This article demonstrates how to assign the volume up button on your Android device to trigger a scan (or read) from the paired barcode scanner or RFID reader.
1. Open the sidebar menu by tapping on the hamburger icon (located at the top left of the screen) or by swiping from the left edge of the screen to the center of the screen.
2. Tap on Settings.
3. Tap on Trigger settings.
4. Tap on Trigger Scan to assign a button to trigger the last paired scanner to scan (for barcode scanners, it will trigger the laser; for RFID readers, it will trigger a read).
Alternatively, select Trigger Camera to assign a button to trigger the Android device's camera.
5. Select either Volume UP (for the volume up button) or Volume Down (for the volume down button).
You can see here that I've assigned the volume up button to trigger a scan.