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<section id="ad4000-driver">
<h1>AD4000 driver<a class="headerlink" href="#ad4000-driver" title="Link to this heading">¶</a></h1>
<p>Device driver for Analog Devices Inc. AD4000 series of ADCs and similar devices.</p>
<section id="supported-devices">
<h2>Supported devices<a class="headerlink" href="#supported-devices" title="Link to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference external" href="https://www.analog.com/AD4000">AD4000</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4001">AD4001</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4002">AD4002</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4003">AD4003</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4004">AD4004</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4005">AD4005</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4006">AD4006</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4007">AD4007</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4008">AD4008</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4010">AD4010</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4011">AD4011</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4020">AD4020</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4021">AD4021</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD4022">AD4022</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/ADAQ4001">ADAQ4001</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/ADAQ4003">ADAQ4003</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7685">AD7685</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7686">AD7686</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7687">AD7687</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7688">AD7688</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7690">AD7690</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7691">AD7691</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7693">AD7693</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7942">AD7942</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7946">AD7946</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7980">AD7980</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7982">AD7982</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7983">AD7983</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7984">AD7984</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7988-1">AD7988-1</a></p></li>
<li><p><a class="reference external" href="https://www.analog.com/AD7988-5">AD7988-5</a></p></li>
</ul>
<section id="wiring-connections">
<h3>Wiring connections<a class="headerlink" href="#wiring-connections" title="Link to this heading">¶</a></h3>
<p>Devices of the AD4000 series can be connected to the SPI host controller in a
few different modes.</p>
<section id="cs-mode-3-wire-turbo-mode">
<h4>CS mode, 3-wire turbo mode<a class="headerlink" href="#cs-mode-3-wire-turbo-mode" title="Link to this heading">¶</a></h4>
<p>Datasheet “3-wire” mode is what most resembles standard SPI connection which,
for these devices, comprises of connecting the controller CS line to device CNV
pin and other SPI lines as usual. This configuration is (misleadingly) called
“CS Mode, 3-Wire Turbo Mode” connection in datasheets.
NOTE: The datasheet definition of 3-wire mode for the AD4000 series is NOT the
same of standard spi-3wire mode.
This is the only connection mode that allows configuration register access but
it requires the SPI controller to support the <code class="docutils literal notranslate"><span class="pre">SPI_MOSI_IDLE_HIGH</span></code> feature.</p>
<p>Omit the <code class="docutils literal notranslate"><span class="pre">adi,sdi-pin</span></code> property in device tree to select this mode.</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span> +-------------+
+ ----------------------------------| SDO |
| | |
| +-------------------| CS |
| v | |
| +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+
</pre></div>
</div>
</section>
<section id="cs-mode-3-wire-without-busy-indicator">
<h4>CS mode, 3-wire, without busy indicator<a class="headerlink" href="#cs-mode-3-wire-without-busy-indicator" title="Link to this heading">¶</a></h4>
<p>Another wiring configuration supported as “3-wire” mode has the SDI pin
hard-wired to digital input/output interface supply (VIO). In this setup, the
controller is not required to support <code class="docutils literal notranslate"><span class="pre">SPI_MOSI_IDLE_HIGH</span></code> but register access
is not possible. This connection mode saves one wire and works with any SPI
controller.</p>
<p>Set the <code class="docutils literal notranslate"><span class="pre">adi,sdi-pin</span></code> device tree property to <code class="docutils literal notranslate"><span class="pre">"high"</span></code> to select this mode.</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span> +-------------+
+--------------------| CS |
v | |
VIO +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+
</pre></div>
</div>
<p>Alternatively, a GPIO may be connected to the device CNV pin. This is similar to
the previous wiring configuration but saves the use of a CS line.</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span> +-------------+
+--------------------| GPIO |
v | |
VIO +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+
</pre></div>
</div>
</section>
<section id="cs-mode-4-wire-without-busy-indicator">
