Subject: [stella] Paddle controller docs? From: "C. Bond" <cbond@xxxxxxxxxxxxx> Date: Tue, 17 May 2005 11:59:01 -0400 |
I haven't been able to locate any comprehensive docs about the VCS paddles online, although there are bits of information here and there, including the info in the Stella Programmer's Guide. Here is what I'm looking for: 1) Is there a schematic of the electrical circuit for the paddles, including component values? (I know that a capacitor is charged at a rate depending on the position of the variable resistor controlled by the knob, and that a Schmitt trigger is activated when the capacitor voltage exceeds its threshhold. But have not been able to find the time constants or component values anywhere.) 2) What is the approximate minimum and maximum delay times from the start of charge to the activation of INPT0? (or INPT1, INPT2, etc.) 3) What is the best way to interrogate the paddles? Apparently it is expected that the capacitors will be discharged and clamped to ground by writing 1xxx xxx (binary) to VBLANK, and that the charging process can begin when the capacitor is unclamped by writing 0xxx xxx to VBLANK. But should the timer be used to measure the delay? Is it sufficient to count scan lines? That is, VBLANK <- 1xxx xxx ; discharge capacitors ... ... VBLANK <- 0xxx xxx; unclamp capacitors ??? ??? ??? LOOP: LDA INPT0 BPL LOOP ??? ??? ; how do I determine the elapsed time? ??? I tried to figure out the method used in BREAKOUT by examining the code, but got lost! 4) What is a good way to use the keyboard to emulate a paddle? Clearly the LEFT and RIGHT cursor keys can be used to increment or decrement a number which could represent the paddle position, but what are the normal paddle limits and how do I guarantee that the software will accept the emulation? Thanks for any pointers. C. Bond -- Democracy: The triumph of popularity over principle. -- http://www.crbond.com Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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