Make the APA102 docs available on RTD

docs/en/modules/apa102.md

@@ -1,4 +1,9 @@
 # APA102 Module
+This module provides Lua access to [APA102 RGB LEDs](https://youtu.be/UYvC-hukz-0) which are similar in function to the common [WS2812](ws2812) addressable LEDs.
+
+> DotStar LEDs are 5050-sized LEDs with an embedded micro controller inside the LED. You can set the color/brightness of each LED to 24-bit color (8 bits each red green and blue). Each LED acts like a shift register, reading incoming color data on the input pins, and then shifting the previous color data out on the output pin. By sending a long string of data, you can control an infinite number of LEDs, just tack on more or cut off unwanted LEDs at the end.
+
+source: [Adafruit](https://www.adafruit.com/products/2343)
 
 ## apa102.write()
 Send ABGR data in 8 bits to a APA102 chain.
@@ -16,16 +21,17 @@ Send ABGR data in 8 bits to a APA102 chain.
     - `G1` the first pixel's Green channel (0-255)
     - `R1` the first pixel's Red channel (0-255)
     ... You can connect a lot of APA102 ...
-    - `A1`, `G2`, `R2`, `B2` are the next APA102s Intensity, Blue, Green and channel parameters
+    - `A2`, `G2`, `R2`, `B2` are the next APA102s Intensity, Blue, Green and channel parameters
 
 #### Returns
 `nil`
 
+#### Example
 ```lua
 a = 31
 g = 0
 r = 255
 b = 0
-leds_bgr = string.char(a, g, r, b, a, g, r, b) 
+led_abgr = string.char(a, g, r, b, a, g, r, b) 
 apa102.write(2, 3, leds_abgr) -- turn two APA102s to red, connected to data_pin 2 and clock_pin 3
 ```

mkdocs.yml

@@ -31,6 +31,7 @@ pages:
     - Support: 'en/support.md'
     - Modules:
         - 'adc': 'en/modules/adc.md'
+        - 'apa102': 'en/modules/apa102.md'
         - 'bit': 'en/modules/bit.md'
         - 'bmp085': 'en/modules/bmp085.md'
         - 'cjson': 'en/modules/cjson.md'