/*  DA.C
 *
 *  Analog Output Routines for the SBC1190 with 4 Channel D/A option
 *
 *  This example outputs values from 0 to FFFh to all four channels
 *  of the DAC.
 *
 *  8/3/98
 */

#include <conio.h>
#include <dos.h>

#define PCB          0x0FF00        /*  default base address after reset */
#define P1DIR        PCB+0x050
#define P1CON        PCB+0x054
#define P1LTCH       PCB+0x056
#define P2DIR        PCB+0x058
#define P2CON        PCB+0x05C
#define P2LTCH       PCB+0x05E


#define RTCDTA1      0x80
#define RTCDTA0      (RTCDTA1 ^ 0xFF)

#define RTCCLK1      0x40
#define RTCCLK0      (RTCCLK1 ^ 0xFF)

#define RTCRST1      0x80
#define RTCRST0      (RTCRST1 ^ 0xFF)

#define DACCS1       0x4
#define DACCS0       (DACCS1 ^ 0xFF)

#define LOADREG      0x3000


/*-----------------------------------------------------------------------*
 *  SendDacWord(unsigned dacwd)                                          *
 *                                                                       *
 *   This procedure sends a 16-bit word to the serial DAC.               *
 *   It is assumed that SCLK is low and /DACCS                           *
 *   is low upon entry to this routine.  The data is sent starting with  *
 *   bit 15.                                                             *
 *  Return value : none                                                  *
 *-----------------------------------------------------------------------*/

void SendDacWord(unsigned dacwd)
{
	register int n, p2dta;

	p2dta = inp(P2LTCH);

	for(n=15; n>=0; n--)
	{
		if(dacwd&(1<<n))
		{
			/* send a data bit of 1 */
			outp(P2LTCH, p2dta | RTCDTA1);

			/* set the serial clock line high */
			outp(P2LTCH, (p2dta | RTCDTA1) | RTCCLK1);

			/* set the serial clock line low */
			outp(P2LTCH, (p2dta | RTCDTA1) & RTCCLK0);
		}
		else
		{
			/* send a data bit of 0 */
			outp(P2LTCH, p2dta & RTCDTA0);

			/* set the serial clock line high */
			outp(P2LTCH, (p2dta & RTCDTA0) | RTCCLK1);

			/* set the serial clock line low */
			outp(P2LTCH, (p2dta & RTCDTA0) & RTCCLK0);
		}


	}
}



/*-----------------------------------------------------------------------*
 *  SetupDAC()                                                           *
 *                                                                       *
 *   This procedure sets up the RTCCLK, RTCIO, DACCS and RTCRST lines    *
 *   as outputs. It also clears the RTCCLK line, sets the /RTCRST line   *
 *   low, and sets the /DACCS line low.                                  *
 *  Return value : none                                                  *
 *-----------------------------------------------------------------------*/
void SetupDAC()
{
	/* set P2.7, P2.6 for output */
	outp(P2DIR, 0x3F);

	/* use P2.7, P2.6, P2.5, P2.2 as port pins */
	outp(P2CON, inp(P2CON) & 0x1B);

	/* use P1.2 as port pin */
	outp(P1CON, inp(P1CON) & 0xFB);

	/* set P1.7 (/RTCRST0) and P1.2 (-DACCS) for output */
	outp(P1DIR, inp(P1DIR) & 0x7B);

	/* clear the serial clock */
	outp(P2LTCH, inp(P2LTCH) & RTCCLK0);

	/* set the /DACCS line to 1 */
	outp(P1LTCH, inp(P1LTCH) | DACCS1);

	/* clear the /DACCS line to 0 */
	outp(P1LTCH, inp(P1LTCH) & DACCS0);
}



/*-----------------------------------------------------------------------*
 *  SetDac(int chan, int dacval)                                         *
 *                                                                       *
 *   This routine outputs a voltage on the specified analog channel.     *
 *   No error checking is done on the parameters.                        *
 *                                                                       *
 *  Return value : none                                                  *
 *-----------------------------------------------------------------------*/
void SetDac(int chan, int dacval)
{
	SetupDAC();

	SendDacWord((chan<<14) + LOADREG + dacval);

	outp(P1LTCH, inp(P1LTCH) | DACCS1);     /* set /DACCS high */
}


void main(void)
{
	unsigned n;


	for(;;)
	{
		/* output all values from 0 to 0xFFF */
		for(n=0;n<0x1000;n++)
		{
			SetDac(0, n);   /* channel 0 */
			SetDac(1, n);   /* channel 1 */
			SetDac(2, n);   /* channel 2 */
			SetDac(3, n);   /* channel 3 */
		}
	}
}