Flash for the first time

1. WARNING: Double check your router's spec: Tenda AC9 (Broadcom, 16M flash, 64M RAM, no USB). A mismatched router will be bricked.
2. Download the firmware file (*.trx).
3. Connect your computer to one of the router's LAN ports and run ping 192.168.0.1 (or ping -t 192.168.0.1 on Windows).
4. Unplug the router, and plug it back in while holding down the reset button. Wait about 30 seconds until ping success, then release the reset button.
5. Open your browser and navigate to http://192.168.0.1. Clear NVRAM first, then upload the firmware.
6. Wait patiently for the router to reboot. Done!

Upgrade

1. Download the firmware file (*.trx).
2. Open the router's web management interface, navigate to Administration - Firmware Upgrade.
3. Upload and done.