I uploaded a bad firmware to my router and now the power led became red.
I opened the router and connected the pins of en internal serial port to my computer's serial port with a ttl-rs232 adapter. I established a 115200-8-N-1 connection to the serial port with GtkTerm, powered up the router and got the cfe prompt, but I cannot enter anny command.
I also tried to use tftp to upload a new formware, but without success.

Is there some way to unbrick the router?