Background

The car repairer uses a mini USB camera as an endoscope to repair the car. The endoscope used by the doctor to view the internal organs of the patient. The key is off the Toilet, looking for a waterproof USB camera with a hook (joking), and so on.

Some time ago, I specially studied android devices to connect multiple USB cameras because I was obsessed with doing another thing, at my spare time from searching relative materials, supporting conditions to purchase hardware (camera, smart machine), and finally implementing external connection USB cameras based on an open-source code on GitHub.

The purpose of this article

This article implemented using Xiaomi tablet to connect multiple usb cameras. Xiaomi tablet is a android device like ipad. A application show all usb camera's record at the same time.

1. Recording, convenient search in the future.
2. Sharing, convenient more people search.

The requirements

android smartphones

support OTGOTG

support UVC protocol

usb camera

support UVC protocol (most USB camera support UVC)

usb 3+ hub

support OTG

type c convet to usb

support OTG

Devices that I brought

• A Xiaomi pad (¥999.00)
• A UGREEN CR109（USB3.0 hub with power, ¥65.00）
• 4 Aoni G10 USB camera (¥264.00)
• A UGREEN 30176（Type-c convert to usb port, ¥25.9）

Total money: ¥1353.9

The result

Notice

1. It's bettter USB hub with power, maybe android device has insufficient power.

Image cannot be displayed

You need release resource that you applied when you deubug.

activity_main.xml

<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal">
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="50dp"
        android:id="@+id/release"
        android:text="release all cameras"/>
</LinearLayout>

MainActivity.java

protected void onCreate(final Bundle savedInstanceState) {
     // ......
     releaseBtn = (Button)findViewById(R.id.release);
     releaseBtn.setOnClickListener(mReleaseOnClickListener);
     // ......
}
private final OnClickListener mReleaseOnClickListener = new OnClickListener() {
   @Override
   public void onClick(final View view) {
      if (DEBUG) {Log.v(TAG, "camera numbers-->" + mCameras.size());}
      for (final CameraRec rec: mCameras.values()) {
         if (DEBUG) {Log.v(TAG,  "release camera-->" + rec.mCamera.toString()+);}
         rec.release();
      }
   }
};

adb shell
cd sys/bus/usb/drivers
ls

If you are interested in this article, please email me. frankshaohua@gmail.com