Microsoft Learn

Serial Peripheral Interface (SPI) Development on Windows IoT

This guide provides comprehensive information and best practices for developing with the Serial Peripheral Interface (SPI) on Windows IoT. SPI is a synchronous serial communication interface specification used for short-distance communication, primarily in embedded systems.

Understanding SPI

SPI is a full-duplex communication protocol that uses a master-slave architecture. A single master device can communicate with multiple slave devices. The communication uses at least four wires:

• MOSI (Master Out Slave In): Data line from the master to the slave.
• MISO (Master In Slave Out): Data line from the slave to the master.
• SCLK (Serial Clock): Clock signal generated by the master.
• CS/SS (Chip Select/Slave Select): A line used by the master to select a specific slave device.

Windows IoT provides APIs to interact with SPI devices, allowing you to connect and communicate with various peripherals like sensors, displays, and memory chips.

Getting Started with SPI

To begin developing with SPI on Windows IoT, you'll typically need to:

1. Enable SPI: Ensure the SPI interface is enabled in your device's hardware configuration or BIOS settings.
2. Connect Hardware: Wire your SPI device to the correct pins on your Windows IoT device. Consult your device's documentation for pinouts.
3. Install Drivers: Make sure the appropriate SPI controller drivers are installed and functional.
4. Use Windows IoT APIs: Utilize the Windows.Devices.Spi namespace in your UWP or IoT Enterprise application.

Core Concepts and Usage

The Windows.Devices.Spi namespace offers classes like SpiDevice to manage SPI communication.

Initializing an SPI Device

You'll need to specify the controller name, device ID (chip select number), and connection settings (mode, clock speed, data bits).

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

// ...

public async Task InitializeSpiDeviceAsync()
{
    string spiControllerName = "SPI0"; // Example: Replace with your actual controller name
    int chipSelectNumber = 0; // Example: Replace with your actual chip select number

    try
    {
        // Get the SPI controller
        var controller = await SpiController.GetDefaultAsync(); // Or specify controller name if multiple

        if (controller == null)
        {
            Console.WriteLine("SPI controller not found.");
            return;
        }

        // Configure the SPI connection settings
        var settings = new SpiConnectionSettings(chipSelectNumber);
        settings.Mode = SpiMode.Mode0; // Example: SPI Mode 0
        settings.ClockFrequency = 1000000; // 1 MHz Example
        settings.DataBitLength = 8; // 8 bits per transfer

        // Create an SPI device
        SpiDevice spiDevice = await SpiDevice.FromIdAsync(controller.DeviceId, settings);

        if (spiDevice == null)
        {
            Console.WriteLine("SPI device not found or could not be opened.");
            return;
        }

        Console.WriteLine($"SPI device initialized successfully on {spiControllerName}.");
        // Now you can use spiDevice for communication
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error initializing SPI device: {ex.Message}");
    }
}
                

Performing Data Transfers

The SpiDevice class provides methods for sending and receiving data, such as Write, Read, and TransferFullDuplex.

// Example of writing data
byte[] writeBuffer = { 0x01, 0x02, 0x03 };
spiDevice.Write(writeBuffer);

// Example of reading data
byte[] readBuffer = new byte[5]; // Buffer to store read data
spiDevice.Read(readBuffer);

// Example of full-duplex transfer
byte[] writeBufferFullDuplex = { 0xA0 };
byte[] readBufferFullDuplex = new byte[1];
spiDevice.TransferFullDuplex(writeBufferFullDuplex, readBufferFullDuplex);
                

Common SPI Peripherals

• Sensors: Accelerometers, gyroscopes, temperature sensors (e.g., MPU6050, BMP280).
• Displays: OLED, LCD screens (e.g., SSD1306, ST7735).
• Memory: EEPROMs, flash memory chips.
• Analog-to-Digital Converters (ADCs) / Digital-to-Analog Converters (DACs).

Troubleshooting Tips

• Double-check wiring connections (MOSI, MISO, SCLK, CS).
• Verify the SPI mode (0, 1, 2, or 3) matches your device's requirements.
• Ensure the clock frequency is within the supported range for both the master and slave.
• Confirm the SPI controller is correctly enabled and recognized by the OS.
• Check for any conflicting device drivers or configurations.