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From: carolyn@cbmvax.commodore.com (Carolyn Scheppner - CATS)
Newsgroups: comp.sys.amiga.programmer,comp.sys.amiga.hardware
Subject: Re: I *STILL* need help with the POTGO resource!
Message-ID: <22264@cbmvax.commodore.com>
Date: 8 Jun 91 00:34:10 GMT
References: <-J#-M6C@engin.umich.edu>
Reply-To: carolyn@cbmvax.commodore.com (Carolyn Scheppner - CATS)
Organization: Commodore, West Chester, PA
Lines: 122

In article <-J#-M6C@engin.umich.edu> chymes@uri.csmil.umich.edu (Charles Hymes) writes:
>I use basically the following lines to set up the POTGO resource.
>[]
>I tried other code as well, but the values at pot1dat never change no
>matter what I do at the gameport. If I connect pins 5 or 9 to (the X
>and Y pot pins) to pins 7 or 8 (+5 volts and Ground respectively)
>Nothing changes at pot1dat.
>Potinp changes the way you would expect it to, but I don't want on/off
>values, I want the 8-bit values one expects from the Pots.
>
>The (old white A1000) Hardware manual says that Potgo needs to be
>reset each vertical blank, but it also says that that is taken care of
>by the OS. Is this shut off when I use the POTGO resource?

I think the HW manual says you have to EITHER read it during vertical
blank OR read it twice.

Meanwhile, here's an old piece of Phil Lindsay code that does use
vertical blank (little piece of asm at end)

potgo.c
/* potgo.c - read right port's x, y pots
 *	Remember to use options +lcd for MANX Aztec C (longs & A4 dependency)
 */
#include <exec/types.h>
#include <hardware/cia.h>
#include <hardware/intbits.h>
#include <exec/interrupts.h>
#include <resources/potgo.h>
#include <libraries/dos.h>

/* macro functions to grab pot x and y from pot1dat */
#define POTX(x)		((x) & 0x00ff)
#define POTY(y)        	((y) >> 8)

/* hard addresses for potgo and pot1dat */
#define POTGO		0xdff034
#define POT1DAT		0xdff014

/* vertical blank interrupt server priority   */
#define MYINTPRI	10L 	/* my priority is 10 higher than gamedev intr */

#define START_B		0	/* bit number defines for potgo ... */
#define DATRX_B		12	
#define DATRY_B		14
#define START_F		(1L << START_B)	/* masks ... */
#define DATRX_F		(1L << DATRX_B)
#define DATRY_F		(1L << DATRY_B)	

#define RPOTXY		(START_F | DATRX_F | DATRY_F) 

long	PotgoBase;	/* resource base */
UWORD 	potxy;		/* global for pot1dat storage */

extern void getpot(); 		/* vert. blank interrupt routine */

main()
{ 

 long  alloc;
 struct Interrupt myintr;

 PotgoBase = (long) OpenResource(POTGONAME);

 alloc = (long) AllocPotBits(RPOTXY);

 printf("Allocated: %lx\n",alloc);

 if(alloc != RPOTXY)
   {
    puts("Couldn't get potgo bits.");	
    FreePotBits(alloc);
    exit(TRUE);
   }		

/* intialize interrupt structure */
 setmem(&myintr,(long)sizeof(myintr),0L);
 myintr.is_Node.ln_Pri  = MYINTPRI;
 myintr.is_Data         = POT1DAT;
 myintr.is_Code         = getpot;
 
 AddIntServer(INTB_VERTB,&myintr);

/* loop while !ctrl-c */
 while(! (((ULONG)SetSignal(NULL,NULL)) & SIGBREAKF_CTRL_C) )
   printf("x=%ld, y=%ld\n",(long)POTX(potxy),(long)POTY(potxy));
 
 RemIntServer(INTB_VERTB,&myintr);

 FreePotBits(alloc); 

}

/* eof */
******************************************************************************
potgoint.asm
* Vertical Blank Interrupt Server code.

	xref	_PotgoBase		* get potgo resource base
	xref	_potxy			* global storage for pot1dat
        xref 	_LVOWritePotgo		* resource routine to write potgo

	xdef	_getpot
_getpot:
        move.w	(a1),_potxy 		* a1 points to pot1dat
	move.l 	_PotgoBase,a6 		* move resource base into a6
	move.l 	#1,d0			* potgo start bit = 1
	move.l	d0,d1 			* our mask is 1
	jsr 	_LVOWritePotgo(a6)	* call write potgo
	move.l #0,d0			* cont interrupt chain
	rts				* gone...
	end
* EOF


-- 
==========================================================================
 Carolyn Scheppner -- Tech. Mgr. CATS - Commodore Amiga Technical Support
 PHONE 215-431-9180 {uunet,rutgers}!cbmvax!carolyn  carolyn@commodore.com

 Integer math - it's all so pointless.
==========================================================================