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MCF5249 Fingerprint Security Reference Design User’s Guide
MOTOROLA
At startup, the application runs a calibration routine that adjusts the finger detection sequence to ambient
sensor readings. During this routine, the LCD displays the following message, asking the user to refrain
from touching the sensor until the calibration is complete:
Sensor calibration:
Please dont touch
The application has two modes, enrollment and verification, selected via the switch on the daughtercard. If
the switch is set to verification when the application is run, verification begins and the application asks for
a finger to be placed on the sensor. However, since this is the start of the demonstration, there is no template
to which the fingerprint can be compared; therefore, verification will fail. Set the switch to enrollment, and
place a finger on the sensor to reset the software to enrollment mode.
3.1
Enrollment Mode
In enrollment mode, the application runs the fingerprint acquisition and algorithm between four and seven
times in order to create a template for future verification. The LCD displays the following message for each
of the runs:
Enroll: Score(0) = --
please re-place finger
If a finger is not placed on the sensor, a timeout occurs, the enrollment fails, and the LCD displays the
timeout message below. The application then returns to the start of the enrollment sequence.
Enroll: Score(1) = --
Enrollment failed!..
(timeout reached)
Upon completion of four or more successful fingerprint acquisitions, the enroll score shows an actual value,
as in the example below. This value changes based on the clarity of the image, the number of minutia
available for extraction, and the weight each minutia has been given according to prior matches. Though it
is possible to keep the finger on the sensor throughout the seven acquisitions, to increase template quality,
the finger should be lifted and replaced between each acquisition.
Enroll: Score(4) = 41%
enrollment SUCCESFULL!..
switch to verification
Completing seven acquisitions is more likely to produce a higher score because, with each additional
acquisition, specific minutia can gain a higher weighting.
Enroll: Score(7) = 77%
enrollment SUCCESFULL!..
switch to verification
To stop the enrollment process, do not touch the sensor until a timeout has occurred. The LCD will display
the final enroll score and will ask for the switch to be moved to verification. If the final score is less than
25%, then enrollment is insufficient and the process will be restarted as in the example below.
Enroll: Score(5) = 22%
enrollment failed!..
(Score < 25%)
NOTE
The demonstration will only store one fingerprint template at a time.
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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