Integral Design

Posted by Marco Minerva

In this post, I’ll show how to send messages to a GHI Bluetooth module from a PC application using the 32feet .NET library.

First of all, let’s create the Gadgeteer application. Connect an USB ClientDP and an OLED Display to a FEZ Spider Mainboard, as in the following screenshot.

.NET Gadgeteer Modules in the Designer

We don’t add the Bluetooth module to the Designer because we use the beta driver implemented by Eduardo Velloso. Download the driver from CodePlex and add the Bluetooth.cs file to your project. Connect the module to socket 9. We initialize the driver in the ProgramStarted method:

bluetooth = new Bluetooth(9);
client = bluetooth.ClientMode;

bluetooth.SetDeviceName("Gadgeteer");
bluetooth.SetPinCode("1234");
bluetooth.DataReceived += new Bluetooth.DataReceivedHandler(bluetooth_DataReceived);
client.EnterPairingMode();

In this code, we set Gadgeteer as device name and we configure a PIN code. Then, in the bluetooth_DataReceived event handler, we print the received text on display:

private void bluetooth_DataReceived(Bluetooth sender, string data)
{
    oledDisplay.SimpleGraphics.ClearNoRedraw();
    oledDisplay.SimpleGraphics.DisplayText(data, Resources.GetFont(Resources.FontResources.NinaB), 
                                           GT.Color.Yellow, 0, 60);
}

The complete Program.cs file follows:

using System;
using System.Collections;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Presentation;
using Microsoft.SPOT.Presentation.Controls;
using Microsoft.SPOT.Presentation.Media;
using Microsoft.SPOT.Touch;

using Gadgeteer.Networking;
using GT = Gadgeteer;
using GTM = Gadgeteer.Modules;
using Gadgeteer.Modules.GHIElectronics;
using Gadgeteer.Modules.Seeed;
using Gadgeteer.Modules.Velloso;

namespace GadgeteerBluetooth
{
    public partial class Program
    {
        private Bluetooth bluetooth;
        private Bluetooth.Client client;

        // This method is run when the mainboard is powered up or reset.   
        void ProgramStarted()
        {
            oledDisplay.SimpleGraphics.Clear();

            bluetooth = new Bluetooth(9);
            client = bluetooth.ClientMode;

            bluetooth.SetDeviceName("Gadgeteer");
            bluetooth.SetPinCode("1234");
            bluetooth.DataReceived += new Bluetooth.DataReceivedHandler(bluetooth_DataReceived);
            client.EnterPairingMode();

            // Use Debug.Print to show messages in Visual Studio's "Output" window during debugging.
            Debug.Print("Program Started");
        }

        private void bluetooth_DataReceived(Bluetooth sender, string data)
        {
            oledDisplay.SimpleGraphics.ClearNoRedraw();
            oledDisplay.SimpleGraphics.DisplayText(data, 
                                                   Resources.GetFont(Resources.FontResources.NinaB),
                                                   GT.Color.Yellow, 0, 60);
        }
    }
}

When you run the program, Windows informs you that a device are trying to make a connection:

Connect to Bluetooth device

Click the popup and enter the PIN code to make the connection. You need to perform this task only the first time.

Now that the Gadgeteer application is up and running, and the Bluetooth module is correctly configured, we can write a PC program to control it.

Create a new WPF Application with name BluetoothControl. Write the following XAML in the MainWindow.xaml file:

