ad7703_2.c

一个锅炉温度控制程序

/*
 * ad7703_2.c
 *
 * AD7703
 *
 * 
 *
 *						陈真勇(SA01010010)
 *						[e-mail] or
 *						[e-mail]
 *						中国科学技术大学自动化系
 *						2002/7/20
 */
/*
 *
 *
 *	  修改：王占成
 *	  [e-mail]
 *	  2003.4.26
 *	  
 *
*/ 

#include "Xdata.h"
#include "delay.h"
#include "link.h"
#include "watchdog.h"

void selfcal()
{
	/*第一个AD7703*/
	P2 = 0xF8;   /*?????????????自校正的时候CS为什么要高*/
	ADCAL1=1;
	delay10us();	/*保持CAL高至少4个7703时钟周期，大约2微秒，为了准确延时10微秒*/
					
	ADCAL1=0;
	/*第二个AD7703*/
	P2 = 0xF8;
	ADCAL2=1;
	delay10us();
	ADCAL2=0;
}

UINT read_ad_1()
{
	BYTE i=20;	/* 20 bits to be read */
	UINT mask=0x8000;
	UINT result=0;

	do{;}while( ADDRDY1 );

	EA = 0;
	
	P2 = 0xF8;
	P2 = 0xA8;		/*CS下降沿*/

	/*read first 16 bits of total 20 bits*/
	
	do{
		ADSCLK1=1;/* data valid on rising edge */
	
		if(i>4 && ADSDATA1){	/* max delay 75 ns before data valid. first check i>4*/
			result |= mask;
		}
		mask >>= 1;

		ADSCLK1=0;/* data changed on falling_edge */
	}while(--i);

	P2 = 0xF8;
	EA = 1;

	return result;

}

UINT read_ad_2()
{
	BYTE i=20;	/* 20 bits to be read */
	UINT mask=0x8000;
	UINT result=0;

	do{;}while( ADDRDY2 );

	EA = 0;
	
	P2 = 0xF8;
	P2 = 0x88;		/*CS下降沿*/

	/*read first 16 bits of total 20 bits*/
	
	do{
		ADSCLK2=1;/* data valid on rising edge */
	
		if(i>4 && ADSDATA2){	/* max delay 75 ns before data valid. first check i>4*/
			result |= mask;
		}
		mask >>= 1;

		ADSCLK2=0;/* data changed on falling_edge */
	}while(--i);

	P2 = 0xF8;
	EA = 1;

	return result;
}

void init_ad7703()
{
	BYTE i;
	selfcal();/*self calibration*/
	
	/*将CAL置高后等待3145655个7703时钟周期，大约是1.5秒.完成初始化*/

	for(i=0;i<20;i++){
		clear_watchdog();  /*定期清除看门狗*/
		delay(100);			
	}
}