ad_convert_interrupt.c

PIC单片机的应用

//========================================================
//	A/D conversion and Display 
//
//  使用中断方式处理A/D转换结果 
//
//  Device PIC16F877 
//	set RA2 to an input analog channel, 
//	use RB0, RB1, RB2 and RB3 as I/O output pins select the led of 7-segment_led
//  use PORTD as I/O output port to output the 7-seg value 
//	the 7_seg part is common cathode part
//				2007.5.29
//
//  To do an A/D Conversion, follow these steps:
//  1.  Configure the A/D module:
//      Configure analog pins/voltage reference and digital I/O (ADCON1)
//      Select A/D input channel (ADCON0)
//      Select A/D conversion clock (ADCON0)
//      Turn on A/D module (ADCON0)
//  2. Configure A/D interrupt (if desired):
//      Clear ADIF bit
//      Set ADIE bit
//      Set PEIE bit
///     Set GIE bit
//  3. Wait the required acquisition time.
//  4. Start conversion:
//      Set GO/DONE bit (ADCON0)
//  5. Wait for A/D conversion to complete by either:
//      Polling for the GO/DONE bit to be cleared (interrupts disabled); OR
//      Waiting for the A/D interrupt
//  6. Read A/D Result register pair (ADRESH:ADRESL), 
//      clear bit ADIF if required.
//  7. For the next conversion, go to step 1 or step 2 as required. The A/D conversion time per bit is
//    defined as TAD.
//========================================================

#include<pic.h>
		
const int Dis_table[20]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,
0x77,0x7c,0x39,0x4e,0x79,0x71,0x80,0x40,0x76,0x00};

// save A/D conversion result
volatile static union AD_Res{
	unsigned int	AD_Value;
	unsigned char	AD_Tab[2];
} AD_Result;

// the three BCD code to display
volatile unsigned char num1,num2,num3;

// subroutines
void Delay10ms(void);
void interrupt AD_Process(void);

//=====================================================================
// the main program
void main(void)
{
	// initialize the A/D module
	ADCON0 = 0x51;  //选择A/D通道为RA2,使AD 转换时钟为8tosc,打开A/D 转换器					
	ADCON1 = 0X81;  //转换结果右移,及ADRESH寄存器的高6位为"0"
					//且把RA2口设置为模拟量输入方式
					//RA3接+5V参考电平					
	TRISA2=1; 		//设置RA2为输入方式

	TRISB=0X00;		//initialize the PORTD, set it to a output port
	TRISD=0X00;		//initialize the PORTD, set it to a output port

	PORTB=0xff;		//set RC0-RC3 to high level to disable the 7_seg_led
	

	ADIF=0;         //Clear A/D conversion complete flag bit
	
	PEIE=1;         //Enable the general perehperal interrupt
	ADIE=1;			//Enable A/D interrupt
	GIE=1;          //Enable the general interrupt	
	
	Delay10ms();    //waite the required acquisition time
	
	ADGO=1;			//start the A/D conversion
	
	while(1)
	{
		//For the 7Seg_MPX4_CC part from the Proteus, must set the code for 7_seg_led display first,
		//set the pin to low level to select the corresponding led to work 
		PORTD=Dis_table[num1];			//send the 7_seg code to PORTD
		RB3=0;							//set the corresponding led to work
		Delay10ms();
		RB3=1;
					
		PORTD=Dis_table[num2];	
		RB2=0;
		Delay10ms();
		RB2=1;
		
		PORTD=Dis_table[num3];	
		RB1=0;
		Delay10ms();
		RB1=1;
		
		ADGO=1;
		
		CLRWDT();
	}		
}
// end of the main program
//=====================================================================

//===========================interrupt AD_Process======================
void interrupt AD_Process(void)
{
    if (!(ADIE && ADIF)) return;
    
    CLRWDT();
    
    ADIF=0;
    
    AD_Result.AD_Tab[0]=ADRESL;
    AD_Result.AD_Tab[1]=ADRESH;
    
    AD_Result.AD_Value=(unsigned int)((float)AD_Result.AD_Value/3.3);
    num1=(AD_Result.AD_Value%10);
    num2=((AD_Result.AD_Value-num1)%100)/10;
    num3=(AD_Result.AD_Value-num1-num2*10)/100;    
}
//======================End if interrupt AD_Process=====================

//========================Delay10ms====================================
void Delay10ms(void)
{
	unsigned int i;
	for (i = 2000 ; i>0 ; --i);			
}