reverse engineer 8 bit tv game joystick

need help to reverse engineer victor 8 bit tv game joystick ... it looks like ....... it also has select button along with start....its using db9....pins 2 3 4 7 9 ....anyone with any info on this plz share...

It’s a D-pad, not a joystick.
What exactly do you want to reverse engineer, the button layout? Or are you looking for a library that allows you to connect to the arduino and see the button data?

If it’s a library you want, I would say check the playground, but it does not seem to be accessible, at least not on my end.

Update: the chip used in the Sega, NES and SNES was the CMOS 4021 8bit shift register. Basically if a button(s) was pressed, it would be converted to a byte and sent through the data line. I’m not sure about the clock rate though.