Subject: Re: [stella] need some quick software help... From: emooney@xxxxxxxxxxxxxxxx (Erik Mooney) Date: Thu, 08 Jul 1999 04:03:10 GMT |
>I'm playing with a couple of projects (yes Glenn, I *know* I should be >working on the Superchip board! :) and I need some Quick&Dirty Code(tm) >to send a square wave out the joystick port. Does anyone have a code >snippet that does this? Or that simply sends out *anything*? Maybe >for the keypad controller? > >I know this is pretty easy to do, but I don't have time to re-invent the >wheel. :) Actually, this fits in nicely with the recently discussed >networking project... Okay, took me about 4 minutes :) Here's the code.. I'll email a binary to Chris separately. If someone sees a problem here, lemme know. It should generate a square wave on all four directional lines of both joysticks, at about 1 KHz. (there's 8 WSYNCs for each half-cycle, and the Atari scans at something like 15.8 KHz IIRC.) It's untested, of course, but it seems too simple to fail. (Yes, Nick, those are still your comments way back from How to Draw a Playfield, which I still use as a skeleton for my code) include vcs2600.h org $F000 ;RAM locations Start SEI ; Disable interrupts, if there are any. CLD ; Clear BCD math bit. LDX #$FF TXS ; Set stack to top of RAM. LDA #0 ;Zero everything except VSYNC. B1 STA 0,X DEX BNE B1 DEX STX SWACNT ;set data direction registers to output STX SWBCNT bigloop LDA #$FF STA SWCHA STA SWCHB STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC LDA #$00 STA SWCHA STA SWCHB STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC STA WSYNC jmp bigloop ;Starting positions for PC org $FFFC .word Start .word Start -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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