DUE - Extensions

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Extensions are user defined functions that reside in the environment until called, they are just like any other functions in the script however these functions are provided from the TinyCLR C# side.

Defining Extensions

A static class is used to implement the extensions. Each static method in this class become available to scripts.

static class ExtensionLibrary {
    public static void ExtensionFuncSample(string arg) {
        Debug.WriteLine("Arg: " + arg);
    }

    public static int ExtensionAdder(int arg1, int arg2) {
        return arg1 + arg2;
    }        
}

Constants (const in DUE) can also be made available to the DUE system using readonly C# keyword.

static class ExtensionLibrary {
    public static void TestSample(int arg) {
        Debug.WriteLine("Arg: " + arg);
    }
    public readonly int PE11 = 75;

Any members of the extension that should not be accessed from within DUE scripts should not be made public.

Tip

Variable binding is not supported and should not be used, only use variables that are readonly.

Acessing Extensions

The DUE ScriptEngine does all the necessary magic internally. The user only needs to provide the extension class.

var script = new ScriptEngine(typeof(ExtensionLibrary));

script.Run(@"ExtensionFuncSample(""Hello DUE!"")
var x = ExtensionAdder(44, 77)
ExtensionFuncSample(""x: "" + x)
");

Example

// Non-public functions and member variables are not loaded into the script engine
static class GpioExtension {
    private static Hashtable pins = new Hashtable();
    private static GpioController gpio = GpioController.GetDefault();

    // Public static redonly member variables will be exposed as constants in the engine
    public static readonly int On = 1;
    public static readonly int Off = 0;

    // DigitalPin - Return a Pin object for the specified pin
    public static object DigitalPin(int pinNumber) {
        if (!pins.Contains(pinNumber)) {
            pins[pinNumber] = gpio.OpenPin(pinNumber);
        }
        return pins[pinNumber];
    }

    // WritePin - Write the state to the pin
    public static void WritePin(object pin, int state) {
        if (pin is GpioPin gpioPin) {
            gpioPin.SetDriveMode(GpioPinDriveMode.Output);
            gpioPin.Write(state == 0 ? GpioPinValue.Low : GpioPinValue.High);
        }
        else {
            throw new InterpreterException("Not a valid pin");
        }
    }

    // ReadPin - Read the current state of the pin
    public static int ReadPin(object pin) {
        if (pin is GpioPin gpioPin) {
            gpioPin.SetDriveMode(GpioPinDriveMode.Input);
            return gpioPin.Read() == GpioPinValue.High ? 1 : 0;
        }
        else {
            throw new InterpreterException("Not a valid pin");
        }
    }
	
	// Delay - sleep 
	public static void Delay(int ms)
	{
		Thread.Sleep(ms);
	}

}