Getting Started with the NXP EdgeReady MCU-Based Solution for 3D Face Recognition

Welcome to the SLN-VIZN3D-IOT Getting Started Guide! This guide will walk you through the process of getting up and running with your SLN-VIZN3D-IOT. This guide will discuss everything from unboxing your kit, to downloading, modifying and debugging the firmware source code for your kit.

Before we begin, make sure to check the box your kit came in for any marks or other damages, and should you find anything, be sure to report it to your local NXP representative.

1.1 Unbox

The box your kit arrives in should contain a few different things including:

• A Quick Start Card
• USB-A -> USB-C cable (x1)
• Four standoff screws
• IR camera module for future updates
• Fully assembled SLN-VIZN3D-IOT kit

It’s worth noting that the box also contains an additional IR camera sensor. This IR camera sensor is for users interested in evaluating only the 2D liveness detection and anti-spoofing capabilities of the kit, so attaching this additional sensor is not necessary for any of the steps in the following sections.

1.2 Power On

Before we begin, make sure to remove the protective film on both the 3D camera and the RGB camera (see below). This protective film is used to protect the lens of each camera during transport. Failing to remove these may cause the the depth and image capture to not work correctly.

Protective Film

To get started, take the provided USB-C cable and plug the USB-A end into your laptop/PC and the USB-C end into your kit’s USB-C port.

Plug in USB Cable

The kit’s USB connector supplies power to the board and supports data transfer capabilities for Mass Storage Device (MSD) programming and virtual serial port communication.

Once the application is ready, your computer will detect a new USB COM device and automatically install the required drivers. A message will confirm when the installation is completed.

After powering on, the onboard TFT screen will stream video directly from the RGB camera alongside a GUI overlay providing information such as:

• Locked/Unlocked Status (whether a face is currently recognized)
• Current App Type (Smart Lock/Access)
• ON/OFF status of Wi-Fi and BLE
• Number of registered users

GUI Overlay

At this point, the kit is fully operational.

1.3 Local Registration

One of the staple features of the SLN-VIZN3D-IOT is the ability to “register” and recognize faces without any cloud connectivity required whatsoever. By registering a face, the SLN-VIZN3D-IOT can then recognize that face again in the future.

Out of the box, registration can be done locally onboard the kit itself, or remotely using an Android^™ smart device.

This section will discuss local registration while the following section will focus on remote registration.

Local Registration

For the purposes of this tutorial, we will focus on registration using the onboard buttons, but for more information regarding registration via shell commands, be sure to check out the SLN-VIZN3D-IOT User Guide.

To begin registering a face, simply press and release the SW3 push button on the back of the kit.

SW3 Push Button

After releasing the button, the onscreen GUI will change in appearance similar to that shown below, and a corresponding “Starting Registration” audio prompt will be played.

Registration in Progress

As you can see from the picture above, while registration is taking place, the GUI displays:

• A “Registration” message
• Face alignment guidelines
• A countdown timer bar

The guidelines are used to assist with properly aligning your face during registration, while the countdown timer bar shows how much longer until the registration process will timeout and fail.

Retry Registration

As an additional measure to help with registering your face, the kit will even issue a warning audio prompt if too much of the side of your face is visible during the registration process, saying “Look at Camera” until your face is properly pointed towards the camera.

Should your face fail to register, simply press the SW3 button again to retry.

Once your face is successfully registered, the kit will display a "Registration Successful" message and a unique identifier will be assigned to your face. The number of registered users is automatically updated as well.

Registration Successful

After registration has completed, the onscreen GUI will revert back to its original state.

Normal GUI

As long as your face remains in the kit’s local database, your face will automatically be recognized by the kit any time it is in view of the camera. An onscreen "Recognition Successful" message and corresponding audio prompt will be played whenever a face is recognized.

Recognition Successful

Any subsequent attempts to reregister your face while it’s already in the system will produce a "User Already Exists" message and the registration process will fail, in order to prevent duplicate face registrations.

User Already Exists

1.4 Remote Registration

While it’s often convenient to register faces locally, there are many use-cases that require the ability to register remotely. For example, imagine a scenario where a hotel registers guests’ faces at a lobby kiosk before sending that face data to the guest’s room so that they can unlock their hotel room door using their face. In use-cases like these, the ability to register remotely is not only convenient; it’s required.

Remote registration on the SLN-VIZN3D-IOT functions similarly to the local registration flow we performed in the previous section, but instead of registering the face on the kit itself, the registration will be done remotely on an Android smartphone or tablet and then transferred to the kit’s local face database wirelessly.

Remote Registration

Before we begin, it is important to note that remote registration requires the use of an Android device running Android 8 or higher. If you don’t have an Android device available, feel free to skip this step and jump to the next video.

Before we can perform remote registration, we must first download and install the Smart Lock Manager App on our Android smart device.

To download the Smart Lock Manager app, go to the product page for the SLN-VIZN3D-IOT on the NXP website and navigate to Tools and Software at the bottom of the page:

Download Smart Lock Manager

Install the app by going to the Files App, clicking on Downloads, and selecting the smart_lock_manager.apk file. Tapping on the APK file will ask you to confirm that you want to install the application.

Installing The App

If this is your first time installing an APK file from the web, you may need to “allow app installations from unknown sources.” The process to enable this setting varies from device to device, so check the relevant documentation associated with your device for help.

