Plugin mini usb to the jtag adaptor and plug the adaptor to pc’s LPT port.
I use win7 and the software is from http://sourceforge.net/projects/tjtag/files/
I always use these switches for rt-n16: /noreset /nodma /byte_mode
For my case, it is easy. I only want to fix the nvram entry I messed up. I backup nvram and use hex editor and change clkfreq to the right value, and flash it back. My trusted rt-n16 is back. ^_~
Hope this is helpful for anyone who may decide to use jtag before trying replace NAND chip.
Got adaptor from diygadget and just recovered it last night. I'll update the wiki when I'm home. Overall, it's a fairly easy process if you are comfortable with soldering a few pins on the PCB. And the buffered jtag makes the process easier with long cable.
I can now mess up this router really good (or bad) with this Jtag insurance policy as long as I do not physically damage the router.
Thanks guys for guiding me through this.
Congrats.. I can't find the "like" button but if we had one....
The reason I'd like to restore the modified Nvram is because that I do not have a recent backup, I am very lazy to go through the manually setup for VPN firewall rule and other things, Should have done the nvram backup more frequently.
BTW, the wiring diagram is wonderful.
@goldbeanchina: Congratulations on restoring your router.
I repeated your clkfreq experiment and found an easier and much faster way to recover. (JTAG flashing a 128KB NVRAM file requires about 1 hour and 54 minutes.)
Here's what worked for me:
At a command line prompt enter: tjtag3 -erase:nvram /byte_mode <=== Executes in 1 second!
Power cycle the router which causes the CFE to restore default values (i.e. clkfreq=480,240,120) to the NVRAM partition and allows the router to successfully boot.
Use the router's WebGUI to restore a good, previously saved config file.
Here's a helpful wiring diagram for the TIAO Version 2 Universal JTAG PCB: (Click on image to make bigger in a new browser tab)
Well I was lead here when my RT-N16 was bricked and couldn't be recovered. I am a little confused. I just bought this on eBay, but it doesn't look like this can be used to JTAG a router (this is my first time having to JTAG):