This is a tale of how someone remembered that he had a non-functional router, in this case an older Linksys WRT54G, and…
… decided he would have a go at repairing this ancient router. There was only one problem: the most popular utility for programming the router through the JTAG header required a PC parallel port.
Unfortunately, parallel ports are becoming as hard to find as floppy disk drives these days, but did that deter him? No way, he simply added Raspberry Pi support to the debricking utility, and used the Raspberry Pi’s GPIO pins to do the job. Unfortunately, in the end he was unsuccessful, but only because he physically damaged the circuity on the router while attempting to upgrade the RAM – had he not attempted the hardware modification, this likely would have worked. So, although we make no guarantees, if you have a bricked router, read the articles linked below and maybe you can bring it back to life.
Unbricking a Router With a Raspi (Hack A Day)
Debrick WRT54GL using Raspberry Pi (JTAG bit banging) (Oxblog)