Subject: Re: [stella] a "pot" of confusion From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx> Date: Wed, 26 May 1999 14:28:28 +0200 |
At 23:12 25.05.99 -0700, you wrote: >after looking over the stella document some more, i noticed that the four paddles >only have one bit each in which the pot can be read...and i find that >confusing...how >does one go about keeping track of where the knob of the paddle is and stuff? You count the time that it takes for the paddle bit to go from low to high. When you write a 1 into bit 7 of VBLANK the pots will be discharged and the paddle read bits will go low. When you write 0 into bit 7 of VBLANK the pots will start to recharge. The further you have turned a paddle's knob the longer it will take to recharge the paddle's pot and the longer it will take the paddle's read bit to go high again. Usually you do the discharge/start the recharge stuff during the VSYNC time. Then you have to set a counter in RAM to zero. During the displayed part of the screen you read the paddle bit in every scanline and if it still is low, you increase the counter by one. At the start of the overscan the counter then holds a value, that you can use to position your player or whatever. Ciao, Eckhard Stolberg -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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