pic_hi-tech_c_ad7390_routines.c

PIC_Hi-Tech_C_AD7390_d2a源码

/*

Freely distributable in this original form.
(c) Feb 2000 Shane Tolmie
(c) Working Technologies, producers of the KeyGhost - record keystrokes on PC with tiny device
Any questions or comments?  [e-mail] 
Updates to FAQ available from http://www.keyghost.com/htpic

Analog Devices AD7390 micropower 12-bit DAC for Hi-Tech C v7.85 routines for generic 
PIC micro.

Routines to use DAC (digital to analogue converter, creates an analogue voltage 
from a digital bit stream) 

For Hi-Tech C v7.85, on a generic PIC micro.  

Tested with PIC16F84, PIC12CE674, and PIC16F876 @ 4Mhz, should work with 16Mhz

Code status: tested and works beautifully.

Sample C:

dac_setup();										//sets up port directions
dac_set(x);											//sets voltage between 0V and 5V (or Vref),0000 and 4096 (12-bit)

May need delay routines

*/

#include	<pic.h>
		
#define DAC_LD_BAR			RB1				//load strobe.  Transfers shift register to DAC register
#define DAC_LD_BAR_DIR	TRISB1		//  while active low.  Equivalent to CS bar
#define DAC_CLK					RB3				//clock.  Positive, rising edge clocks data into shift register
#define DAC_CLK_DIR			TRISB3
#define DAC_DATA				RB2				//connects to SDI on DAC.  Serial data output.  Data loads
#define DAC_DATA_DIR		TRISB2		//  directly into the shift register of the DAC

void dac_setup(void)
{
	DAC_LD_BAR=0;
	DAC_CLK=0;
	DAC_DATA=0;

	DAC_LD_BAR_DIR=OUTPUT;
	DAC_DATA_DIR=OUTPUT;
	DAC_CLK_DIR=OUTPUT;
}

void dac_set(unsigned int dacval)
{
	unsigned char i;

	DAC_LD_BAR=LOW;
	DelayUs(10);
	DAC_CLK=HIGH;
	DAC_LD_BAR=HIGH;
	DelayUs(3);

	dacval<<=4;												//only need 12 bits, chop off top four

	//clock lowest 12 bits into dac
	for(i=1; i<=12; i++)
	{
		DelayUs(3);
		dacval<<=1;											//assembles to rotate left into carry
		DAC_DATA=CARRY;									//data clocked in msb first to lsb last
		DAC_CLK=LOW; 										//pulse the clock, data read in on rising edge
		DelayUs(3);
		DAC_CLK=HIGH;
	}
	DelayUs(3);
	DAC_LD_BAR=LOW;										//latch serial data into dac
}