/****************************************************************************
 *  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>



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: 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(unsigned int Address)
{
char            ch;
float           volt_value_entered,volt_value_expected;
unsigned        counts_entered,temp,dac_number;
unsigned char   lo_byte,hi_byte;

/* prompt for the DAC number and desire voltage. */

do {
   gotoxy (1,3);
   clreol();
   printf("Enter the DAC number (0 through 5 only): ");
   ch=getche();
   dac_number=ch-'0';         /* using ascii code to get dac_number*/
} while ((dac_number < 0) || (dac_number > 5));
do {
   gotoxy (1,7);
   clreol();
   printf("Enter a voltage between 0.000v to 9.997v: ");
   scanf("%f",&volt_value_entered);
} while ((volt_value_entered<0.000) || (volt_value_entered>9.997));
   volt_value_entered /= 0.002441;

/* 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 * 0.002441;
printf("\n\n\nDue to the 12-bit resolution of the DAC, you should expect\n");
printf("to see a voltage of %4.3f.",volt_value_expected);

/* prepare the control word and write to the DAC */

temp = counts_entered;
counts_entered /= 256;                       /* extract hi byte            */
hi_byte = (unsigned char) counts_entered;    /* convert to character       */
temp %= 256;                                 /* extract low byte           */
lo_byte = (unsigned char) temp;              /* convert to character       */
outportb(Address+(2 * dac_number),lo_byte); /* write low byte         */
outportb(Address+(2*dac_number+1),hi_byte); /* write high byte        */
} /* end write_DAC */

/****************************************************************************
 *  FUNCTION: main() - local routine                                        *
 ****************************************************************************/
void main()
{
int key_entered;
unsigned int Address;

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"
"  Board Configuration:                                                  \n\n"
"      -- The Base Address should be set to the address which will be      \n"
"         entered during program execution.                                \n"
"      -- Reference voltage for the DACs should be -10V.     (required)    \n"
"      -- All remaining jumper settings are irrelevant                   \n\n");

Address=AskForBaseAddress(0x350);

puts("\n\n\n\nPress any key to continue");
getch();
do
   {
   clrscr();
   write_DAC(Address);
   printf("\n\n\nWould you like to output another value (Y or N)? ");
   key_entered = getch();
   }
while((key_entered != 'N') && (key_entered != 'n'));
clrscr();
} /* end main */