How to read data from Serial Ports on Android using MAUI

Question

Hi everyone,

I'm working on a .NET MAUI app for Android and I’m having some trouble. Right now, my code just displays the connected USB devices info, but I actually need to read data from serial ports instead.

Here's the code I have so far:

#if ANDROID
using Android.Content;
using Android.Hardware.Usb;
#endif

namespace MauiApp2
{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
        }

        private void OnCounterClicked(object sender, EventArgs e)
        {
#if ANDROID
            var act = Platform.CurrentActivity;
            UsbManager manager = (UsbManager)act.GetSystemService(Context.UsbService);
            IDictionary<string, UsbDevice> devicesDictionary = manager.DeviceList;

            if (devicesDictionary != null && devicesDictionary.Count > 0)
            {
                string devicesInfo = "Available USB Devices:\n";
                foreach (var device in devicesDictionary.Values)
                {
                    devicesInfo += $"Device Name: {device.DeviceName}, Vendor ID: {device.VendorId}, Product ID: {device.ProductId}\n";
                }
                DisplayAlert("USB Devices", devicesInfo, "OK");
            }
            else
            {
                DisplayAlert("USB Devices", "No USB devices available.", "OK");
            }
#endif
        }
    }
}

The code shows the connected USB devices, but I need to be able to read incoming data from a serial port (like ), not just show device info./dev/ttyUSB0

So my questions are:

How can I initialize and read data from a Serial Port using .NET MAUI on Android?

I’d really appreciate any help or even just a code example on how to read from a serial port in an Android MAUI app.

Thanks a lot in advance!

Answer 1

Hello,

You can read data from the UsbEndpoint using use UsbDeviceConnection.bulkTransfer. This method is blocking, please use it in a thread.

Then you can open the device using UsbManager and UsbDeviceConnection. Then read it.

UsbInterface usbInterface = device.getInterface(0);  // Get the interface of the device
  UsbEndpoint endpointIn = usbInterface.GetEndpoint(0); // Assuming the first endpoint is IN
  UsbDeviceConnection connection = UsbManager.OpenDevice(device); // Open connection
 
  if (connection != null && connection.ClaimInterface(usbInterface, true))
  {
      // Connection successful
 
      int TIMEOUT = 1000;  // Timeout for reading
      byte[] buffer = new byte[64];  // Buffer for reading data
      int readBytes = connection.BulkTransfer(endpointIn, buffer, buffer.Length, TIMEOUT);
 
      if (readBytes > 0)
      {
          Java.Lang.String data = new Java.Lang.String(buffer, 0, readBytes);
          Log.Debug("USB", "Read data: " + data.ToString());
      }
  }

Best Regards,

Leon Lu

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Answer 2

If you are writing an Android app, why use Maui? Why not just make it an Android-only app using either <TargetFramework>net9.0-android35</TargetFramework> or <TargetFramework>net8-android</TargetFramework>? That way, you only need to follow Android's documentation. What sort of device are you trying to connect to?

Answer 3

In .NET MAUI for Android, you can use the Android Hardware APIs to work with serial ports since .NET MAUI itself doesn't have direct serial port support.

Here’s a brief approach:

1. Use Android Java APIs (UsbManager and UsbDevice) to access the serial ports.
2. Implement serial communication using the UsbSerial for Android library or other external libraries.
3. Call these Android-specific APIs in your MAUI app using platform-specific code.

You'd need to write platform-specific code under the Platforms/Android folder to handle this.