Years ago I dissasembled a tandy colour computer game that had a light gun. I stole the routines that got the gun x,y and made my own game.
I know I could get the gun x,y, but I had to flash the whole screen white, then call this code. There was also some variation between samples. (about 5 pixels in both axis)
I think the code did some stuff with the vertical retrace flag. I also believe the code did the vertical by counting from the vertical retrace, and the hardware did the horizontal, maybe with a phased locked loop watching the raster. If I still had all that stuff, I'd get a hardware dude at work to analyse it with a cro etc.
BTW It was a Sega 'light phaser' with some custom box the game company (diecom) made. A very cool looking gun!
Slashdot Mirror
I know I could get the gun x,y, but I had to flash the whole screen white, then call this code. There was also some variation between samples. (about 5 pixels in both axis)
I think the code did some stuff with the vertical retrace flag. I also believe the code did the vertical by counting from the vertical retrace, and the hardware did the horizontal, maybe with a phased locked loop watching the raster. If I still had all that stuff, I'd get a hardware dude at work to analyse it with a cro etc.
BTW It was a Sega 'light phaser' with some custom box the game company (diecom) made. A very cool looking gun!