Sega Genesis controller on PS2?

Do I need to attach a wire for each button on the Genesis and PS1 controllers, or is there a painless way that won't require butchering the controller/cables?

I have a 3-button, and here's my mapping:

Up = up
down= down
left = left
right = right
start = start
a = x
b = o
c = triangle

(Just because, I paid $4 for the Genesis controller, and $2-4 for the PS1 one. (I bought it a loooooooong time ago.))

 

The project started, had to rewire the whole thing.

 

PSX controllers use a SPI protocol running at 250 KHz with the added ACK line. Genesis controller on the other hand is not a serial device at all.
It uses a 9 pin connector and each "button dedicated wire" corresponds to two buttons. State of the line (high, low) determines if button is pressed.
To choose between a 1st and 2nd button console manipulates a "select" line. It's pretty basic stuff actually compared to the other controllers on the market.

There are two options:
1. Rewire the whole thing like you did.
2. Build a converter which would act as a SPI slave to PSX and would transfer Genesis' controller button state to serial data PSX expects.

Do note that not all PS2 games will accept a PS1 controller.

 

Protocol converter is required or you can put the PSX/PS2 joypad chip into genesis joypad shell,and rewire all button.