Potgo Resource

The potgo resource is used to get control of the hardware POTGO register connected to the proportional I/O pins on the game controller ports. There are two registers, POTGO (write-only) and POTINP (read-only). These pins could also be used for digital I/O.

The potgo resource provides three functions for working with the POTGO hardware.

Potgo Resource Functions

AllocPotBits()	Allocate bits in the POTGO register.
FreePotBits()	Free previously allocated bits in the POTGO register.
WritePotgo()	Set and clear bits in the POTGO register. The bits must have been allocated before calling this function.

The example program shown below demonstrates how to use the ptogo resource to track mouse button presses on port 1.

/*
 * Read_Potinp.c
 *
 * An example of using the potgo.resource to read pins 9 and 5 of
 * port 1 (the non-mouse port).  This bypasses the gameport.device.
 * When the right or middle button on a mouse plugged into port 1 is pressed,
 * the read value will change.
 *
 * Use of port 0 (mouse) is unaffected.
 *
 * Compile with SAS C 5.10  lc -b1 -cfistq -v -y -L
 *
 * Run from CLI only
 */

#include <exec/types.h>
#include <exec/memory.h>
#include <dos/dos.h>
#include <resources/potgo.h>
#include <hardware/custom.h>

#include <clib/exec_protos.h>
#include <clib/potgo_protos.h>

#include <stdio.h>

#ifdef LATTICE
int CXBRK(void) {return(0);}  /* Disable SAS Ctrl-C checking */
int chkabort(void) { return(0); }  /* really */
#endif

struct PotgoBase *PotgoBase;
ULONG potbits;
UWORD value;

#define UNLESS(x) if(!(x))
#define UNTIL(x)  while(!(x))

#define OUTRY 1L<<15
#define DATRY 1L<<14
#define OUTRX 1L<<13
#define DATRX 1L<<12

extern struct Custom far custom;

void main(int argc,char **argv)
{
UNLESS (PotgoBase=(struct PotgoBase *)OpenResource("potgo.resource"))
        return;

potbits=AllocPotBits(OUTRY|DATRY|OUTRX|DATRX);

/* Get the bits for the right and middle mouse buttons on the alternate mouse port. */

if (potbits != (OUTRY|DATRY|OUTRX|DATRX))
    {
    printf("Pot bits are already allocated! %lx\n",potbits);
    FreePotBits(potbits);
    return;
    }

/* Set all ones in the register (masked by potbits) */
WritePotgo(0xFFFFFFFFL,potbits);

printf("\nPlug a mouse into the second port.  This program will indicate when\n");
printf("the right or middle button (if the mouse is so equipped) is pressed.\n");
printf("Stop the program with Control-C. Press return now to begin.\n");

getchar();

UNTIL (SIGBREAKF_CTRL_C & SetSignal(0L,0L))
      /* until CTRL-C is pressed */
      {
      /* Read word at $DFF016 */
        value = custom.potinp;

      /* Show what was read (restricted to our allocated bits) */
      printf("POTINP = $%lx\n",value & potbits);
      }

FreePotBits(potbits);
}

Additional programming information on the potgo resource can be found in the include files and the Autodocs for the potgo resource.

Potgo Resource Information
Includes & resources/potgo.h
& resources/potgo.i
& utility/hooks.h
& utility/hooks.i
AutoDocs & potgo.doc