General Purpose Input/Output (GPIO) pins are fundamental for interacting with the physical world in embedded systems. Windows IoT provides a robust and accessible API for managing GPIO, enabling developers to connect sensors, actuators, and other hardware peripherals to their devices.

Understanding GPIO Pins

GPIO pins can be configured as either an input or an output.

  • Input: Reads the state of an external signal (e.g., a button press, sensor reading).
  • Output: Controls an external device by setting the pin to a high (on) or low (off) voltage level (e.g., turning on an LED, activating a relay).
Each GPIO pin on a device has a unique number that can be used to access it programmatically.

Getting Started with GPIO in Windows IoT

The primary way to interact with GPIO in Windows IoT is through the Windows.Devices.Gpio namespace. Here's a basic C# example demonstrating how to open a GPIO pin, set it as an output, and toggle an LED:


using Windows.Devices.Gpio;
using System.Threading.Tasks;

public sealed class GpioControllerExample
{
    private GpioPin ledPin;
    private const int LED_PIN_NUMBER = 5; // Example GPIO pin number

    public async Task InitializeGpioAsync()
    {
        var gpioController = await GpioController.GetDefaultAsync();
        if (gpioController == null)
        {
            // Handle error: no GPIO controller found
            return;
        }

        ledPin = gpioController.OpenPin(LED_PIN_NUMBER);
        ledPin.SetDriveMode(GpioPinDriveMode.Output);
        ledPin.Write(GpioPinValue.Low); // Start with LED off
    }

    public void ToggleLed()
    {
        if (ledPin != null)
        {
            ledPin.Write(ledPin.Read() == GpioPinValue.Low ? GpioPinValue.High : GpioPinValue.Low);
        }
    }

    public void CleanupGpio()
    {
        if (ledPin != null)
        {
            ledPin.Dispose();
            ledPin = null;
        }
    }
}

Common Use Cases

  • LED Control: Simple visual indicators for device status.
  • Button Input: Reading user input or detecting events.
  • Sensor Integration: Connecting digital sensors like accelerometers, temperature sensors, or motion detectors.
  • Actuator Control: Driving motors, relays, or buzzers.

Important Considerations

  • Pin Numbering: Refer to your specific device's documentation for the correct GPIO pin mapping.
  • Voltage Levels: Ensure compatibility between your hardware and the device's GPIO voltage levels (typically 3.3V or 5V). Use level shifters if necessary.
  • Resource Management: Always close or dispose of GPIO pins when they are no longer needed to free up system resources.
  • Error Handling: Implement robust error handling for cases where the GPIO controller is not available or pins cannot be opened.

Advanced Topics

  • Interrupts: Efficiently respond to hardware events without constant polling.
  • PWM (Pulse Width Modulation): Control the brightness of LEDs or the speed of motors.
  • I2C and SPI: Communicate with more complex peripherals using dedicated protocols.
Explore the Windows IoT documentation for detailed guides on these advanced features.