[Blue Bridge Road - bug free code] pcf8591 - code analysis of AD conversion

Read Rb2 And display the voltage value on the nixie tube , Range 0.00~5.00V, By changing the sliding rheostat Rb2 The resistance value of can change the voltage value

main.c

#include"stc15f2k60s2.h"
#include"iic.h"
#include"intrins.h"

typedef unsigned char uchar;
typedef unsigned int uint;

uchar dsp_code[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};
uchar dsp_ADC[8]={0xff,0xff,0xff,0xff,0xff,0xff};

uint value;
uchar count_adc;

void Timer_Init()
{
	AUXR|= 0x80;
	TMOD&= 0xf0;
	TL0=0xcd;
	TH0=0xd4;
	TR0=1;
	ET0=1;
	EA=1;
}

void serviceTimer() interrupt 1
{
	static uchar dsp_com=0;

	P0=0;P2=0xc0;P2=0;

	P0=dsp_ADC[dsp_com];P2=0xe0;P2=0;

	P0=1<<dsp_com;P2=0xc0;P2=0;

	if(++dsp_com==8)dsp_com=0;

	++count_adc;
}

void Initsystem()
{
	P0=0xff;P2=0x80;P2=0;
	P0=0x00;P2=0xa0;P2=0;
}

void main()
{
	char i=0;
	Initsystem();
	for(i=0;i<5;i++)
	{
		value=read_adc(0x03)*1.96+0.5;
	}
	Timer_Init();
	while(1)
	{
		if(count_adc>199)
		{
			count_adc=0;
			EA=0;
			value=read_adc(0x03)*1.96+0.5;
			EA=1;
		}
	dsp_ADC[5]=dsp_code[value/100]&0x7f;
	dsp_ADC[6]=dsp_code[value/10%10];
	dsp_ADC[7]=dsp_code[value%10];
	}
}

iic.c

/*
   Program description : IIC Bus driver 
   Software environment : Keil uVision 4.10 
   Hardware environment : CT107 SCM comprehensive training platform  8051,12MHz
   Japan      period : 2011-8-9
*/

#include "reg52.h"
#include "intrins.h"
#define DELAY_TIME 5  


#define SlaveAddrW 0xA0
#define SlaveAddrR 0xA1

// Bus pin definition 
sbit SDA = P2^1;  /*  cable  */
sbit SCL = P2^0;  /*  Clock line  */

void IIC_Delay(unsigned char i)
{
	do
	{
		_nop_();
	}
	while(i--);
}

// Bus start condition 
void IIC_Start(void)
{
	SDA = 1;
	SCL = 1;
	IIC_Delay(DELAY_TIME);
	SDA = 0;
	IIC_Delay(DELAY_TIME);
	SCL = 0;	
}

// Bus stop condition 
void IIC_Stop(void)
{
	SDA = 0;
	SCL = 1;
	IIC_Delay(DELAY_TIME);
	SDA = 1;
	IIC_Delay(DELAY_TIME);
}



// Waiting for an answer 
bit IIC_WaitAck(void)
{
	bit ackbit;
	SCL=1;
	IIC_Delay(DELAY_TIME);
	ackbit=SDA;
	SCL=0;
	IIC_Delay(DELAY_TIME);

	return ackbit;
	
}

// adopt I2C The bus sends data 
void IIC_SendByte(unsigned char byt)
{
	unsigned char i;
	for(i=0;i<8;i++)
	{   
		SCL=0;
		IIC_Delay(DELAY_TIME);
		if(byt&0x80) 
		{	
			SDA = 1;
		}
		else 
		{
			SDA = 0;
		}
		IIC_Delay(DELAY_TIME);
		SCL = 1;
		byt <<= 1;
		IIC_Delay(DELAY_TIME);	
	}
	SCL = 0;
	IIC_WaitAck();
}

// from I2C Data is received on the bus 
unsigned char IIC_RecByte(void)
{
	unsigned char da;
	unsigned char i;
	
	for(i=0;i<8;i++)
	{   
		SCL = 1;
		IIC_Delay(DELAY_TIME);
		da <<= 1;
		if(SDA) 
		da |= 0x01;
		SCL = 0;
		IIC_Delay(DELAY_TIME);
	}
	IIC_WaitAck();
	return da;
}

void IIC_SendAck(bit ackbit)
{
	SCL=0;
	SDA=ackbit;
	IIC_Delay(DELAY_TIME);
	SCL=1;
	IIC_Delay(DELAY_TIME);
	SCL=0;
	IIC_Delay(DELAY_TIME);
	SDA=1;
	IIC_Delay(DELAY_TIME);
}

unsigned char read_adc(unsigned char add)
{
	unsigned char val;

	IIC_Start();
	IIC_SendByte(0x90);
	IIC_SendByte(add);

	IIC_Start();
	IIC_SendByte(0x91);
	val=IIC_RecByte();
	IIC_Stop();

	return val;
}

iic.h

#ifndef _IIC_H
#define _IIC_H

// Function declaration 
void IIC_Start(void); 
void IIC_Stop(void);  
void IIC_SendAck(bit ackbit); 
void IIC_SendByte(unsigned char byt); 
bit IIC_WaitAck(void);  
unsigned char IIC_RecByte(void); 
unsigned char read_adc(unsigned char add);

#endif