Unbrick TP-Link WR941ND

I got a bricked TP-Link WR941ND. with open-wrt installed. The owner made a mistake in the configuration of the dhcp server on the router. As a result there is no way to get access on the device.

Informations for openwrt on the WR941ND: http://wiki.openwrt.org/toh/tp-link/tl-wr941nd

I tried the failsafe and the router blinked as described in the wiki. But I got no access to the router. The last remaining option is sending serial data to the router via JTAG. But first problem was opening the router. This youtube video helped: https://www.youtube.com/watch?v=sxVP7WGzH_A

To simplify the connection 4 pins were soldered onto the router board. (add picture)

ardunio solution: https://forum.openwrt.org/viewtopic.php?pid=191463