How to: WRT1900 ACS v2 Install Firmware Through Serial Port

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lyrrad
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Joined: 28 Jan 2012
Posts: 17

PostPosted: Tue Jan 30, 2018 7:18    Post subject: How to: WRT1900 ACS v2 Install Firmware Through Serial Port Reply with quote
Optional: You may want to remove the antennas to prevent any breakage from the task you are about to do.


Section 1: Remove the Blue Portion of Cover to Reveal Serial Port

Flip the router and remove the screws from the feet of the blue portion

Keep in mind that the screws for the Black portion of the cover are different from the Blue portion. Please do not mix this up.



Use some force to pry the blue portion of the cover away from the black.




Section 2: Connect the Router to the Computer

You will need to connect both the Ethernet port and Serial Port to the computer. For this guide, I used a laptop running Windows 10.

For convenience you may also want to purchase a Serial to USB Adapter. This can be purchased rather cheaply. The one I used is found in this link: https://www.aliexpress.com/item/32775876897.html?spm=a2g0o.productlist.0.0.432f6476nqQAGA&algo_pvid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd&algo_expid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd-31&btsid=f443b5dd-71c3-42f6-8878-84506882736c&ws_ab_test=searchweb0_0,searchweb201602_9,searchweb201603_52



Once you have removed the Blue cover, you will see the Serial Port to the right (When router is facing up)


Connect the adapter as follows (color depended on the adapter that I bought, but in general, I believe this to be the common color key):
Pin 1: Ground - Black
Pin 2: TX - White
Pin 3: Empty
Pin 4: RX - Green
Pin 5: Empty
Pin 6: Empty




Your set up should look similar to this image:




Section 3: Set up computer to access router

You will need two software. A TFTP Server (http://tftpd32.jounin.net/tftpd32_download.html) AND a Serial Interface (You can use Putty https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html, however I used Tera Term https://osdn.net/projects/ttssh2/releases/)

You will also need the Firmware file. You can download the WRT1900ACS v2 stock firmware from this link: https://www.linksys.com/us/support-article?articleNum=165487

First Install the TFTP Server. Once it is installed, place the firmware file inside the TFTP server's current directory. The firmware file in the following image was renamed to "cobra". I remember doing that because the command I ran to update seemed to default to finding the name "cobra" as the firmware file. You can of course change that default name to something else so that you do not follow that step


The router's default entries are as follows:

Server IP Address: 192.168.1.254
Subnet Mask: 255.255.255.0
Gateway: Not important
DNS: Not important

You have two options, change the router's default entries OR change your computer's Ethernet port default entries. Generally most guides I saw as well as what I did was to change the address on the Ethernet port of the computer. The point here is to sync the addresses so that you can transfer the firmware from the TFTP server (on the computer through the ethernet port) to the router (through the router's ethernet port)

Once that is done open your tftp server and make sure the current directory is the one where the firmware is. And the Server interface is the one for your ethernet port. In the following picture, the ethernet port is not set up to 192.168.1.254 because I did the screenshot after reverting back to default ethernet settings. But when you do the procedures prior to this step, that address will be 192.168.1.254


Now also open your Serial Interface (For my case, Tera Term)

Choose Serial. The COM port will depend where you place the Serial to USB adapter.


Then click ok and now look for the serial settings


The settings there should be as follows. The only thing I change was the baud rate to 115200, If you don't make that change, all messages coming from the router will be gibberish on your computer screen:

Port: COM <whatever com port the adapter is attached to>
Baud Rate: 115200
Data: 8-bit
Parity: None
Stop: 1 bit
Flow Control: None




Section 4: Terminal Commands to Install the Firmware

Note for WRT1900 ACS V1 users:
Base on this link and forum member dertester123: https://community.linksys.com/t5/Wireless-Routers/wrt1900acs-brick-and-not-connect-serial/td-p/982681/page/4, there is a glitch with V1 in that you need to first turn on the router before connecting the RX/TX/Ground pins to the router's serial port. Once the router is turned on, in 3-5 seconds, insert the pins to the serial port and hit the key to prevent a boot.

