Please refer below procedure to upgrade firmware(to use MstarUpgrade.bin file).
1. Copy MstarUpgrade.bin file to USB drive root.
2. Short connector X402 GND and POWER pin.(The connector is for other model keypad, so the POWER pin is for POWER button)
3. Switch on AC power.
4. EP5520T will start to upgrade after 10 seconds.
5. Remove the jumper from connector X402.
6. Reboot EP5520T after done the upgrade.