<h4>CS mode, 4-wire without busy indicator<a class="headerlink" href="#cs-mode-4-wire-without-busy-indicator" title="Link to this heading">¶</a></h4>
<p>In datasheet “4-wire” mode, the controller CS line is connected to the ADC SDI
pin and a GPIO is connected to the ADC CNV pin. This connection mode may better
suit scenarios where multiple ADCs can share one CNV trigger.</p>
<p>Set <code class="docutils literal notranslate"><span class="pre">adi,sdi-pin</span></code> to <code class="docutils literal notranslate"><span class="pre">"cs"</span></code> to select this mode.</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span> +-------------+
+ ----------------------------------| CS |
| | |
| +-------------------| GPIO |
| v | |
| +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+
</pre></div>
</div>
</section>
</section>
</section>
<section id="iio-device-characteristics">
<h2>IIO Device characteristics<a class="headerlink" href="#iio-device-characteristics" title="Link to this heading">¶</a></h2>
<p>The AD4000 series driver supports differential and pseudo-differential ADCs.</p>
<p>The span compression feature available in AD4000 series devices can be
enabled/disabled by changing the <code class="docutils literal notranslate"><span class="pre">_scale_available</span></code> attribute of the voltage
channel. Note that span compression configuration requires writing to AD4000
configuration register, which is only possible when the ADC is wired in 3-wire
turbo mode, and the SPI controller is <code class="docutils literal notranslate"><span class="pre">SPI_MOSI_IDLE_HIGH</span></code> capable. If those
conditions are not met, no <code class="docutils literal notranslate"><span class="pre">_scale_available</span></code> attribute is provided.</p>
<p>Besides that, differential and pseudo-differential voltage channels present
slightly different sysfs interfaces.</p>
<section id="pseudo-differential-adcs">
<h3>Pseudo-differential ADCs<a class="headerlink" href="#pseudo-differential-adcs" title="Link to this heading">¶</a></h3>
<p>Typical voltage channel attributes of a pseudo-differential AD4000 series device:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>Voltage Channel Attributes</p></th>
<th class="head"><p>Description</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">in_voltage0_raw</span></code></p></td>
<td><p>Raw ADC output code.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">in_voltage0_offset</span></code></p></td>
<td><p>Offset to convert raw value to mV.</p></td>
</tr>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">in_voltage0_scale</span></code></p></td>
<td><p>Scale factor to convert raw value to mV.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">in_voltage0_scale_available</span></code></p></td>
<td><p>Toggles input span compression</p></td>
</tr>
</tbody>
</table>
</section>
<section id="differential-adcs">
<h3>Differential ADCs<a class="headerlink" href="#differential-adcs" title="Link to this heading">¶</a></h3>
<p>Typical voltage channel attributes of a differential AD4000 series device:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>Voltage Channel Attributes</p></th>
<th class="head"><p>Description</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">in_voltage0-voltage1_raw</span></code></p></td>
<td><p>Raw ADC output code.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">in_voltage0-voltage1_scale</span></code></p></td>
<td><p>Scale factor to convert raw value to mV.</p></td>
</tr>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">in_voltage0-voltage1_scale_available</span></code></p></td>
<td><p>Toggles input span compression</p></td>
</tr>
</tbody>
</table>
</section>
<section id="spi-offload-support">
<h3>SPI offload support<a class="headerlink" href="#spi-offload-support" title="Link to this heading">¶</a></h3>
<p>To be able to achieve the maximum sample rate, the driver can be used with SPI
offload engines such as the one usually present in <a class="reference external" href="http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html">AXI SPI Engine</a>, to provide
SPI offload support.</p>
<p>To keep up with SPI offloading transfer speeds, the ADC must be connected either
in 3-wire turbo mode or in 3-wire without busy indicator mode and have SPI
controller CS line connected to the CNV pin.</p>
<p>When set for SPI offload support, the IIO device will provide different
interfaces.</p>
<ul class="simple">
<li><p>Either <code class="docutils literal notranslate"><span class="pre">in_voltage0_sampling_frequency</span></code> or
<code class="docutils literal notranslate"><span class="pre">in_voltage0-voltage1_sampling_frequency</span></code> file is provided to allow setting
the sample rate.</p></li>
<li><p>IIO trigger device is not provided (no <code class="docutils literal notranslate"><span class="pre">trigger</span></code> directory).</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">timestamp</span></code> channel is not provided.</p></li>
</ul>
<p>Also, because the ADC output has a one sample latency (delay) when the device is
wired in “3-wire” mode and only one transfer per sample is done when using SPI
offloading, the first data sample in the buffer is not valid because it contains
the output of an earlier conversion result.</p>
</section>
</section>
</section>
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