Note: TP-Link also markets a very different router under the same name.
Even though it is marketed as a "3G travel router", the TL-WR720N does not include a 3G modem. It simply means that the OEM firmware and GUI support a certain range of USB 3G modems. OpenWRT supports USB 3G modems, too. The router is powered through either a AC source (100-240V, Chinese-style foldable plug, i.e. two prongs without hole), or a micro-USB socket stub (5V).
The domestic Chinese/Asian versions and those for the European and American markets differ significantly. Only the rectangular version available from China has been tested, so far.
| Model Version || Launch Date || OpenWrt Version Supported || Model Specific Notes
| v3.0 || N/A || 14.07 || Chinese version (rectangular)
| v4.0 || N/A || 15.05 || Chinese version (rectangular)
| CPU || Ram || Flash || Network || USB || Serial || JTag
| Atheros AR9331@400MHz || 32MiB || 4MiB || 2 x 100MBit || 1 x 2.0 || Yes || Unlikely
SoC: Atheros AR9331
802.11 b/g/n 150Mbps
Powered via micro-USB (5V) or 100-240V
Tiny form factor (Chinese version)
9.2cm x 7.5cm x 2.8cm case
As from 28 April 2013, support for the TL-WR720N is present in the Trunk version of OpenWrt, see this thread on the forum for further reference.
The hardware of v4.0 is almost the same as v3.0 and the firmware id for it is 0x07200104 (0x07200103 for v3.0).
It appears the hardware switch must be set to "3G" to make the USB port work. Otherwise the port has power output but devices connected can't be detected by OpenWrt.
Note that the mount_root command will not work. (You can use the netcat method to install a fresh copy of the system if necessary.)
TP_IN is RX, TP_OUT is TX, and you may solder a ground above R323. The connection speed is 115200, N, 8, 1.
To access the u-boot bootloader, enter 'tpl'+<enter> when the 'Autoboot in 1 sec' message is displayed.
U-Boot 1.1.4 modification for routers
Forum member pepe2k made a modification of U-Boot 1.1.4 for Qualcomm Atheros SoCs based devices (the project is still being developed, so new devices and SoCs will be supported in the future). Up to date information, binary images and sources can be found on official GitHub repository.
This modification started from wr703n-uboot-with-web-failsafe project, but supports more devices, all modern web browsers, has a lot of improvements and other modifications (like U-Boot NetConsole, custom commands, overclocking possibilities etc.).