“Knock-Knock” Message Board
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Our project implements a “Digital Message Board”: its primary function is to receive text messages and display the text on a monitor. For example, when mounted on the door to an office, the message board may be used to announce that the occupant of that office will be late in arriving due to traffic congestion on the way to work. This is the default mode; the time of day is also displayed. The message board has a built-in camera that enables two additional functions: capturing an image of someone knocking on the door and sending it by multimedia mobile service to a specified phone number, and with facial recognition software identifying specific individuals when they come to the door and showing them user-specific announcements. For example, the person whose office it is can send the system daily schedule reminders that appear when his/her face is recognized. We use a Raspberry Pi 4 computer as the main control unit to realize message transmission, facial recognition, and graphical user interface display. The message board receives text messages through WiFi from a cloud-based service provided by Twilio. When the message board receives a message from a mobile phone containing the desired recipient or the group, it decodes the message, compares it with an SQL user database established in advance, and stores it in the corresponding location. If the facial recognition system matches the camera image face with one the database, any messages corresponding to that user will be displayed.