Read data from Wii-balanceboard

Question

Im trying to get the output from a Wii Fit (balance board). I can find the device via the C++ Bluetooth enumerators but attempts to connect via a windows socket are failing.

Im wondering if anyone has had success in such a direction (C++, windows) I'd love to hear how you did it.

Answer 1

The Wii Balance Board is a HID device. To understand communications with the Balance Board, you need to know a little bit about Bluetooth HID. There's good information on WiiBrew about the Wiimote and the Wii Balance Board.

I don't think you can use Windows Sockets to connect to a HID device. The Windows Socket Bluetooth interface only allows you to connect to RFCOMM-based services. HID is based on L2CAP which is further down the Bluetooth protocol stack. There's some information at MSDN about that limitation.

If you're just looking to hack around with it, you can try Bluecove for Java. You may be able to do something using another stack (for example, Widcomm). If you're locked in to Windows and C++, you may have to look into writing an custom HID driver for the Balance Board.

Answer 2

As pwc said there is a limitation in the MS Bluetooth API, so with sockets you cannot have something else except RFCOMM, but this doesn't mean you cannot go down at L2CAP layer. What you have to do is to implement a client profile driver and you can use as starting point an article from MSDN: Creating a L2CAP Client Connection to a Remote Device and vice-versa: Accepting L2CAP Connections in a Bluetooth Profile Driver

Next of course as pwc said you have to study Bluetooth HID and WiiBrew for the communication protocol.

Also a good document to read is Bluetooth Wireless Technology FAQ - 2010 which states clear that it is possible to have L2CAP connections with Microsoft Bluetooth stack driver. Of course not with sockets.

Answer 3

When using HID on a Bluetooth device there is generally no need to create a L2CAP connection directly. All(???) of the Bluetooth stacks on Win32 have support for Bluetooth HID and provide access to the HID stream/control through the native Windows HID API. No (direct) L2CAP required! :-)

On WinCE there is built-in support for Bluetooth HID also, but I'm not sure there's a way to access a HID API.

That's how Brian Peek's wiimore library works -- it uses the HID API. The good thing about that is that one gets supports for all(?) the Bluetooth stacks that way -- they each support HID devices via the Windows HID API, whereas to use L2CAP directly one would have to support each of the stacks' APIs... (That's if they have one! BlueSoleil has no L2CAP API as far as I can see).

So, on Win32 one should just pair with the device and check that the HID checkbox is checked on its Bluetooth Service control panel tab (whichever Bluetooth stack is in use). In my 32feet.NET library one can discover the device and then ensure that HID is enabled for it with:

BluetoothDeviceInfo[] list = btCli.DiscoveryDevices();
var deviceInfo = list[n]; // Select the correct device
deviceInfo.SetServiceState(BluetoothService.HumanInterfaceDevice, true);

(That should work on MSFT and BlueSoleil; there's no API for that on Widcomm AFAIK -- although when paired it might be automatically enabled anyway).

The one possible exception case is that apparently some devices are not fully compliant with the Bluetooth/HID specs, I'm told the PS3 blu-ray controller is like that. Then one might want to try L2CAP connections directly -- however its likely that the stack's support for HID will interfere with third-party applications trying to provide the same service...