index: add page on spi id

Signed-off-by: Sean Cross <sean@xobs.io>

index.html

@@ -453,6 +453,16 @@ $ dfu-util -D new-image.dfu    # Load new program</code></pre>
                 </section>
 
                 <section>
+                        <h2>Read SPI ID</h2>
+                        <pre><code class="python" data-trim>
+                                >>> spi = fomu.spi()
+                                >>> hex(spi.id())
+                                '0xc2152815'
+                                >>>
+                        </code></pre>
+                    </section>
+
+                    <section>
                     <h2>Memory-Mapped Registers</h2>
                     <pre><code class="cpp">#define CSR_VERSION_MAJOR_ADDR 0xe0007000
 #define CSR_VERSION_MINOR_ADDR 0xe0007004
@@ -464,7 +474,7 @@ $ dfu-util -D new-image.dfu    # Load new program</code></pre>
                 </section>
 
 				<section>
-					<h2>RGB LEDD reference</h2>
+					<h2>RGB LED Driver reference</h2>
 					<img data-src="img/ice40-ledd.png" alt="ICE40 LEDD registers">
 					<pre class="fragment"><code class="python" data-trim>>>> rgb.write_raw(0b0001, 255)
 >>> rgb.write_raw(0b1010, 14)