IO (Ruggeduino)

The Ruggeduino 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).

When a single Ruggeduino is connected to your robot, you can control it using the ruggeduino object.

R.ruggeduino.something...

The serial number of each detected Ruggeduino is printed to the log when your robot starts. It will look something like this:

sr.robot3.robot INFO - Found Ruggeduino - 752303138333517171B1

If you have more than one Ruggeduino attached, the ruggeduinos object can be used to control a collection of Ruggeduinos. Similar to motors and servos, ruggeduinos is a dictionary accessed by serial number. For example, if you had a board whose serial number was “752303138333517171B1”, you could do this instead:

R.ruggeduinos["752303138333517171B1"].something...

Setting pin modes

To use one of the pins on the Ruggeduino, you must first set whether you want it to behave as an input or as an output. You can do this with the following code:

R.ruggeduino.pins[10].mode = MODE

The possible values for MODE are:

INPUT

set the pin to input mode

OUTPUT

set the pin to output mode

INPUT_PULLUP

set the pin to input mode with a pull-up resistor

An example of how to use this is below:

# set Ruggeduino pin 2 to output
R.ruggeduino.pins[2].mode = OUTPUT
# set Ruggeduino pin 3 to input
R.ruggeduino.pins[3].mode = INPUT
# set Ruggeduino pin 4 to input and enable pull-up resistor
R.ruggeduino.pins[4].mode = INPUT_PULLUP

Input

You can read a digital input pin with the following code:

# R.ruggeduinos[RUGGEDUINO_BOARD_NUMBER].pins[PIN_NO].digital_read()

# to read Ruggeduino's digital pin 3...
pin0 = R.ruggeduino.pins[3].digital_read()

pin0 will now contain True or False depending on whether the pin was high (3.3v) or low (0v), respectively.

You can read an analogue input pin with the following code:

# R.ruggeduinos[RUGGEDUINO_BOARD_NUMBER].pins[PIN_NO].analogue_read()

# to read Ruggeduino's analogue pin A0...
pin0 = R.ruggeduino.pins[A0].analogue_read()

The analogue pin numbers are available as A0, A1, A2, A3, A4, and A5 respectively.

Output

You can only set digital outputs (there’s no analogue output, although you may feel free to modify the Ruggeduino’s firmware to add the ability to output PWM if you desire). To set a digital output pin, you would use the following:

# R.ruggeduinos[RUGGEDUINO_BOARD_NUMBER].pins[PIN_NO].digital_write(VALUE)

# to set Ruggeduinos pin 2 high:
R.ruggeduino.pins[2].digital_write(True)

# to set Ruggeduino's pin 2 low:
R.ruggeduino.pins[2].digital_write(False)

Pull-up resistors

The Ruggeduino possesses the ability to enable a built-in pull-up resistor on any input pin. This takes a small amount of explanation.

Normally, input pins are not connected to anything - known as “floating”. In this state, they might read high or low, or different values depending on their environment. This is obviously not good for consistent control.

Many pieces of off-the-shelf electronics that have some form of standard I/O output will connect this pin to 3.3V (high) and 0V (low) when required, so this is not a problem. However, for simple electronics, a microswitch for example, you would normally be required to connect a resistor between the input pin and 3.3V (a pull-up resistor), or between the input pin and 0V (a pull-down resistor) to keep the input in a known state until the switch overrides it by connecting directly to the opposite state.

However, the built-in pull-up resistor alleviates this need. It essentially wires in a resistor connected to 3.3V, meaning that when this option is enabled, an input pin will “default” to being high. This means you can simply connect a switch between the input pin and a ground pin without any need of resistors - when the switch is open, the pin will read high; when closed, it will read low.