Biomedical Engineering Reference
In-Depth Information
Fig. 5. Detection of the edges onset and end of the typical dynamic rotation signal for
segmentation
The finger tapping exercise differs from the others because there are no analogue
signals involved. The MCU on the main board acts as the master of the I2C channel,
requesting the 8-bit word (one bit for each key in the touchpad) provided by the sen-
sorized aid whenever the sampling timer expires. For this exercise, the timer has been
set differently for a sampling frequency of 50Hz, which is in line with the state of the
art [6] and allows the complete scanning of the 8 keys in a sampling period, in the
worst case (when all the keys are touched). As a new word is received, it is mirrored,
if necessary, in order to have the least significant bit always referred to the thumb key.
When the first not null data is received, the algorithm detects the less significant bit
set to 1 and creates a mask used, at the next touch, to check if the next key tapped
corresponds to a less significant bit or not. If this is true, the mask is updated and the
processing goes on, otherwise an error flag is set. The sequence terminates when the
thumb touch is detected (lsb = 1). If the number of touches is equal to five the valid
sequence counter is incremented or, if either the error flag is set or the sequence length
differs from five, the bad sequence counter is. This processing is performed in real-time
and when the exercise is complete, an additional routine computes the relevant statis-
tics, including average touch duration for each finger, average distance between them,
total consecutive touches and total duration of the exercise.
4
The Advanced Stand Alone Physician Interface
By means of a standalone GUI based on the Qt 4.7 framework (a C++ graphic frame-
work), the physician can monitor in real-time on a host PC the execution quality of the
exercises, also extracting the information needed for the hand functionality assessment.
Since the Bluetooth device driver exports a serial interface towards the user applica-
tions, it can be managed using the QtExtSerialPort class which is not included in the
framework by default but can be integrated with minor effort. Once the link has been
established the device sends its calibration values to the host, which will be used to
perform the scaling of the received data on the PC, in order to lighten the processing on
the device microcontroller. The communication is handled by means of a simple proto-
col made of 8 bit wide control codes. In the main window it is possible to choose the
exercise and the hand to use whereas the exercise progress can be analyzed in a differ-
ent window, specific for the selected exercise, which pops up as soon as the exercise is
started. Both windows are depicted in Fig. 6. In every exercise-specific window there is
the possibility both to stop the execution and to go back to the main window, where the
physician can select a new exercise.
 
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