Arduino API¶

The Arduino provides a total of 18 pins for either digital input or output (labelled 2 to 13 and A0 to A5), pins A0 to A5 also support analog input.

Warning

Digital pins 0 and 1 are reserved and cannot be used.

Accessing the Arduino¶

The Arduino can be accessed using the arduino property of the Robot object.

my_arduino = robot.arduino

You can use the GPIO (General Purpose Input/Output) pins for anything, from microswitches to LEDs. GPIO is only available on pins 2 to 13 and A0 to A5 because pins 0 and 1 are reserved for communication with the rest of our kit.

Pin Mode¶

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 which needs to be imported before they can be used.

from sbot import GPIOPinMode

Tip

The input modes closely resemble those of an Arduino. More information on them can be found in their docs.

Setting the pin mode¶

You will need to ensure that the pin is in the correct pin mode before performing an action with that pin. You can read about the possible pin modes below.

robot.arduino.pins[3].mode = GPIOPinMode.INPUT_PULLUP

Digital Input¶

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.

robot.arduino.pins[4].mode = GPIOPinMode.INPUT

pin_value = robot.arduino.pins[4].digital_value

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.

robot.arduino.pins[4].mode = GPIOPinMode.INPUT_PULLUP

pin_value = robot.arduino.pins[4].digital_value

Digital Output¶

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.

robot.arduino.pins[4].mode = GPIOPinMode.OUTPUT
robot.arduino.pins[6].mode = GPIOPinMode.OUTPUT

robot.arduino.pins[4].digital_value = True
robot.arduino.pins[6].digital_value = False

Analog Input¶

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

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.

from sbot import AnalogPins

robot.arduino.pins[AnalogPins.A0].mode = GPIOPinMode.INPUT

pin_value = robot.arduino.pins[AnalogPins.A0].analog_value

Tip

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. Ultrasound sensors return the distance of the closest object in mm.

# Trigger pin: 4
# Echo pin: 5

distance_mm = robot.arduino.ultrasound_measure(4, 5)

Warning

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.