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Flashing TP-Link WR841N router with DD-WRT

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soldar:
I picked up from the street a TP-Link WR841N(TPD) Ver 9.0 router. It seems it has some proprietary software from some company that used it to sell services to public places, like restaurants, so customers could use free wifi in exchange for advertising.

The router is configured at 172.16.0.1, 255.255.0.0 and I can connect to it there both by ethernet and by wifi. It responds to ping but when I try with the browser and http I just get a text error message

--- Quote ---Unable to launch the requested Lua program:
  /root/gestorConexiones.lua: /root/gestorConexiones.lua:163: attempt to concatenate global 'promotionId' (a nil value)
--- End quote ---

It seems "lua" is some simple programming language from Brazil. I am guessing the device is trying to call home before even getting started.

With this software it is useless to me and I thought of flashing it with DD-WRT.  Last time I attempted to flash a router I bricked it. In this case it would not be a great loss because it is pretty much useless as it is and because I am doing this for fun. I have more routers than I can use. So let us have a look a possible ways to flash this thing.

1- HTTP & Ethernet. As explained above there is no configuration page I can access. Unless someone has a better idea this seems like a dead end. To use this the router needs to cooperate and it is not.

2- JTAG. The board seems to have a JTAG connector ready to accept a header. I have never used JTAG. Reading about it it seems it uses the old printer parallel port. This seems cumbersome and I think I would rather avoid going this route.

3- USB Next to the JTAG there is a four pin place for a header which I interpret as USB. I wonder about trying this but I suspect it depends on the current firmware supporting it and it probably does not so it is like http & Ethernet. Probably no-go.

4- Removing/desoldering the Flash chip and having someone flash it for me because I do not have the means or inclination to do it. The chip is an 8 pin SMD mx25L3206 which I gather is 32 K bit. Being SMD I would need to be extremely careful but this seems like the most straightforward route to me if i can find someone who can flash the memory chip for me.

5- Other? Return it to the trash?

I guess, in the worst of cases, I can always use it as a switch using the four LAN ports. It does work with the 192.168.x.x LAN. Although the WIFI is on and useless then. Hmmm....

retiredcaps:
Did you try the hardware reset?

https://www.tp-link.com/ca/support/faq/497/?utm_medium=select-local

https://reset-routers.com/routers/hard-reset-tplink-tlwr841nd/

retiredcaps:
It looks like this device is 4MB flash 32MB DRAM.  I have a lot of "free" wi-fi routers in this range.

With it, you can choose dd-wrt or openwrt.  I find openwrt less buggy than dd-wrt.  For example, using dd-wrt, I found that simple things like

echo foo > /tmp/test

doesn't work on the K26 build for a Cisco/Linksys router.  No problems with openwrt on the same router.

I'm using a Dlink dir-615 c1 right now, but I found on dd-wrt, that the 2.4Ghz radio would stop responding after a couple of hours to a couple of days.  No problems with openwrt on the exact same router.

With either, I have enabled a simple script to add a hosts file for some ad-blocking at the router level.

On some of my other Cisco/Linksys routers, I HAVE to use dd-wrt because it contains the broadcom proprietary blobs to make 802.11n work.  Openwrt uses open source code and it doesn't support 802.11n speeds with the broadcom chipset.

tunk:
https://openwrt.org/toh/tp-link/tl-wr841nd

I had a 841v8 which I bricked and IIRC I used TFTP (with network cable) to unbrick it.
Pt. 3: This most likely is 3.3V TTL serial (not RS232).

retiredcaps:
I should say that openwrt, like all software, isn't perfect either.

I have a Cisco/Linksys E2000 that was running openwrt 17 fine.  I decided to upgrade to 18.0 and the 18.0 software bricked the E2000.  :--

I haven't yet tried to unbrick using a serial to USB jig.  It's a very low priority given how many "free" wifi routers I have as a backup.  I just hate seeing still useful equipment go to waste.

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