I recently made a quick and dirty adapter for converting Master System-controller to MSX-controller using a cheap de-9 extension cable from AliExpress.
Please note that this is ONLY for using Master System-controllers on MSX. Don't try this with MD-controller since you will probably break your MSX doing so - there are other, more advanced adapters for using MD-controllers out there.
Unlike the Mega Drive controller, the Master System controller doesn't contain any active parts that can damage the MSX, but without adapter, only button 1 can be used. The difference is that the Master System has button 2 connected to pin 9 (gnd on MSX, so nothing happens when pressed).
To make button 2 work, you only need to take the cable that goes to pin 9, and connect it to pin 7 instead. You can make the cable that was connected to pin 7 go to pin 9 instead or just not connect it at all, since it's not used by the Master System controller anyway.
I still wanted both MS-controller and extension cord still work to my Master System, my C64 and my Amiga 500, so I installed a simple switch on my cord, but that is optional.
I started with cutting up half of the exterior of the cable. Next is to locate which wire goes to which pins. I had recently cut up 4 other of these newly produced extension cables from AliExpress and a local shop (that probably got them from the same place) and the color coding was the same in all of them. So I began cutting away a little bit of the rubber from the white and yellow cords to test with MultiMeter to the pins - and they were the correct ones in this one too! (goes to pin 7 and 9, can't remember which is which though)
Then all you need to do is cross connect them and wrap it up. Done! Both buttons working on MSX!
Hope this info can be of use for somebody out there :-)
