/*****************************************************************************
 *                          MODULE: SAMPLE8.C                                *
 *                                                                           *
 *  This sample program will sequentially turn on all bits in port a and then*
 *  seqentially turn them off.  Each time it sets a new bit, both port a and *
 *  port b are read and the data displayed.  This demonstartaes how to read  *
 *  and write to a port, and to use the read back function of the 8255 chip. *
 *  If the port a pins are jumpered to the port b pins, then a board test    *
 *  program results, with port b being used to verify what has been written  *
 *  to port a.  The program will use port 0 of cards with mulitple 8255's.   *
 *                                                                           *
 *****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <dos.h>

unsigned int Address; // assign Base Address to variable

// this typedef allow use to duplicate the boolean type as used in pascal

typedef enum {FALSE,TRUE} boolean;


unsigned AskForBaseAddress(unsigned int OldOne)
{
	char msg[7];
	int NewOne = 0, Success = 0, Dummy;
	int AddrInputPosX, AddrInputPosY;

	puts("\nPlease enter the Base Address for your card (in hex)");
	printf("or press ENTER for %X.\n>", OldOne);
	AddrInputPosX = wherex(); AddrInputPosY = wherey();
	do {
		gotoxy(AddrInputPosX, AddrInputPosY);
		clreol();
		msg[0] = 5; msg[1] = 0;
		cgets(msg);
		sscanf(msg + 2, "%x", &NewOne);
		Success = 1;
      Dummy = NewOne;
		if (msg[1] == 0) {
			gotoxy(AddrInputPosX, AddrInputPosY);
			printf("%X", OldOne);
			Success = 1;
			Dummy = OldOne;
		}
	} while(!Success);
	return (Dummy);
} // end of AskForBaseAddress

/*****************************************************************************
 *  FUNCTION: signon -- local routine                                        *
 *   PURPOSE: To display an initial sign on message on the screen.           *
 *****************************************************************************/
void signon(void)
{
   int	index;

   // print the string display and ask for the base address
   clrscr();
   puts("                     8255 Digital I/O Sample Program \n"
        "This sample program will sequentially turn on all bits in port a and then\n"
        "seqencially turn them off.  Each time it sets a new bit, both port a and\n"
        "port b are read and the data displayed.  This demonstrates how to read\n"
        "and write to a port, and to use the read back function of the 8255 chip.\n"
        "If the port a pins are jumpered to the port b pins, then a board test\n"
        "program results, with port b being used to verify what has been written\n"
        "to port a.  The program will use port 0 of cards with mulitple 8255's.\n"
       );
   Address=AskForBaseAddress(0x300);
   puts("\nBoard Configuration:\n");
   printf(" -- Base Address is %X hex\n",Address);
   printf("Connect a loopback cable from PORT A to PORT B of PPI0. (required)\n");
   printf(" PRESS ANY KEY TO CONTINUE");
   getch ();
   clrscr();
   gotoxy(1,6);
   printf(" PORT A OUTPUT     PORT A INPUT      PORT B INPUT \n"
          " -------------     ------------      ------------ \n"
         );
   gotoxy(1,10);
   printf(" PRESS ANY KEY TO EXIT PROGRAM ");
} // end signon

/*****************************************************************************
 *  FUNCTION: write_port_data -- local routine                               *
 *   PURPOSE: Displays the current port values on the screen.                *
 *****************************************************************************/
void write_port_data(unsigned char current[3])
{
   unsigned      x,y,index1,index;
   unsigned char value;

   x = 4;    // x coordinate to write value to screen
   y = 8;
   for (index = 0;index <= 2;index++)       // for each array member
      {
      value = current[index];
      for (index1 = 0;index1 <= 7;index1++) // for each bit in array member
         {
         gotoxy(x,y);
         if (value % 2) putchar('1');
         else putchar('0');
         value = value >> 1;                // roll next diaplay bit
         x++;
         }
      x+= 10;
      }
}  // end write_port_data

/*****************************************************************************
 *  FUNCTION: main -- external routine                                       *
 *****************************************************************************/
void main()
{
   unsigned char    current[3];
   boolean	        shift_left;

   signon();                          // print the start up message
   outportb(Address+19,0x8b);        // send the control byte for A out B in
   outportb(Address + 0x18, 1);
   current[0] = 0;
   shift_left = TRUE;
   while(!kbhit())                    // loop until key pressed
      {
      outportb(Address+0x10,current[0]);     // write value to port a
      delay(10);
      current[1] = inportb(Address+0x10);    // read back what we wrote to port A
      current[2] = inportb(Address+0x11);    // read the data on port B
      write_port_data(current);       // write new data to screen
      delay(700);

      // compute value to turn on/off nesxt bit in line
      if (current[0] == 0) shift_left = TRUE;
      if (current[0] == 255) shift_left = FALSE;
      if (shift_left) current[0] = (current[0] << 1) + 1;
      else current[0] = (current[0] - 1) >> 1;
      };
   clrscr();
} // end main program