Friday, September 25, 2009

Serial RS-232 on WRT54G2

Last night, I had created a very simple yet workable RS-232 to my pc for viewing the output while the wireless router is booting up.

Well, at first I was using MAX232 which I savage out from my old electronic projects. I thought of lazy to get a new one from Pasar Road (KL). But, the sad thing was I accidentally broken it and I have to think of another way quickly. I need to see the output in order to know what was happenning to my firmware on this wireless router. It was not booting up properly. As I am still very new to this wireless router and also I am new in writting firmware for this particular wireless router.

In fact I was out of idea, then when I saw some of my spare transistors lying around then it strikes me to use the olden days technology. Which using only NPN transistor getting the output from the wireless router RS-232 port signal. It just need to amplify the signal in order to feed to the serial port of the PC.

I was googling around and search for "Transistor MAX232" and I found this. The below image is the one that I found from the net.

Well, for display output of the wireless router purposes, we just need the upper part of the schemetic. Guess what? It works!! But of course, if you need a full-duplex RS-232 will need both. In the future post, I will show you how am I going to use the MAX232 for turning this wireless router to a capable reading data from the RS232 port.

Now, I realized that my firmware was not an issue. It was the CFE (Common Firmware Enviroment) which was using the previous version for the DD-WRT. No wonder no matter how I tweak my firmware which is the OpenWRT and it does not run at all.

So, next post will be going to explain more details about how to flash the CFE using JTAG (Home made JTAG which costs $0).

References:
http://melbourne.wireless.org.au/files/wrt54/cfe.pdf
https://wiki.openwrt.org/oldwiki/openwrtdocs/customizing/firmware/cfe
http://www.circuitlake.com/simple-rs-232-level-converter.html

1 comment:

0x7B3 said...

Could you provide photos of PCB serial pinouts. AFAIK there are only pads under green solder mask.