Reading Driving Controller Atari 7800 Basic

[peteym5]

Does anybody know how the driving controller is suppose to work in Atari 7800 Basic? I tried it, it seems like it is only reading going left. I am not sure this is suppose to read the Indy 500 controller, or some other type of steering wheel type device that plugs into the DB9 port.

 

[RickR]

I'm not sure what the specifics of Atari 7800 are, but you have to write a "Gray code" interpreter for those driving controllers.  If you're only reading one direction, I suspect you aren't polling often enough.

https://en.wikipedia.org/wiki/Gray_code

 

[peteym5]

I suspect it might be an issue with 7800 Basic built in driving controller routine. I have written ML driving controller routines for the Atari 8-bit that I can just port over.