Biomedical Engineering Reference
In-Depth Information
Patient Interface. The device includes low-level user interface elements and some
patient feedbacks, motivating him and aiding a correct execution of the exercises. Two
leds indicate which hand must be used to execute the exercise and another led gives a
time reference blinking at 1Hz, which is useful for sustained position tests. They are
placed on the front panel for improved visibility. Moreover, a buzzer chimes whenever
the device detects a successful event, letting the user know that the device has effectively
captured his action. The device has been also provided with a double digit 7 segments
display, which has different functions depending on the exercise, providing:
- the percentage of the effort with respect to the maximum bound (extension and
torque),
- the number of correct sequences performed (finger tapping),
- the percentage of rotation over 10 turns (dynamic rotation).
Two buttons, placed on the horizontal plane and connected to two different external
interrupt pins of the MCU, provide a way for the patient to interact with the device. The
first one starts the exercise when the patient is ready, allowing to correctly position the
hand, whereas the second one can be used to skip a single repetition of an exercise.
3.2
Embedded Control Software
The operation of the MCU is controlled by the firmware loaded onto its flash mem-
ory, written in C and developed under the CCS v4.0 IDE by Texas Instruments. The
firmware flow is depicted in Fig. 3: as soon as all the initializations have been carried
out, the MCU enters the low power mode (LPM), where both CPU and MCLK are
disabled. The rest of the processing is then managed asynchronously by interrupt ser-
vice routines (ISR). All the resources present on the board, as operational amplifiers,
finger tapping MCU and Bluetooth module, are initially held in reset. Then the Blue-
tooth module is set up and configured by setting the operating mode, device name and
password. The firmware enters an endless loop, where each iteration corresponds to the
execution of an entire exercise. Inside the loop the MCU goes immediately in LPM,
waiting for the execution code of the exercise to launch coming from the PC. Receiving
the exercise code triggers the USCI A port ISR, which wakes up the MCU. Depending
on the selected exercise, some initializations are carried out, the ADC input channel is
set to the corresponding input pin (except for the finger tapping exercise) and the device
patient interface is set accordingly. After that the MCU goes in LPM again, waiting the
start signal (by pushing the white button), which unlocks the execution.
Fig. 4. Peak detection for the extension and isometric rotation exercises
 
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