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Home-Made JTAG Cable

In order to get into the router to program the flash or debug the kernel, you need some simple JTAG Cable.

First of all, you need to solder the JTAG connection by yourself because the router didn't come with it soldered. It was a little bit tough because I had to remove the solder from the soldering pad so that I can put the connector on. Using a air-sucking desolder, it's actually not a very hard job.

Then I just downloaded some schmeticas from and home-made one WIGGLER compatible JTAG Cable.

I didn't 100% follow the schematics because I don't really have AC244 in hand and I don't want to use the transister to make the reverse logic. So what I did was to use a GAL20V8 instead and program the logic to be really simple pass though or inverted. Of course you wonder GAL20V8 is a 5V device and why should I use it on the 3.3V system. Well, it's just home-made and I looked though the datasheet of GAL20V8 and it seems like 3.3V should also work. At least it'll not break anything.


Serial Interface

No surprice that the router comes with a serial connector on board. But again, not solder. So I had to do the same trick as the JTAG.

The pins on the connector are connected to the S3C4510 CPU directly so it's gonna be 3.3V logic. Well, I did something tricky again that I just used a MAX232A to do the level convertion. One thing to remember is that you'd better bring power to the MAX232A from the router board. I just brought the 3.3V from the voltage regulator U15(APL1085) and it works perfectly.

Some pictures of my home-made hardware

My router board with JTAG and Serial cable attached:

Serial and Jtag cable:

Enlarged Serial Cable:

© 2005 Zibo Zhao | Last update: 2/23/2005