Allow Unknown Sources

You may also be required to give additional confirmation if your phone does not recognize the app developer. Once installation has completed, open the application.

The first time the application is opened, you will be prompted to give various permissions required for the app to run correctly. Make sure to approve all of them.

Smart Lock Manager Verify Permissions

Additionally, verify that Bluetooth is activated on your Android device.

Bluetooth Enabled

The app’s home screen will display a list of kits within Bluetooth range of your Android device, using a unique identifier for each kit. Select the kit that you want to connect to.

Smart Lock Manager Home Screen

An authentication screen will ask for a password to connect to the board. By default, this password is 000000.

Authentication Screen

Once authenticated, the subsequent screen will list the users already registered to the connected kit. From this menu, we can manage the users stored in the kit’s local face database.

User List

Click on the "user_000" listing corresponding to the face we registered locally in the previous step and press the "Delete User" option.

Delete User

Confirm deletion by clicking "Delete" on the prompt that appears. The "user_000" face will automatically be removed from both the list on your Android device and the local database on your SLN-VIZN3D-IOT.

Confirm Deletion

Now, click the "Add User" button in the lower right-hand corner of the screen.

Align your face with the camera and click the snapshot button at the bottom of the screen once the box around your face turns green.

Add Remote Face

Assign a username to your face by typing in the text box labeled "Name". Once you are satisfied with the name and picture, click "Register" in the upper right-hand corner of the screen. At this point, the face you just registered will automatically be synced with the connected SLN-VIZN3D-IOT kit.

Add Remote Name

To confirm successful registration, position your face in front of your SLN-VIZN3D-IOT kit and verify that your face is successfully recognized.

Note The first time a face remotely registered is recognized, the recognition may take a little longer to compensate for the quality difference between the kit’s camera and the Android device’s camera, used for the (remote) registration.

1.5 Liveness Detection

The Smart Lock application flashed by default on the SLN-VIZN3D-IOT is able to perform “liveness detection” on faces detected by the kit. “Liveness detection” refers to the ability to discern between a real face and a “fake” face (ex. a picture or 3D model of a face). Liveness detection is used to protect against “spoof” attacks in which a malicious user may try to coopt someone’s likeness.

Real vs Fake Face

The three main types of spoof attacks that the i.MX RT1170 Smart Lock solution can detect are attacks using pictures on a phone display, printed black and white or color photos, and attacks using 3D models like silicon and rubber masks.

Types of Attacks

We can test the liveness detection feature by simply presenting a fake face to the camera. A UI message and an audio prompt will confirm when a fake face is detected.

Fake Face Message

Certain spoof attacks, primarily those using phone displays, may not trigger any feedback whatsoever. This is because no face can be detected by the IR camera.

IR Camera During Phone Display Attack

Of course, spoof attacks in which no face can be detected will not trigger a recognition either, so there is no concern that a spoofing attempt in this scenario might succeed.

1.6 Low-Power Mode

Many battery-based applications require the ability to conserve power during periods of low usage in order to maximize potential battery life. The SLNVIZN3D- IOT was designed with many of these use-cases in mind, and as a result, the Smart Lock application flashed by default possesses the ability to enter a low-power mode state that significantly reduces the amount of power consumed by the kit.

Enabling low-power mode causes the SLN-VIZN3D-IOT to enter an energy saving state where the RT1170 MCU is set to a deep-sleep mode and the power to most of the kit’s peripherals is shut off. While low-power mode is active, only a select few peripherals remain active, including a push button, the PIR sensor and the QN9090 Bluetooth module, for use as wakeup triggers to reset the system back to normal operation.

Low-Power Mode Summary

Sleep mode on the SLN-VIZN3D-IOT can be initiated manually, using a push button, or automatically, using a combination of timers and other event triggers. The following instructions will be focused on the manual option. For more information about the automatic low-power mode configuration and alternative wake up sources, see the Low-Power Mode section of the SLN-VIZN3D-IOT User Guide.

Manual vs. Automatic

To set the system into a low-power state, press and hold the SW1 push button located on the back of the kit for at least 2s before releasing it.

SW1

A splash screen and a corresponding audio prompt will indicate that the kit is entering sleep mode.

Low-Power Mode Splash Screen

Pushing the SW0 button will wake up the RT1170 microcontroller and restore the system to normal operation.

SW0

1.7 Connecting to Serial CLI

The Smart Lock software installed by default on the SLN-VIZN3D-IOT kit provides a convenient serial-based CLI useful for configuring various application settings and retrieving useful runtime information. Connecting to the kit’s serial-based CLI can be done using a serial terminal emulator program like PuTTY or Tera Term.

Before we begin, make sure that you have a serial terminal emulator like PuTTY or Tera Term installed on your computer.

PuTTY and Tera Term

Note If you are using a Windows machine, we recommend Tera Term for its ability to automatically discover connected COM devices and reconnect to a device in the event of a disconnect.

Establish a serial connection with your device by entering the serial settings [115200, 8, 1, None, None] shown below, making sure to replace the COM port setting with the COM port associated with your kit.

Serial Settings

Once connected, a blank terminal screen will appear that will echo back any characters that you type. Typing the "help" command will print a list of all available commands and a brief description of their functionalities.

"help" Menu