 0</td><td>Signal Input</td></tr>
<tr class=odd><td align=center>Out 0</td><td>Delay Tap #1</td></tr>
<tr class=odd><td align=center>Out 1</td><td>Delay Tap #2</td></tr>
<tr class=odd><td align=center>Out 2</td><td>Delay Tap #3</td></tr>
<tr class=odd><td align=center>Out 3</td><td>Delay Tap #4</td></tr>
<tr class=odd><td align=center>Out 4</td><td>Delay Tap #5</td></tr>
<tr class=odd><td align=center>Out 5</td><td>Delay Tap #6</td></tr>
<tr class=odd><td align=center>Out 6</td><td>Delay Tap #7</td></tr>
<tr class=odd><td align=center>Out 7</td><td>Delay Tap #8</td></tr>
</table>
<h3>Functions</h3>
<p class=func><span class=keyword>delay</span>(channel, milliseconds);</p>
<p class=desc>Set output channel (0 to 7) to delay the signals by
milliseconds. The maximum delay is approx 1.5 seconds for each 23LC1024 chip.
The actual delay
is rounded to the nearest sample. Each channel can be configured for
any delay. There is no requirement to configure the "taps" in increasing
delay order.
</p>
<p class=func><span class=keyword>disable</span>(channel);</p>
<p class=desc>Disable a channel. The output of this channel becomes
silent. If this channel is the longest delay, memory usage is
automatically reduced to accomodate only the remaining channels used.
</p>
<h3>Hardware</h3>
<p>By default, or when <span class=literal>AUDIO_MEMORY_23LC1024</span> is used (see below),
a single 23LC1024 RAM chip is used, with these pins:
<table class=doc align=center cellpadding=3>
<tr class=top><th>Pin</th><th>Signal</th></tr>
<tr class=odd><td align=center>6</td><td>CS</td></tr>
<tr class=odd><td align=center>7</td><td>MOSI</td></tr>
<tr class=odd><td align=center>12</td><td>MISO</td></tr>
<tr class=odd><td align=center>14</td><td>SCK</td></tr>
</table>
</p>
<p>When <span class=literal>AUDIO_MEMORY_MEMORYBOARD</span> is used, up to six
23LC1024 chips are used.
</p>
<p align=center><img src="img/memoryboard.jpg"><br><small><a href="https://oshpark.com/shared_projects/KZt5PaU7" target="_blank">Memoryboard 4</a></small></p>
<p>
<table class=doc align=center cellpadding=3>
<tr class=top><th>Pin</th><th>Signal</th></tr>
<tr class=odd><td align=center>2</td><td>CS0 (encoded)</td></tr>
<tr class=odd><td align=center>3</td><td>CS1 (encoded)</td></tr>
<tr class=odd><td align=center>4</td><td>CS2 (encoded)</td></tr>
<tr class=odd><td align=center>7</td><td>MOSI</td></tr>
<tr class=odd><td align=center>12</td><td>MISO</td></tr>
<tr class=odd><td align=center>14</td><td>SCK</td></tr>
</table>
</p>
<p>
If fewer than 6 chips are soldered, the optional parameter for maximum delay
must be used. See below for details. Each chip provides 1485 ms of delay
memory, so the total of all objects using AUDIO_MEMORY_MEMORYBOARD must not
exceed the amount of memory physically present.
</p>
<h3>Examples</h3>
<p>
<a href="https://www.youtube.com/watch?v=d80d1HWy5_s" target="_blank">Demo Video</a> (YouTube)
</p>
<!--
<p class=exam>File > Examples > Audio > Effects > Delay
</p>
-->
<p>
<a href="https://forum.pjrc.com/threads/29276-Limits-of-delay-effect-in-audio-library?p=79436&viewfull=1#post79436" target="_blank">Forum Conversaton</a> (with sample code)
</p>
<h3>Notes</h3>
<p>External RAM allows for longer delays without consuming
limited internal RAM. However, SPI communication is required,
which consumes much more CPU time. The
<a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html">AudioProcessorUsageMax</a>
function may be used to monitor how much CPU time is consumed.
</p>
<p>You may specify the type of hardware to be used by editing the code. AUDIO_MEMORY_23LC1024
specifies a single 23LC1024 chip. AUDIO_MEMORY_MEMORYBOARD allows using up to 6 of these
chips.
</p>
<p class=desc><span class=keyword>AudioEffectDelayExternal</span> delayExt1(<span class=literal>AUDIO_MEMORY_23LC1024</span>);
</p>
<p>You may also create more than one delay using the same hardware, where the memory is partitioned
by specifying a maximum delay in milliseconds. This can be useful if you wish to delay both
channels of a stereo signal.
<p class=desc><span class=keyword>AudioEffectDelayExternal</span> delayExt1(<span class=literal>AUDIO_MEMORY_23LC1024</span>, 700);<br><span class=keyword>AudioEffectDelayExternal</span> delayExt2(<span class=literal>AUDIO_MEMORY_23LC1024</span>, 700);
</p>
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