/****************************************************************************
 *  This sample will prompt the user for a voltage between 0 and 10 volts,  *
 *  then calculate the actual voltage based on the resolution of the DAC and*
 *  output the voltage to the desired DAC channel.                          *
 ****************************************************************************/
#include <stdio.h>
#include <dos.h>
#include <conio.h>

/* Global card base address */
unsigned base;

/****************************************************************************
 *  FUNCTION: write_DAC() - local routine                                   *
 *  PURPOSE: Prompts the user for DAC number and voltage, then calculates  *
 *            the actual output voltage based on resolution, displays it    *
 *            and writes the value to the DAC.                              *
 ****************************************************************************/
void write_DAC(void)
{
float           volt_value_entered,volt_value_expected;
unsigned        counts_entered,dac_number;

/* prompt for the DAC number and desire voltage. */
printf("Enter the DAC number (0 through 15 only): ");
scanf("%u",&dac_number);
printf("\n\nEnter a voltage between 0.000v to 9.997v: ");
scanf("%f",&volt_value_entered);

/* convert entered voltage to associated number of DAC counts. Scale
   factor for 12 bit resolution of DA12-16 is 0.002442. */
volt_value_entered /= 0.002442;

/* compute the digital output needed for this value and the actual voltage
   that will be expected, and display the voltage. */

counts_entered=(int) volt_value_entered;
volt_value_expected = (float) counts_entered * 0.002442;
printf("\nDue to the 12-bit resolution of the DAC, you should expect\n");
printf("to see a voltage of %4.3f.",volt_value_expected);

/* write to the DAC */
outport(base+(2 * dac_number),counts_entered); /* write low byte      */

} /* end write_DAC */


/***************************************************************************
 * FUNCTION: AskForBaseAddress                                             *
 * PURPOSE: Prompt user to enter base address for their I/O card.          *
 **************************************************************************/
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: intro                                                         *
 * PURPOSE: Present user with introductory screen. Get base address.       *
 **************************************************************************/
void intro(void)
   {
   clrscr();
   printf(
   "                        C SAMPLE #1: SAMPLE1.C                          \n\n"
   "  This sample will prompt the user for a voltage between 0 and 10 volts,  \n"
   "  then calculate the actual voltage based on the resolution of the DAC and\n"
   "  output the voltage to the desired DAC channel.                        \n\n"
   "  The following setup of the board is expected:                         \n\n"
   "        þ All DAC voltage ranges should be set to 0v-10v unipolar.        \n\n");

   puts("\n");
   puts("Press any key to continue ... ");
   getch();
   clrscr();
   base = AskForBaseAddress(0x350);
   clrscr();
   } /* end of intro */


/****************************************************************************
 *  FUNCTION: main() - local routine                                        *
 ****************************************************************************/
void main()
    {
    int key_entered, Ch;

    intro();

    /* Set all 16 buffers to 0 */
    for (Ch = 0; Ch < 16; Ch++)
	outport(base + (Ch*2), 0x000);

    inportb(base+10);    // set automatic update mode
    inportb(base+15);    // release zero latch

    do
	{
	clrscr();
	write_DAC();
	printf("\n\nWould you like to output another value (Y or N)? ");
	key_entered = getch();
	} while((key_entered != 'N') && (key_entered != 'n'));

    /* Set all 16 buffers to 0 */
    for (Ch = 0; Ch < 16; Ch++)
	outport(base + (Ch*2), 0x000);

    clrscr();
    puts("DA12-16 Sample1 complete.");
    } /* end main */