WII BALANCE BOARD COP DETECTION
BACKGROUND
Currently, there is no single test to determine whether a young child (especially one with mild symptoms) has cerebral palsy- diagnosis is based on multiple factors involving qualitative observations, motor analysis, and looking at other factors and symptoms.
A quantitative measure that can provide contributing information to a diagnosis is measuring EMG activity while collecting center of pressure (COP) data in order to verify that the muscles activity is close to max as that makes the test across typical and symptomatic patients the same.
The goal is to develop a device or data collection solution that will allow us to collect COP and EMG data simultaneously, not only in the lab but in the homes of pediatric patients as well.
FINAL DESIGN
There were three major components of the final solution:
1. Raspberry Pi 3:
The Raspberry Pi was used as an intermediate device that both communicates with the Wii Balance Board and the data collection PC. One of the main reasons I decided to use the Raspberry Pi was because I was able to find a Python library that would not work with the Bluetooth drivers of our Windows 10 machine. Although that was the primary motivation for me to use the RPi in the first place (I could use the Python library with no issues with the Bluetooth driver), a later requirement that the requesting PI told me was that they would like a way to have the device output a pulse that could be used as an input to a National Instruements DAQ such that EMG data could be properly aligned with COP data- this was an easy requirement to fulfill using a GPIO pin on the RPi. I 3D printed a box for the RPi and installed a button to turn on and off the RPi, since the only way to do it otherwise was unplugging it.
2. Wii Balance Board:
Again, I utilized the Wii package described in the above link. Using the Wii Balance Board was relatively straightforward. After the power button is pressed, we could connect the board to the RPi using the connect button- the RPi was looking for the hardware ID of the balance board, so it would automatically connect after that and the board was ready for use. Compared to other COP measuring devices, the Wii Balance Board was significantly cheaper (less than $100 vs over $4000).
3. Data collection PC
The PC was running Matlab and connected to the Raspberry Pi via a USB to TTL cable. I wrote a Matlab GUI that would send commands such as "connect", "collect", "zero", and "disconnect" to the Raspberry Pi, while also communicating with the NIDAQ and collecting EMG data whenever COP data was being collected. The GUI would also display COP data in realtime and have a replay and pause option after data is collected.
*NOTE: the deadline I was given for the device was "ASAP" and budget was minimal so I tried to come up with a solution that would be accurate, consistent, robust, done relatively quickly, and use materials we already have in the lab. Thus, although I know there are other methods that would have worked instead, this was the one that met my design requirements and deadline and budget goals.
FINAL THOUGHTS
So far, this solution has worked really well for the purpose of a portable COP measurement collection device! If I had more time to work on the project, I would have written a Matlab library to communicate with the Wii balance board directly so that the Raspberry Pi would not be necessary.