Meadow.Foundation.Leds.PwmLed

PwmLed
Status
Source code	GitHub
NuGet package

PwmLed represents an LED whose voltage (and brightness) is controlled by the duty-cycle of a PWM signal. It can be used both with Leds that have been current limited with in-series resistors, or Leds without resistors.

Controlling an LED via a PWM signal is more power efficient than using a current-limiting resistor. It also provides more control, allowing multiple grades of brightness.

To use PwmLed without a resistor, pass in the forward voltage (voltage drop) of the LED to the forwardVoltage constructor parameter, and the class will limit its output to the maximum forward voltage rating of the LED.

To use with an LED that has a resistor in series, pass 0.0 or TypicalForwardVoltage.ResistorLimited for the forwardVoltage parameter.

Code Example

PwmLedBarGraph pwmLedBarGraph;

public override Task Initialize()
{
    Resolver.Log.Info("Initializing...");

    // Using an array of Pins that support PWM (F7v2: D02-D04, D07-D13)
    IPin[] pins =
    {
        Device.Pins.D11,
        Device.Pins.D10,
        Device.Pins.D09,
        Device.Pins.D08,
        Device.Pins.D07,
        // Device.Pins.D06, // Only available for PWM on F7v1
        // Device.Pins.D05, // Only available for PWM on F7v1
        Device.Pins.D04,
        Device.Pins.D03,
        Device.Pins.D02
    };

    pwmLedBarGraph = new PwmLedBarGraph(pins, new Voltage(2.2));

    return Task.CompletedTask;
}

public override async Task Run()
{
    Resolver.Log.Info("TestLedBarGraph...");

    float percentage = 0;

    while (true)
    {
        Resolver.Log.Info("Turning them on and off for 200ms using SetLed...");
        for (int i = 0; i < pwmLedBarGraph.Count; i++)
        {
            await pwmLedBarGraph.SetLed(i, true);
            await Task.Delay(100);
            await pwmLedBarGraph.SetLed(i, false);
        }

        await Task.Delay(1000);

        Resolver.Log.Info("Turning them on using Percentage...");
        while (percentage < 1)
        {
            percentage += 0.01f;
            await pwmLedBarGraph.SetPercentage(Math.Min(1.0f, percentage));
            await Task.Delay(100);
        }

        await Task.Delay(1000);

        Resolver.Log.Info("Turning them off using Percentage...");
        while (percentage > 0)
        {
            percentage -= 0.01f;
            await pwmLedBarGraph.SetPercentage(Math.Max(0.0f, percentage));
            await Task.Delay(100);
        }

        await Task.Delay(1000);

        Resolver.Log.Info("Blinking for 5 seconds at 500ms on/off...");
        await pwmLedBarGraph.StartBlink();
        await Task.Delay(5000);
        await pwmLedBarGraph.StopAnimation();

        await Task.Delay(1000);

        Resolver.Log.Info("Bar blinking with high and low brightness for 5 seconds...");
        await pwmLedBarGraph.StartBlink(TimeSpan.FromMilliseconds(200), TimeSpan.FromMilliseconds(200), 0.75f, 0.25f);
        await Task.Delay(5000);
        await pwmLedBarGraph.StopAnimation();

        await Task.Delay(1000);

        Resolver.Log.Info("Bar pulsing for 5 seconds...");
        await pwmLedBarGraph.StartPulse();
        await Task.Delay(5000);
        await pwmLedBarGraph.StopAnimation();

        await Task.Delay(1000);

        await pwmLedBarGraph.SetBrightness(0);

        await Task.Delay(1000);
    }
}

Sample project(s) available on GitHub

Wiring Example