Smdn.Devices.MCP2221

Smdn.Devices.MCP2221 is a .NET library for controlling MCP2221/MCP2221A USB2.0 to I²C/UART Protocol Converter with GPIO. This library enables you to control MCP2221/MCP2221A's GPIO, I²C interface, and other functionalities via USB-HID interface.

With this library, you can control I²C devices and others devices on any PCs with USB ports. It is not needed the board like the Raspberry Pi or Arduino. Also it is not required to install native device drivers on your system.

See Smdn.Devices.MCP2221 examples.

Smdn.Devices.MCP2221.GpioAdapter

Smdn.Devices.MCP2221.GpioAdapter provides the MCP2221/MCP2221A adapter interface for System.Device.Gpio. This library enables you to use the many device bindings provided by Iot.Device.Bindings.

See Smdn.Devices.MCP2221.GpioAdapter examples.

Supported MCP2221/MCP2221A features

• GP functionalities
  • GPIO
    • GPIO read/write value
    • GPIO get/set direction (some methods throw NotImplementedException)
  • ADC inputs
  • DAC outputs
  • Clock output
  • Interrupt detection
  • Other functionalities
    • Configure GP0 as SSPND
    • Configure GP0 as LED_URx
    • Configure GP1 as LED_UTx
    • Configure GP2 as USBCFG
    • Configure GP3 as LED_I2C
    • Set initial value (Negating logic level)
• I2C functionalities
  • I2C read/write (7-bit address) (Transferring larger than 60 bytes have not been tested with actual device)
  • I2C read/write (10-bit address)
  • configure communication speed
    • Standard mode (100kbps)
    • Fast mode (400kbps)
    • Low speed mode (10kbps)
    • Non-standard custom speed
• Flash/SRAM functionalities
  • SRAM read/write
    • GP settings
    • Chip settings
  • Flash read/write
    • GP Settings
    • Chip Settings
    • USB Manufacturer Descriptor String (read only)
    • USB Product Descriptor String (read only)
    • USB Serial Number Descriptor String (read only)
    • Chip Factory Serial Number (read only, always returns 01234567 (issue #8))
    • Hardware/Firmware revision (read only)
    • Passwords and chip setting protection
• Reset

Haven't tested with the actual MCP2221, but it is expected that works as same as MCP2221A.

Library API features

• Frameworks/Platforms
  • .NET Standard 2.1/.NET 5
  • Windows/Linux/MacOS and any other platforms which USB-HID driver supports
• Smdn.Devices.MCP2221
  • Read/Write and other command methods
    • Supports Span<byte>/Memory<byte>
    • Supports async, CancellationToken
    • Supports logging with ILogger, Microsoft.Extensions.Logging (example)
  • Can handle multiple MCP2221/MCP2221A by finding target with Predicate<IUsbHidDevice>
  • I2C bus scanning (example)
  • Using HIDSharp as default USB-HID driver, LibUsbDotNet also supported.
• Smdn.Devices.MCP2221.GpioAdapter
  • Provides an adapter for System.Device.Gpio
  • Can handle I2C devices using with Iot.Device.Bindings (examples)

Getting started and examples

Firstly, add package Smdn.Devices.MCP2221 to your project.

dotnet add package Smdn.Devices.MCP2221

Nextly, write your codes. The simplest code, blinking the LEDs connected to the GP pins is like below.

using System;
using System.Threading;
using Smdn.Devices.MCP2221;

using var device = MCP2221.Open();

// configure GP0-GP3 as GPIO output
device.GP0.ConfigureAsGPIO(PinMode.Output);
device.GP1.ConfigureAsGPIO(PinMode.Output);
device.GP2.ConfigureAsGPIO(PinMode.Output);
device.GP3.ConfigureAsGPIO(PinMode.Output);

// blink GP0-GP3
foreach (var gp in device.GPs) {
  Console.WriteLine($"blink {gp.PinDesignation}");

  for (var n = 0; n < 10; n++) {
    gp.SetValue(false); Thread.Sleep(100);
    gp.SetValue(true); Thread.Sleep(100);
  }
}

For detailed instructions, including wiring of the devices and parts, see blink example page.