If not V1 user, continue from here:

You can finally turn on your router!
When you do so, Tera Term will have a bunch of text displayed. When you reach the point where it says click any key to abort boot, you may click any key (There is a 3 second delay before the boot proceeds)

Run the following command to see if the router can communicate with the computer:

Code:
ping 192.168.1.254


If the reply is "alive", you can proceed to the next step. If not, turn off all firewall settings. For some reason, this can sometimes interfere with the connection. If you can't figure out why you cannot ping, maybe try another computer (which was what I did)

Option 1

If you set everything up following the procedures of this guide, the only command you need to run is:

Code:
run update_both_images


In the Tera Term interface, you will see an asterisk "*" while the firmware is being transfered from the computer to the router. However if you see "T", the transfer has timed out.

and voila! You are done. Turn the router on and off again and all should be running fine.

Option 2
Else you can follow these steps

Check the router's default entries

Code:

print ipaddr
print serverip
print netmask

print firmware_name
or
print firmwareName


If any of those are different than the one that was set up in this guide, change the entries (using code setenv for Set Environment). Most likely the only ones you will need to change is serverip and firmware_name (or firmwareName). for firmware name, change the code with "< >" sign to the firmware name that you have.

Code:

setenv firmware_name <name_of_your_firmwarefile.bin>
setenv serverip 192.168.1.254

The rest is optional
setenv ipaddr 192.168.1.1
setenv netmask 255.255.255.0


Then after that is done, ping server ip to make sure you can connect:

Code:
ping 192.168.1.254


If you get a return of "alive" you can proceed to the run command. There are two commands that can be used to flash the firmware.

One installs only on the primary partition
Code:
run flash_pri_image


The other installs on both partition, I prefer the both option.
Code:
run update_both_images


In the Tera Term interface, you will see an asterisk "*" while the firmware is being transfered from the computer to the router. However if you see "T", the transfer has timed out.

and voila! You are done. Turn the router on and off again and all should be running fine.


Last edited by lyrrad on Wed Sep 04, 2019 2:12; edited 4 times in total
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lyrrad
DD-WRT Novice


Joined: 28 Jan 2012
Posts: 17

PostPosted: Tue Sep 03, 2019 6:40    Post subject: Reply with quote
Is it possible to sticky this?
PIZZEDMEOFF
DD-WRT User


Joined: 12 Dec 2017
Posts: 244
Location: FL

PostPosted: Tue Sep 03, 2019 13:01    Post subject: Reply with quote
Great work on this.

fix the link to the cable to

https://www.aliexpress.com/item/32775876897.html?spm=a2g0o.productlist.0.0.432f6476nqQAGA&algo_pvid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd&algo_expid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd-31&btsid=f443b5dd-71c3-42f6-8878-84506882736c&ws_ab_test=searchweb0_0,searchweb201602_9,searchweb201603_52

TFT server link:
http://tftpd32.jounin.net/tftpd32_download.html

_________________
Downloads:
ftp site: ftp://ftp.dd-wrt.com/betas/2021
SVN Timeline:
https://svn.dd-wrt.com/timeline
Commands:
Misc: sleep 10;stopservice nas;stopservice wlconf;startservice wlconf;startservice nas
samba: { sleep 30; stopservice samba3; startservice samba3; } &

WRT1900ACv1:

WIFI: 2.4ghz: NG-mixed, 20mhz channel width, channel follows AP, WPA2-CCMP-128.
WIFI: 5ghz: AC/N mixed, 40mhz channel width, channel 100+upper, WPA2-CCMP-128.
Misc Info: WPA2 Personal: "CCMP-128 (AES)" Static IP's VIA Mac+Host, SFE Enabled, No Rebind, Strict, no-resolv. NOTE: this is now just a wireless access point so to speak but all settings still apply to what ever wireless person connects.
lyrrad
DD-WRT Novice


