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SLN-VIZNAS-IOT User Guide, Rev. 1.1, 10/2020
NXP Semiconductors
default, will timeout and power down after 25 seconds have passed with an unrecognized
face in frame.
Triggering a registration or deregistration will reset the
“No_Face_Timer” and pause it
during the registration/deregistration so that neither of those processes will not be
interrupted by the system trying to go to sleep.
Once the system reaches the “Recognition Failed” state and is 5s from entering low power
mode
, a “Recognition Timeout” message like the following will be prominently displayed
at the top of the screen as a warning that the system is about to power down.
Figure 96: "Recognition Timeout" Message
To prevent the erasure of registered faces when the board powers down, when low power
mode is enabled, registered faces are automatically saved into flash, unlike how faces
must be explicitly saved into flash upon reset when low power mode is disabled..
NOTE: Faces are not automatically saved to flash when low power mode is disabled.
Once asleep, the board can only be awoken by the triggers mentioned in
the PIR sensor*, SW3, and USB Power (Power Cycling the kit).
Triggering a wakeup will cause the board to return to normal operation.
**NOTE: The PIR sensor as a wakeup trigger is currently disabled on the SLN-VIZNAS-IOT
due to a
manufacturing issue with the PIR sensor which causes unpredictable behavior when using the PIR
sensor as a wakeup source. This should not affect designs which use the PIR layout provided in
the SLN-VIZNAS-IOT HW schematic diagrams.
3.7 Audio Feedback
The SLN-VIZNAS-IOT comes with audio feedback prompts which are used alongside the
on-screen messages to provide information to the user. Currently, audio prompts for
“Registration Successful”, “Registration Failed”, and “Welcome” (Face Recognized) are
supported. To hear the audio prompts, a speaker must be soldered to the J3 connector
