<div dir="ltr">Looked up that Python library wrapper for the SPI interface. Here is the c file that does all the work.<div><br><div><a href="https://github.com/adafruit/adafruit-beaglebone-io-python/blob/master/source/spimodule.c">https://github.com/adafruit/adafruit-beaglebone-io-python/blob/master/source/spimodule.c</a><br>
</div></div><div><br></div><div>Line 710 sets the variable path</div><div><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">if</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">(</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">snprintf</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">(</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">path</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">,</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">MAXPATH</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">,</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(221,17,68);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">"/dev/spidev%d.%d"</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">,</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">bus</span><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">+</span><span class="" style="color:rgb(0,153,153);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">1</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">,</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">device</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">)</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">>=</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">MAXPATH</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">)</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">{</span></div>
<div>Line 715 opens device for read/write</div><div><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">if</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">((</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">self</span><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">-></span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">fd</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">=</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">open</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">(</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">path</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">,</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">O_RDWR</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">,</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(0,153,153);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">0</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">))</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">==</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="font-weight:bold;color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">-</span><span class="" style="color:rgb(0,153,153);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">1</span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">)</span><span style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre"> </span><span class="" style="color:rgb(51,51,51);font-family:Consolas,'Liberation Mono',Courier,monospace;font-size:12px;line-height:18px;white-space:pre">{</span></div>
<div><br></div><div>So from what I gather,</div><div>/dev/spidev2.3</div><div>2 would be which spi interface you are using ( guessing there is only one, so it should probably be 1 ).</div><div>3 would be the device would would like to fiddle with (e.g. my LCD or LED character display also would probably be 1).</div>
<div><br></div><div>After that I don't know but here is a good place to start.</div><div><a href="https://www.kernel.org/doc/Documentation/spi/spidev">https://www.kernel.org/doc/Documentation/spi/spidev</a><br></div><div>
<br></div><div>-Morio</div></div>