Raspberry Pi Docs

Author: trickeydan

docs/source/_static/kit/arduino_pinout.png

@@ -21,6 +21,35 @@ The reset button allows you to instantly reboot the Arduino in case it
 isn’t working. This is not a guaranteed fix, but may solve some
 problems.
 
+GPIO Pins
+---------
+
+The Arduino allows you to connect your kit to your own electronics. It has fourteen digital I/O pins, and six analogue. The analogue pins can read an analogue signal from 0 to 5V. The board also has a couple of ground pins, as well as some pins fixed at 3.3V and 5V output.
+
+The pin layout of the servo assembly is the same as an Arduino Uno.
+
+.. figure:: /_static/kit/arduino_pinout.png
+   :alt: Pin Map
+   :scale: 20%
+
+   Pin Map
+
+Ultrasound Sensors
+------------------
+
+Ultrasound sensors are a useful way of measuring distance. Ultrasound sensors communicate with the kit using two wires. A signal is sent to the sensor on the trigger pin, and the length of a response pulse on the echo pin can be used to calculate the distance.
+
+.. Warning:: Ultrasound should only be considered accurate up to around two metres, beyond which the signal can become distorted and produce erroneous results.
+
+The sensor has four pin connections: ground, 5V (sometimes labelled
+*vcc*), *trigger* and *echo*. Most ultrasound sensors will label which
+pin is which. The ground and 5V should be wired to the ground and 5V
+pins of the Arduino respectively. The trigger and echo pins should be
+attached to two different digital IO pins. Take note of these two pins,
+you’ll need them to use the sensor.
+
+.. Hint:: If the sensor always returns a distance of zero, it means the *trigger* and *echo* pins are connected the wrong way! Either change the pin numbers in the code, or swap the connections.
+
 Designs
 -------