A few days ago a friend send me an old mobile phone for using in a project about weather information in a remote location.

On the internet I found which pins on telephone are TX, RX, GND. I simply connected them to USB -> RS232 cable, when I found out that I must destroyed it last time by shortcut between ground and 5V.

I remembered about a project in which author used V-USB firmware only implementation of USB fot AVR devices to create home made USB to RS232 converter. In a few minutes I had a working converter (Thanks toOsamu Tamura at Recursion Co., Ltd.)
I connected everything and result was ... garbage. On HyperTerminal I received only garbage. I remember about using MAX232 chip for converting TTL levels to computer levels and vice versa. Tried with this chip and the same thing, of course a little bit different garbage, but still garbage and nothing useful.
So I give up for today ... tomorrow is a new day and maybe I'll have more luck. I could try connecting AVR with code for serial communicating to see if there is a problem on converter/computer or somewhere else.