<Window x:Class="BluetoothControl.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Bluetooth Control" Height="200" Width="400" ResizeMode="NoResize"
        Loaded="Window_Loaded" Closing="Window_Closing" Icon="bluetooth.png">
    <Grid Background="WhiteSmoke">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="*"></RowDefinition>
        </Grid.RowDefinitions>
        <TextBlock Grid.Row="0" Margin="10" Text="Bluetooth Control" FontWeight="Bold" FontSize="20">
        </TextBlock>
        <Grid Grid.Row="1">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"></RowDefinition>
                <RowDefinition Height="Auto"></RowDefinition>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"></ColumnDefinition>
                <ColumnDefinition Width="Auto"></ColumnDefinition>
                <ColumnDefinition Width="*"></ColumnDefinition>
            </Grid.ColumnDefinitions>
            <TextBlock Margin="10" Text="Status:" VerticalAlignment="Center" 
                       Grid.Row="0" Grid.Column="0"></TextBlock>
            <TextBlock x:Name="lblStatus" Text="No Device" Width="200" VerticalAlignment="Center" 
                       HorizontalAlignment="Left" Grid.Row="0" Grid.Column="1"></TextBlock>
            <Button Content="Search device" x:Name="btnSearchDevice" Grid.Row="0" Grid.Column="2" 
                    HorizontalAlignment="Left" VerticalAlignment="Center" Padding="5" Margin="5" 
                    Click="btnSearchDevice_Click"></Button>
            <TextBlock Margin="10" Text="Message:" VerticalAlignment="Center" Grid.Row="1"
                    Grid.Column="0"></TextBlock>
            <TextBox x:Name="txtMessage" Margin="0 0 0 0" Width="200" 
                     VerticalAlignment="Center" Grid.Row="1" Grid.Column="1"
                     HorizontalAlignment="Left"></TextBox>
            <Button Content="Send message" x:Name="btnSendMessage" VerticalAlignment="Center" 
                    Grid.Row="1" Grid.Column="2" HorizontalAlignment="Left" Margin="5" Padding="5" 
                    IsEnabled="False" Click="btnSendMessage_Click"></Button>
        </Grid>
        <TextBlock Grid.Row="3" HorizontalAlignment="Right" VerticalAlignment="Bottom" Margin="5">
            Realized by
            <Hyperlink NavigateUri="http://blogs.ugidotnet.org/marcom" 
                       RequestNavigate="Hyperlink_RequestNavigate"> 
            Marco Minerva</Hyperlink>
        </TextBlock>
    </Grid>
</Window>

The application UI will appear as in the following screenshot:

WPF Application

Then, download and add a reference to the 32feet.NET library (if you use NuGet, you can find it simply searching Bluetooth).

In the btnSearchDevice_Click event handler, we create a BackgroundWorker that executes the following code inside the DoWork event (you can refer to the downloadable project available at the end of this article for a complete reference):

try
{
    bluetooth = new BluetoothClient();
    var gadgeteerDevice = bluetooth.DiscoverDevices()
                                   .Where(d => d.DeviceName == "Gadgeteer").FirstOrDefault();
    if (gadgeteerDevice != null)
    {
        bluetooth.SetPin("1234");
        bluetooth.Connect(gadgeteerDevice.DeviceAddress, BluetoothService.SerialPort);
        bluetoothStream = bluetooth.GetStream();
        e.Result = true;
    }
    else
    {
        e.Result = false;
    }
}
catch (Exception)
{
    e.Result = false;
}

To manage bluetooth devices, we start creating a BluetoothClient object, contained in the InTheHand.Net.Sockets namespace. Then, we call the DiscoverDevices method, that returns an array of all the devices it finds. As we have called our device Gadgeteer, we use LINQ to search for a device with this name. If we find it, we set the PIN code and use the Connect method to establish a connection. It requires the device address and the Bluetooth service class to use. We must use BluetoothService.SerialPort, that identifies a service that provides a basic serial emulation connect over Bluetooth. Finally, we get the stream that allows us to communicate with the device.

In the btnSendMessage_Click event handler, if the connection has been correcly established, we can send messages over the stream:

private void btnSendMessage_Click(object sender, RoutedEventArgs e)
{
    if (bluetooth.Connected && bluetoothStream != null)
    {
        var buffer = System.Text.Encoding.UTF8.GetBytes(txtMessage.Text);
        bluetoothStream.Write(buffer, 0, buffer.Length);
        txtMessage.Text = string.Empty;
    }
}

We simply get the bytes that compose the message and then we call the Write method on the stream object: the Bluetooth module on Gadgeteer device will receive the data and show it on the diplay.

Both the Gadgeteer and the WPF application are avaiable for download.