So I recently puchased a TP-link MR6400 for using OpenWRT.
the hardware is apparently at v3, while v1 is supported, v3 is not. i tried flashing the version for the v1, but that did not work. now the unit is "flashing on all led's".
I can still trigger u-boot tftp recovery. but i do not have the recovery image for this device. does anyone know how to get this from the tp-link firmware file?
FYI, the device will try to download "tp_recovery.bin" via tftp from 192.168.0.225, when holding the reset button for at least 5sec while powering on.
I tried using the official firmware renamed as "tp_recovery.bin" and served it over tftp, but does not seem to work (still blinking LED's). as for the other guide, it would require me to have a valid .bin file. which i currently do not.
I have not started to look for a UART yet.
After messing around with openwrt on my MR6400 and not being able to get the 4g modem to work, I decided to go back and had the same problem as the OP, tftping the factory tplink firmware does not work. Further investigation reveals that tplink have stuffed 512 bytes of garbage at the beginning of their firmware which needs to be chopped off before it will work.