Blink an LED

Artikkel
07/31/2024

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

ARM-based (ARMv7 or greater) single-board computer (SBC)
5 mm LED
330 Ω resistor
Breadboard
Jumper wires
Raspberry Pi GPIO breakout board (optional/recommended)
.NET SDK 8 or later

Note

This tutorial is written assuming the target device is Raspberry Pi. However, this tutorial can be used for any Linux-based SBC that supports .NET, such as Orange Pi, ODROID, and more.

Ensure SSH is enabled on your device. For Raspberry Pi, 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:

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:

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:

Create a new .NET Console App using either the .NET CLI or Visual Studio. Name it BlinkTutorial.
```
dotnet new console -o BlinkTutorial
cd BlinkTutorial
```
Add the System.Device.Gpio package to the project. Use either .NET CLI from the project directory or Visual Studio.
```
dotnet add package System.Device.Gpio --version 3.2.0-*
```
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.
Build the app. If using the .NET CLI, run dotnet build. To build in Visual Studio, press Ctrl+Shift+B.
Deploy the app to the SBC 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.
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.
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

Learn how to read binary input using GPIO

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