Bluetooth Device Development using C#

anilkr — Sat, 13 Sep 2008 02:28:55 GMT

As they say Necessity is mother of invention, I recently got a Jabra BT3030 Bluetooth headset. I paired it to my Windows Mobile phone. When I wanted to turn on the Bluetooth, I had to go to wireless manager and turn it on. I am a little bit lazy and had an idea why not map a button on the phone to toggle the bluetooh radio. But, this is not possible by default, so started working on a program to map to the button.

Fortunately it is very simple to interact with Bluetooth radio and devices on the phone using Windows Embedded Source Tools for Bluetooth Technology. This download contains bunch of C# files which you can directly use in your code. You will get classes such as BluetoothDevice and BluetoothRadio which allow you to control the device and paired devices.

   1: using System;

   2: using System.Collections.Generic;

   3: using System.Text;

   4: using Microsoft.WindowsMobile.SharedSource.Bluetooth;

5:

   6: namespace ToggleBluetooth

   7: {

   8:     class Program

   9:     {

  10:         static void Main(string[] args)

  11:         {

  12:             BluetoothRadio brad = new BluetoothRadio();

  13:             if (brad.BluetoothRadioMode == BluetoothRadioMode.Off)

  14:                 brad.BluetoothRadioMode = BluetoothRadioMode.On;

  15:             else

  16:                 brad.BluetoothRadioMode = BluetoothRadioMode.Off;

  17:         }

  18:     }

  19: }

After that, I added a setup project and made sure that a shortcut for the application is under Programs folder, so that I can map it using the Buttons applet of Settings panel. After the install on the device, you should be able to see the program in the "Assign a program" list.

As usual, here are some links and blog post.

Windows Embedded Source Tools for Bluetooth Technology - http://msdn.microsoft.com/en-us/embedded/aa714533.aspx
Channel 9 Wiki (has a good Q&A) - http://channel9.msdn.com/wiki/bluetoothdevelopment/
MSDN Code Samples page - http://msdn.microsoft.com/en-us/library/bb158662.aspx

Thanks
Anil RV

Volume Control using Phidgets Sensors

anilkr — Fri, 11 Jul 2008 21:38:00 GMT

Phidgets.com offers USB sensors which can be controlled by .NET. They also offer the interface kit with which you can use the sensor. You can get variety of sensors like vibration, light, IR, voltage, temperature, PH, rotation etc. For this blog entry I have bought a Phidget Interface kit with LCD attachment. This kit has 8 digital input/output and 8 analog sensors and with 2 line LCD attachment as display.

Phidgets.com provides the .NET assemblies to control the interface kit and to read the input from the attached sensors. I have always wanted a physical volume control for my laptop which is missing, I have to either use windows volume control or function keys to control the volume. The rotation sensor provides a old school way of changing the volume. The following is a picture of the rotation sensor along with the interface kit. You can see the digital inputs, outputs and analog sensor ports, also notice that I have attached my sensor to port 7.

Now for the software to read the sensor values and to adjust the volume, I have created a C# program to do this. Primarily, I am leveraging a piece of code from Microsoft forums that has the implementation of IAudioEndpointVolume which is the interface for volume related functions on Vista. All that is left is to instantiate the interface kit and listen for sensor changes. The following code snippet illustrates the same.

   1: private void Form1_Load(object sender, EventArgs e)

   2: {

   3:     ifKit = new InterfaceKit();

   4:     ifKit.Attach += new AttachEventHandler(ifKit_Attach);

   5:     ifKit.SensorChange += new SensorChangeEventHandler(ifKit_SensorChange);

   6:     ifKit.open();

   7: }

In the sensor change method, I convert the value and pass it on the volume control class and change the vista master volume.

   1: void ifKit_SensorChange(object sender, SensorChangeEventArgs e)

   2: {

   3:     //checking which sensor triggered the change

   4:     //in this case the rotation sensor is attached to the 8th input

   5:     if (e.Index == 7)

   6:     {

   7:         //converting the sensor value to float

   8:         //sensor value could be anywhere from 0-1000

   9:         //in case of rotation sensor right side twist decreases the value

  10:         //thus we are substracting it from 1000 to get a higher

  11:         //value when rotating right side

  12:         float fVolume = (float)(1000-e.Value) / 1000;

13:

  14:         //float value is passed to the SetVolumeScalar method which sets

  15:         //the master volume

  16:         objMasterVol.SetVolumeScalar(fVolume);

17:

  18:         //updating the UI

  19:         SetTrackbarVolume();

  20:     }

21:

  22: }

23:

  24: /// <summary>

  25: /// Method update the UI

  26: /// </summary>

  27: private void SetTrackbarVolume()

  28: {

  29:     //getting the current master volume

  30:     //returned in a range of 0 to 1

  31:     float vol = objMasterVol.MasterVolume;

  32:     //multiplying by 100

  33:     int iVol = (int)(vol * 100);

  34:     //setting the trackbar value

  35:     trackVolume.Value = iVol;

  36:     lblLevel.Text = trackVolume.Value.ToString();

  37: }

Very simple to achieve, there are other types of sensors such as Light Sensor, Vibration sensor etc, which could result in more cool ways to change the volume. Full code is attached below, please use the code at your own risk.

Thanks
Anil Revuru

Links:
Phidgets Site - www.phidgets.com
Phidgets 8/8/8 interface kit with LCD - http://www.phidgets.com/products.php?product_id=1203
Phidgets Rotation Sensor - http://www.phidgets.com/products.php?product_id=1109
Vista Volume Control C# code - http://forums.microsoft.com/msdn/ShowPost.aspx?PostID=1287868&SiteID=1

Code Junkie : Cool Geeky Hardware

Bluetooth Device Development using C#

Volume Control using Phidgets Sensors