Electric Imp PWM Lego Train Control

class Servo extends InputPort
{
    type  = "float";
    pin = null;

    // define a constructor so that we can construct seperate instances for servos 1 and 2
    constructor(name, pin) {
        // call through to the base (InputPort) constructor with the provided name
        base.constructor(name)
        this.pin = pin
        // no need to configure the pins as we've already done it at global scope
    }

    function set(value)
    {
        // Display on our Planner node
        server.show(pin + "=" + value);

        pin.configure(PWM_OUT, 0.000870, value);
    }
}

imp.configure("PWM Test", [Servo("Channel1", hardware.pin1), Servo("Channel2", hardware.pin2)], []);

// Display our message
server.connect();
server.show("PWM Test Started!");
server.log("PWM  Test Started");

// Setup I/O
hardware.pin1.configure(PWM_OUT, 0.000870, 0.0);

hardware.pin2.configure(DIGITAL_OUT);
hardware.pin2.write(0);