Merge pull request #4 from insektionen/development

Adding RPi explanation

src/lights/roof_led/index.md

@@ -1,13 +1,12 @@
 # Roof LED
 
-Kistan has a grid of pixels in the roof controlled by a single controller. The
-pixels are connected together using wires, and divided to three different power
-supply groups. All the power supplies have their common connected to eliminate
-some interference.
+Kistan has a grid of pixels on the roof controlled by a single controller. The
+pixels are connected using wires and divided into three different power supply
+groups (see [power drawing][1]).
 
 ## Addressing
 
-Each pixel is represented as a fixture in the LMixer and have 3 channels.
+Each pixel is represented as a fixture in the LMixer and has 3 channels.
 Addressing is linear and can be followed like a snake back and forth in the
 roof. See the picture below for exact fixture IDs.
 
@@ -19,4 +18,34 @@ All roof LEDs are controlled by a single controller. It is connected to the same
 network as the servers and LMixer is streaming the layer data over the network
 using UDP.
 
-[roof_indexing]: ./images/roof_indexing.png "The addressing for roof LEDs"
+## Raspberry Pi
+
+A Raspberry Pi with custom software is used to control the roof LEDs. It is
+powered with a normal USB Power supply and is connected to the internet with a
+LAN cable.
+
+![rpi_image]
+
+The black wire is connected to ground on pin number 4 (GND)
+
+The green wire is connected to data on pin number 12 (GPIO18)
+
+![rpi_connection]
+
+### Location of Pi
+
+The Pi is located on top of the cable tray in the roof. As indicated on this
+picture.
+
+![rpi_location]
+
+
+[1]: ../../drawings/roof_led
+
+[roof_indexing]: ./images/roof_indexing.png "The addressing for roof LEDs"
+
+[rpi_image]: ./images/RPI_image.jpg "Image of the installed Pi"
+
+[rpi_connection]: ./images/RPI_GPIO_Pinout_marked.png "The pinout of the Raspberry Pi 3b+"
+
+[rpi_location]: ./images/RPI_location.png "The pinout of the Raspberry Pi 3b+"