More examples can be found in following examples directory.

• Smdn.Devices.MCP2221 examples: Small examples using MCP2221/MCP2221A functionalities.
• Smdn.Devices.MCP2221.GpioAdapter examples: Small examples using Iot.Device.Bindings.

Troubleshooting

Linux

DllImport resolving

LibUsbDotNet do DllImport-ing a shared library with the filename libusb-1.0.so.0.

If the libusb's .so filename installed on your system is different from that, use the NativeLibrary.SetDllImportResolver() to load installed .so file like below.

$ find /lib/ -name "libusb-*.so*"
/lib/x86_64-linux-gnu/libusb-1.0.so.x.y.z
/lib/i386-linux-gnu/libusb-1.0.so.x.y.z

using System.Runtime.InteropServices;

static void Main() {
  // libusb.so filename which is installed on your system
  const string fileNameLibUsb = "libusb-1.0.so.x.y.z";

  NativeLibrary.SetDllImportResolver(
    typeof(global::LibUsbDotNet.LibUsb.UsbDevice).Assembly,
    (libraryName, assembly, searchPath) => {
      if (string.Equals(libraryName, "libusb-1.0.so.0", StringComparison.OrdinalIgnoreCase)) {
        if (NativeLibrary.TryLoad(fileNameLibUsb, out var handleOfLibUsb))
          return handleOfLibUsb;
      }

      return IntPtr.Zero;
    }
  );

  // your codes here
    ︙
    ︙
}

Unbinding usbhid driver

When using LibUsbDotNet, you need to unbind the devices that are bound to the usbhid driver.

If you got the exception like below, configure the MCP2221/MCP2221A to unbind, and reconnect it again. See udev rule file for detail.

Unhandled exception. Smdn.Devices.MCP2221.DeviceUnavailableException: MCP2221/MCP2221A is not available, not privileged or disconnected.
  ---> LibUsbDotNet.LibUsb.UsbException: Resource busy
    at LibUsbDotNet.LibUsb.ErrorExtensions.ThrowOnError(Error error)
    at LibUsbDotNet.LibUsb.UsbDevice.ClaimInterface(Int32 interfaceID)

Permitting device access

If you got the exception like below, you need to run as the root user, the command like sudo dotnet run.

LibUsbDotNet:

Unhandled exception. Smdn.Devices.MCP2221.DeviceUnavailableException: MCP2221/MCP2221A is not available, not privileged or disconnected.
 ---> LibUsbDotNet.LibUsb.UsbException: Access denied (insufficient permissions)
   at LibUsbDotNet.LibUsb.ErrorExtensions.ThrowOnError(Error error)
   at LibUsbDotNet.LibUsb.UsbDevice.Open()

HIDSharp:

Unhandled exception. Smdn.Devices.MCP2221.DeviceUnavailableException: MCP2221/MCP2221A is not available, not privileged or disconnected.
 ---> HidSharp.Exceptions.DeviceIOException: Unable to open HID class device (OK).
   at HidSharp.Platform.Linux.LinuxHidStream.DeviceHandleFromPath(String path, HidDevice hidDevice, oflag oflag)
   at HidSharp.Platform.Linux.LinuxHidDevice.TryParseReportDescriptor(ReportDescriptor& parser, Byte[]& reportDescriptor)
   at HidSharp.Platform.Linux.LinuxHidDevice.RequiresGetInfo()
   at HidSharp.Platform.Linux.LinuxHidDevice.OpenDeviceDirectly(OpenConfiguration openConfig)
   at HidSharp.Device.OpenDeviceAndRestrictAccess(OpenConfiguration openConfig)
   at HidSharp.Device.Open(OpenConfiguration openConfig)
   at HidSharp.Device.Open()
   at HidSharp.HidDevice.Open()

If you want to give access privileges to a non-root user instead, you can use udev rule file. See 90-MCP2221-HIDSharp.rules or 90-MCP2221-LibUsbDotNet.rules