USB adaptor for Amiga Joysticks
 

Hi guys!

as the title says, I would like to build an adaptor that converts the DB9 port to an USB in order to use the good old amiga joysticks. I've found this thread which is very very relevant to this purpose but it seems to me that it is a little bit old therefore I decided to start a new one (hope that it is a good choice). The aforementioned thread gave me a lot of precious information and ideas but there are still some points that are not clear to me. In particular, being a beginner, I would like to ask you what GND (ground) exactly is, which is the function of the GND wire and how I can recognize the right area in a PCB that I should use to solder the GND wire. Furthermore my objective is to build an adapter for the Albatros joystick (a popular joystick built for Amiga) and that joystick had two buttons that made the same thing. Should I solder two wires (button1 and button2) on the same place of the PCB or it is sufficient to solder only one wire that (maybe?) controls both the buttons? Eventually I have some questions that are expressed in this image
http://img809.imageshack.us/f/14747660.png/
http://img809.imageshack.us/f/14747660.png/
thank you very much in advance!

FYI:

http://www.retrousb.com/product_info...products_id=70
http://www.raphnet.net/electronique/...b/index_en.php
http://www.vilminko.net/henri/projvi...?id=19&lang=en

thank you alexh for your pointers, especially the last one is very interesting. Anyways still it is not clear to me which are the answers to my questions!

Ground is a zero-volt. For want of a better analogy consider it to be the negative terminal of a battery. Use a multi-meter in continuity mode and connect the GND wire to one probe and touch large areas of metal and chances are that is GND too.

One wire.

Erm, to do what? Buttons are switches, they have three terminals and if you want to "extract" the state of the switch you solder to two of them. (Maybe one depending on your design)

I'm sure it is lots of places. Why does it matter that GND is there?

Thank you very much alexh! Now things are clearer..if I have other doubts I will ask here for new info