Asus T-Mobile Cellspot

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[edit] Hardware Specifications

ASUS TM-AC1900 (T-Mobile)
CPU1 Broadcom BCM47081A0 @ 800 MHz
FLA1 128 MiB
RAM1 256 MiB
ETH chip1 Broadcom BCM47081A0
Switch Broadcom BCM47081A0
Ethernet Ports 1-1GbE-WAN
USB Ports (2) 1xUSB 2.0
1xUSB 3.0
WI Chip1 Broadcom BCM4360
MIMO status 3x3:3
802.11 protocols b/g/n
WiFi Operating Frequency 2.4 GHz
WI2 Chip1 Broadcom BCM4360
MIMO status 3x3:3
802.11 protocols a/n/ac
WiFi Operating Frequency 5 GHz

[edit] Introduction

The Asus M-AC1900 (T-Mobile) is a hobbled RT-AC68U that can be upgraded to a fully functional RT-AC68U.
NOTE: This wiki is in the process of major editing due to broken links and outdated information.
SEE Flashing TM-AC1900 to RT-AC68U/P for more information.

[edit] Installation

[edit] CFE Downgrade is necessary to enable flashing firmware

This upgrade is a little trickier than most because the procedure involves not only navigating DD-WRT firmware, but navigating the CFE The newsgroups document that CFEs are able to control / deny firmware upgrades, which is the reason for 'downgrading' to firmware that does not prevent firmware changes.

******Updated guide to CFE Mod ****** here but doesn't mention flashing firmware

Version 2827 is firmware locked to only TMobile branded firmwares. Not only is the firmware locked (disabled Telnet), it installs CFE, which locks the router from any non TMobile branded firmware via recovery mode and GUI mode. The only way to change firmwares is to downgrade to an older TMobile firmware (1703 for example), enable Telnet, and then replace the CFE (preferrably with an Asus RT-AC68U version - such as

Many details in this guide including links to the older 1703 firmware and all CFE's and utilities needed

if you're on CFE, which is not locked, and try to use the latest Asus branded firmwares, it will update your CFE and, lockout out all non TMobile firmware's again. Once you get to DD-WRT, doesn't matter anymore unless you decide to go (back) to Asus stock RT-AC68U firmware, latest copies.

For more information see UKEE's post here.

[edit] Links: verified firmware

There are numerous choices each with its strengths. DD-WRT / Kong are filled with features. Merlin to stay as close to the original firmware to ensure maximum performance.

  • DD-WRT builds: FIRST flash a .trx build from the asus ac68u folder, to upgrade use the .bin file. Beta downloads
Merlin Changelog documents newest updates and firmware candidates

[edit] Links to tools and other files

Asus tools to revert FW ("Engineer" or UKEE to verify this). (broken link)

[edit] Links: verified CFEs

Verified: from the tmo2ac68u package. (broken link)

CFE_ASUS_RT-AC68U_1.0.2.0 (US).txt

CFE_ASUS_RT-AC68U_2.1.2.1 (US).txt (??? user to verify)

[edit] Procedure

Before starting the process, obtain the tmo2ac68u package Broken Link. Tools and Firmware used in this process must be obtained and unzipped. Copy the mtdwrite utility and the target CFE to a flash drive. Fortunately, there is a (lengthy) YouTube video that demonstrates the different processes below. gatorback: because it is lengthy I skimmed through it ONLY when I was stuck. After you have installed \ downgraded T-Mobile's software, you will want to change the firmware: there is a good article discussing the various versions of firmware here.

    High Level  Steps:
      * Gain Telnet Access: flash TMO 1703 firmware via CFE webserver
      * Copy original CFE to USB memory stick
      * Copy data from original CFE to target CFE
      * MTD-write target CFE to boot sector
      * mtd-erase2 nvram 
      * nvram get bl_version
      * Flash final target firmware via CFE Webserver

1) Enable Telnet: Place router in recovery mode and upload TMobile firmware xxx.1703 (found in tmo2ac68u package Broken Link) through the CFE web UI. Enable telnet by navigating: Administration -> System -> Enable Telnet=Yes -> click 'Apply'


Alternative method: An alternative to flashing 1703 to enable Telnet
 **CAUTION**:  If you enable telnet, then erasing the NVRAM may disable efforts that enable Telnet.

Always perform a NVRAM reset after flashing firmware, reboot and allow 5 minutes to rebuild NVRAM variables.

    ** Power off the router
    ** Hold the WPS Button
    ** Power on the router and keep the WPS pressed for 10-15 seconds
    ** Reboot as necessary 


    nvram get bl_version

This process involves telnetting and copying the existing CFE to retrieve data to USB stick, paste this data into the target downgrade CFE file, and writing the modified target CFE file back to the router.

3) Place router in recovery mode and install Merlin firmware via through the CFE Webserver recovery mode (easier).

4) Perform NVRAM reset

5) Flash DD-WRT and perform NVRAM reset

6) Go to your fridge and reward yourself with your favorite beverage and add your username here:


[edit] Tests to perform after installing DD-WRT firmware

  • NVRAM available immediately after install
  • Speed Test measurements in 2.4 and 5 Ghz bands
  • Verify USB 3.0 speed measurement
  • Please update any other meaningful or useful test metrics / measurements

[edit] Further Information, References, Additional Reading