Blink an LED

General-purpose I/O (GPIO) pins can be controlled individually. This is useful for controlling LEDs, relays, and other stateful devices. In this topic, you will use .NET and your Raspberry Pi's GPIO pins to power an LED and blink it repeatedly.

Prerequisites

  • Raspberry Pi (2 or greater) with Raspberry Pi OS installed
  • 5 mm LED
  • 330 Ω resistor
  • Breadboard
  • Jumper wires
  • Raspberry Pi GPIO breakout board (optional/recommended)
  • .NET SDK 6 or later

Ensure SSH is enabled on your Raspberry Pi. If needed, refer to Setting up an SSH Server in the Raspberry Pi documentation.

Prepare the hardware

Use the hardware components to build the circuit as depicted in the following diagram:

A Fritzing diagram showing a circuit with an LED and a resistor

The image above depicts the following connections:

  • GPIO 18 to LED anode (longer, positive lead)
  • LED cathode (shorter, negative lead) to 330 Ω resistor (either end)
  • 330 Ω resistor (other end) to ground

Refer to the following pinout diagram as needed:

A diagram showing the pinout of the Raspberry Pi GPIO header. Image courtesy Raspberry Pi Foundation.
Image courtesy Raspberry Pi Foundation.

Tip

A GPIO breakout board in conjunction with a breadboard is recommended to streamline connections to the GPIO header.

Create the app

Complete the following steps in your preferred development environment:

  1. Create a new .NET Console App using either the .NET CLI or Visual Studio. Name it BlinkTutorial.

    dotnet new console -o BlinkTutorial
    
  2. Add the Iot.Device.Bindings package to the project. Use either .NET CLI from the project directory or Visual Studio.

    dotnet add package Iot.Device.Bindings --version 2.1.0-*
    
  3. Replace the contents of Program.cs with the following code:

    using System;
    using System.Device.Gpio;
    using System.Threading;
    
    Console.WriteLine("Blinking LED. Press Ctrl+C to end.");
    int pin = 18;
    using var controller = new GpioController();
    controller.OpenPin(pin, PinMode.Output);
    bool ledOn = true;
    while (true)
    {
        controller.Write(pin, ((ledOn) ? PinValue.High : PinValue.Low));
        Thread.Sleep(1000);
        ledOn = !ledOn;
    }
    

    In the preceding code:

    • A using declaration creates an instance of GpioController. The using declaration ensures the object is disposed and hardware resources are released properly.
    • GPIO pin 18 is opened for output
    • A while loop runs indefinitely. Each iteration:
      1. Writes a value to GPIO pin 18. If ledOn is true, it writes PinValue.High (on). Otherwise, it writes PinValue.Low.
      2. Sleeps 1000 ms.
      3. Toggles the value of ledOn.
  4. Build the app. If using the .NET CLI, run dotnet build. To build in Visual Studio, press Ctrl+Shift+B.

  5. Deploy the app to the Raspberry Pi as a self-contained app. For instructions, see Deploy .NET apps to Raspberry Pi. Make sure to give the executable execute permission using chmod +x.

  6. Run the app on the Raspberry Pi by switching to the deployment directory and running the executable.

    ./BlinkTutorial
    

    The LED blinks off and on every second.

  7. Terminate the program by pressing Ctrl+C.

Congratulations! You've used GPIO to blink an LED.

Get the source code

The source for this tutorial is available on GitHub.

Next steps