My router is TPLINK WR 740n V5
I am trying to install openwrt factory firmware v4.28 on it using web interface (Though it is V5 router. )
(experimenting that if it works on v5, Because most of the thing are similar in v4.28 and v5)
when I do it I get ,

Error code: 18005
Upgrade unsuccessfully because the version of the upgraded file was incorrect. Please check the file name.

I tried changing firmware name to TPLINK firmware names , but it is not helping, in previous 740n version 4.28 this issue was not there .

DD-WRT make progress in that direction I belive we need to modify image headers, to match routers version

So I have to install DD-WRT
and then install Openwrt with DD-WRT to OPEN-WRT

or there is some other way in which i can modify headers of openwrt image , where to do that changes.

Read their post need to log to see the file http://www.dd-wrt.com/phpBB2/viewtopic.php?t=279582

I referred that link and did this ,

I installed ddwrt beta image available for TP Link 740n version 5

then I installed openwrt with following command
Don't know why but this command is not working now and my one router got bricked
I don't recommend doing this

mtd -r write openwrt_squashfs_sysupgrade.bin linux

It will work for now, but there must be way to directly install openwrt on TP-LINK 740n

(Last edited by vrdvaibhav on 27 Oct 2015, 13:15)

I wonder if OpenWrt development team, notice that there is version 5 for supporting.

Hello guys, here's the FW for 740N/ND v5 (non-chinese) with Luci:

Factory:
https://www.dropbox.com/s/qil9yq35n127u … y.bin?dl=0

Sysupgrade:
https://www.dropbox.com/s/l2l853k32d1d2 … e.bin?dl=0

TP-Link WR740N v4 Int and v5 int are different in 3 aspects:
- Missing the on/off switch in V5. The construction of the PCB is much lighter, and much more intolerant to high/low voltages
- The LAN ports are turned upside down, with the RJ clip up.
- The reset button is no longer a pin hole

Apart from this everything else is the same.

Now about the firmware.
V5 have some more pluses over the V4. It have a page showing username/password fields, and dropbear running on port 22. However having dropbear does not mean that one is able to login to console session.
The username and the password are the same as the one which the user should input on the login page (default is admin/admin), however the PTYs are mistaken:
The reply from the dropbear is as follows:

PTY allocation request failed on channel 0
shell request failed on channel 0

If you modify the firmware and add telnet server, you'll be able to gain shell access by using username root and password sohoadmin. No worries about the free space. the original firmware is around 2MB large.

Flashing from Stock V5 to Stock V4 and vice versa could be made from the console, or from the httpd application.
If you're using the httpd app, then the header of the firmware you want to write should contains 3 fields:
- hardware version, found on offset 0x40 and contains 07400005 for V5 and 07400004 for V4
- firmware version, found on offset 0x44 and contains 00000001 aways
- firmware checksum, found on offset 0x4C checked by httpd and by bootloader.

As you can see if you are running the stock bootloader you're no go without a correct checksum.
This issue is resolved by two means:
- custom bootloader - try pepe2k one's. I am using it since a long time and it is very good peace of software
- checksum calculator

In order to gain access to the bootloader you might try to flash DD-WRT and then to rewrite the mtd0 with the pepe2k one's. However do not forget to make a backup.

If you're using checksum calculator, it is straight forward process. Change the HW version and you'll have a new strings inside the firmware file and a new checksum as well.
Then you might proceed with the flashing via httpd

can you please tell us how did you generated those images,
I think we need to change headers but don't know much about it.
your images are OpenWRT 14.07, and I want to generate images for 12.09 version.