#include<regx51.h>
#define TIMER0_COUNT 0xDC11
#define adc_in P0
sbit rs=P3^5;
sbit rw=P3^4;
sbit en=P3^3;
sbit adc_rd=P2^0;
sbit adc_wr=P2^1;
static unsigned timer0_tick;
const char int2char[]="0123456789";
void delay(void)
{
  unsigned int i,j;
  for(i=0;i<3;i++)
  for(j=0;j<255;j++);
}

void write_command(unsigned command)
{
  rw=0;
  rs=0;
  en=1;
  P1=command;
  en=0;
  rs=1;
  rw=1;
  delay();
}

void write_data(unsigned lcddata)
{
  rw=0;
  rs=1;
  en=1;
  P1=lcddata;
  en=0;
  rs=0;
  rw=1;
  delay();
}

void set_lcd(void)
{
  write_command(56);
  write_command(12);
  write_command(6);
}

void clear_lcd(void)
{
  write_command(1);
  write_command(2);
}

void display_string(char *p)
{
  while(*p)
  {
     write_data(*p);
	 p++;
  }
}

void gotoxy(unsigned x,unsigned y)
{
  if(x==1)
     write_command(128+y);
  else
     write_command(192+y);
}

void display_number(unsigned char number)
{
  unsigned char x,y,i=2;
  int z;
  z=(int) number;
  z=z<<1;
  x=z/10;
  y=z-x*10;
  gotoxy(2,3);
  write_data(int2char[y]);
  z=x;
  x=z/10;
  y=z-x*10;
  gotoxy(2,2);
  write_data(int2char[y]);
  gotoxy(2,1);
  display_string(".");
  z=x;
  x=z/10;
  y=z-x*10;
  gotoxy(2,0);
  write_data(int2char[y]);
  gotoxy(2,4);
  display_string("Volt");
}

static void timer0_isr(void) interrupt 1 using 1
{
  TR0=0;
  TL0=(TIMER0_COUNT & 0X00FF);
  TH0=(TIMER0_COUNT >> 8);
  TR0=1;
  timer0_tick++;
  if(timer0_tick==200){
     adc_wr=0;
	 timer0_tick=0;
	 adc_wr=1;
	}
}

static void int0_isr(void) interrupt 0 using 0
{
  unsigned char voltage;
  adc_in=0xff;
  adc_rd=0;
  voltage=adc_in;
  voltage=voltage<<1;
  adc_rd=1;
  gotoxy(2,0);
  display_number(voltage);
}

static void timer0_initialize(void)
{
  EA=0;
  timer0_tick=0;
  TR0=0;
  TMOD &=0xf0;
  TMOD |=0x01;
  TL0=( TIMER0_COUNT & 0x00FF);
  TH0=( TIMER0_COUNT >> 8);
  PT0=0;
  ET0=1;
  TR0=1;
  EA=1;
}

void main(void){
  set_lcd();
  clear_lcd();
  display_string("Input voltage:");
  timer0_initialize();
  IT0=1;
  EX0=1;
  while(1);
}