This article outlines the procedure to force an Elo Backpack into Stretched/Fullscreen mode

Note: This process is only needed in cases where you want to connect an Elo Backpack to a square monitor with standard aspect ratio (not wide aspect ratio monitors). This does not change the output resolution, but stretches the image to use all the pixels of the screen. 

Requirements:
•  Host PC (Linux, Mac, Windows) with ADB and Fastboot installed
•  USB A-to-A cable
•  Elo Backpack and connected Elo monitor
•  Elo Fullscreen Script File (elo_cust.xml)
 
Process:
1. Verify that your Elo Backpack device is up-to-date with the latest EloView Image.
2. Open and configure Developer Options on the Backpack to ensure that the host PC can do ADB debugging. (Reference TB000033 for details)
3. Unplug power to the Backpack, then press and hold the HOME button and reconnect power cable.

4. Plug in the Type A USB to the port next to the DC power connector. Plug the other end to the host computer.
5. Ensure your system sees the fastboot device. From Command Prompt/Terminal, type “fastboot devices” à the serial number should show up
6. Type the following commands:

7. Remove the USB Type A cable from the Backpack
8. Power cycle the Backpack by removing power cable and reconnecting
9. After the device has booted, connect to the unit through ADB (Reference TB000033 for details)
10. Copy Elo-provided XML script into same folder as ADB/Fastboot executables on the host PC.
11. Type the following commands:

12. Upon reboot, device will display in stretched (full screen) mode – process is complete

See related article:
BackPack 4.0 Supported Video Resolution and Display Size Adjustments