Joined: 28 Jan 2012
Posts: 17

PostPosted: Wed Sep 04, 2019 3:56    Post subject: Reply with quote
PIZZEDMEOFF wrote:
Great work on this.

fix the link to the cable to

https://www.aliexpress.com/item/32775876897.html?spm=a2g0o.productlist.0.0.432f6476nqQAGA&algo_pvid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd&algo_expid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd-31&btsid=f443b5dd-71c3-42f6-8878-84506882736c&ws_ab_test=searchweb0_0,searchweb201602_9,searchweb201603_52

TFT server link:
http://tftpd32.jounin.net/tftpd32_download.html


Thanks, updated with your suggestion.
lbddwrtnoob
DD-WRT Novice


Joined: 25 Nov 2019
Posts: 12

PostPosted: Wed Oct 13, 2021 1:56    Post subject: Reply with quote
lyrrad wrote:
PIZZEDMEOFF wrote:
Great work on this.

fix the link to the cable to

https://www.aliexpress.com/item/32775876897.html?spm=a2g0o.productlist.0.0.432f6476nqQAGA&algo_pvid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd&algo_expid=8259417d-25f7-4eef-9a5a-3e7a7567f0cd-31&btsid=f443b5dd-71c3-42f6-8878-84506882736c&ws_ab_test=searchweb0_0,searchweb201602_9,searchweb201603_52

TFT server link:
http://tftpd32.jounin.net/tftpd32_download.html


Thanks, updated with your suggestion.


Guys. I can't thank you enough for this guide. As a COMPLETE noob (username checks out) I ordered a USB to SERIAL TTL cable, downloaded PuTTY and Tftpd64 and followed these instructions to the letter. I successfully restored my router first attempt.

I have some 'noob targeted' additions to the instructions:

1. Connect your computer to the router via one of the four ETHERNET ports and NOT the INTERNET Port. Yes. I am that stupid. Don't be me. Be smart.

2. In WINDOWS at least, you have to determine the correct COM port that your USB/SERIAL is attached to. (Go to Device Manager and look under the USB section). It isn't always COM1. Mine was COM3.

3. Windows 10 Home - Changing your computers IP address is easy and is immediately overwritten when needed by hitting "DHCP/Automatic" rather than "manual". It's not a big deal once you know how. Don't forget to revert back to your original (likely Automatic) settings when done.

3B. *HOWEVER* In WINDOWS 10 (and I think 11) there is a bug ( as of Oct 2021) that does not allow you to edit your IP settings via the taskbar 'Network and Internet Settings' options. You HAVE to go through Control Panel\Network and Internet\Network Connections then select CHANGE ADAPTER SETTINGS, double click ETHERNET and then change the INTERNET PROTOCOL VERSION 4 (TCP/IPv4) setting. Going through the menu bar will lead to a CANNOT SAVE SETTINGS error.

4. You need to rename the file "cobra.img", not just "cobra" or you will cause a FILE NOT FOUND error.

5. DISABLING the firewall is probably a recommended course of action for noobs. Too much is going on to be dealing with firewalls as well. Just remember to re-enable it.

6. I used PuTTY rather than lyrrad's chosen app. In order to change ALL of the recommended settings for the SERIAL connection I had to access further configurations by accessing the LHS menu: Connection / Serial and fix the parity/flowbits settings there.

7. Don't mess up the 4 screws. The two at the rear of the modem are a different size to the two at the front. If you screw it up, the rear screws have the bigger thread.

8. For clarity --- on the cable you DONT need the red (power) cable connected to anything for this method. And so discussions as to whether this is a 3V or 5V or 500V in other posts are irrelevant to this discussion.

I hope in someway I have been able to give back to the community who have provided me with so much assistance themselves. Thank you.
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