Rewrite arduino page to align with sbot

docs/programming/arduino.md

@@ -2,7 +2,7 @@
 
 The [Arduino](https://store.arduino.cc/arduino-uno-rev3) provides a
 total of 18 pins for either digital input or output (labelled 2 to 13
-and A0 to A5), including 6 for analogue input (labelled A0 to A5).
+and A0 to A5), pins A0 to A5 also support analog input.
 
 !!! warning
     Digital pins 0 and 1 are reserved and cannot be used.
@@ -23,7 +23,7 @@ rest of our kit.
 
 ## Pin Mode
 
-GPIO pins have four different modes. A pin can only have one mode at a
+GPIO pins have different modes. A pin can only have one mode at a
 time, and some pins aren't compatible with certain modes. These pin
 modes are represented by an
 [enum](https://docs.python.org/3/library/enum.html) which needs to be
@@ -34,7 +34,8 @@ from sbot import GPIOPinMode
 ```
 
 !!! tip
-    The input modes closely resemble those of an Arduino. More information on them can be found in [their docs](https://www.arduino.cc/en/Tutorial/DigitalPins).
+    The input modes closely resemble those of an Arduino.
+    More information on them can be found in [their docs](https://www.arduino.cc/en/Tutorial/DigitalPins).
 
 ### Setting the pin mode
 
@@ -43,77 +44,76 @@ performing an action with that pin. You can read about the possible pin
 modes below.
 
 ``` python
-robot.arduino.pins[3].mode = GPIOPinMode.DIGITAL_INPUT_PULLUP
+robot.arduino.pins[3].mode = GPIOPinMode.INPUT_PULLUP
 ```
 
-### `GPIOPinMode.DIGITAL_INPUT`
+### Digital Input
 
-In this mode, the digital state of the pin (whether it is high or low)
-can be read.
+Digital inputs can be used to check the state of a pin (whether it is high or low).
+This is useful for connecting something such as a micro-switch.
 
 ``` python
-robot.arduino.pins[4].mode = GPIOPinMode.DIGITAL_INPUT
+robot.arduino.pins[4].mode = GPIOPinMode.INPUT
 
-pin_value = robot.arduino.pins[4].digital_state
+pin_value = robot.arduino.pins[4].digital_value
 ```
 
-### `GPIOPinMode.DIGITAL_INPUT_PULLUP`
-
-Same as `GPIOPinMode.DIGITAL_INPUT`, but with an internal [pull-up
-resistor](https://learn.sparkfun.com/tutorials/pull-up-resistors)
-enabled.
+Some external switches may require a pull up resistor.
+`GPIOPinMode.INPUT_PULLUP`, is the same as `INPUT` but also enables an internal [pull-up
+resistor](https://learn.sparkfun.com/tutorials/pull-up-resistors).
 
 ``` python
-robot.arduino.pins[4].mode = GPIOPinMode.DIGITAL_INPUT_PULLUP
+robot.arduino.pins[4].mode = GPIOPinMode.INPUT_PULLUP
 
-pin_value = robot.arduino.pins[4].digital_state
+pin_value = robot.arduino.pins[4].digital_value
 ```
 
-### `GPIOPinMode.DIGITAL_OUTPUT`
+### Digital Output
 
-In this mode, we can set binary values of `0V` or `5V` to the pin.
+Digital outputs can be used to set binary values of `0V` or `5V` to the pin.
+This can be used to turn an LED on and off for example.
 
 ``` python
-robot.arduino.pins[4].mode = GPIOPinMode.DIGITAL_OUTPUT
-robot.arduino.pins[6].mode = GPIOPinMode.DIGITAL_OUTPUT
+robot.arduino.pins[4].mode = GPIOPinMode.OUTPUT
+robot.arduino.pins[6].mode = GPIOPinMode.OUTPUT
 
-robot.arduino.pins[4].digital_state = True
-robot.arduino.pins[6].digital_state = False
+robot.arduino.pins[4].digital_value = True
+robot.arduino.pins[6].digital_value = False
 ```
 
-### `GPIOPinMode.ANALOGUE_INPUT`
+### Analog Input
 
-Certain sensors output analogue signals rather than digital ones, and so
-have to be read differently. The Arduino has six analogue inputs, which
-are labelled `A0` to `A5`; however pins `A4` and `A5` are reserved and
-cannot be used.
+Certain sensors output analog signals rather than digital ones, and so
+have to be read differently. The Arduino has six analog inputs, which
+are labelled `A0` to `A5`.
 
 !!! tip
-    Analogue signals can have any voltage, while digital signals can only
-    take on one of two voltages. You can read more about digital vs analogue
+    Analog signals can have any voltage, while digital signals can only
+    take on one of two voltages. You can read more about digital vs analog
     signals [here](https://learn.sparkfun.com/tutorials/analog-vs-digital).
 
 ``` python
-from sbot import AnaloguePin
+from sbot import AnalogPins
 
-robot.arduino.pins[AnaloguePin.A0].mode = GPIOPinMode.ANALOGUE_INPUT
+robot.arduino.pins[AnalogPins.A0].mode = GPIOPinMode.INPUT
 
-pin_value = robot.arduino.pins[AnaloguePin.A0].analogue_value
+pin_value = robot.arduino.pins[AnalogPins.A0].analog_value
 ```
 
 !!! tip
-    The values are the voltages read on the pins, between 0 and 5.
+    The values are the voltages read on the pin, between 0 and 5.
 
 ## Ultrasound Sensors
 
-You can also measure distance using an ultrasound sensor from the arduino.
+You can also measure distance using an ultrasound sensor from the arduino. Ultrasound sensors return the distance of the closest object in mm.
 
 ```python
 # Trigger pin: 4
 # Echo pin: 5
 
-distance_metres = robot.arduino.ultrasound_measure(4, 5)
+distance_mm = robot.arduino.ultrasound_measure(4, 5)
 ```
 
 !!! warning
-    The ultrasound sensor can measure distances up to 2 metres. If the ultrasound signal has to travel further than 2m, the sensor will timeout and return `None`.
+    The ultrasound sensor can measure distances up to 4 metres. 
+    If the ultrasound signal has to travel further than 4m, the sensor will timeout and return 0.