Im using external VREF.  

VREF = 2V.

input to ADC is given directly by trimpot which vary from 0V to 2V.

is there any problem in hardware or in initialization of ADC or any noise???

#include<c8051f410.h>
#include "stdio.h"
#include<math.h>
#define SYSCLK 12250000
//
//sfr16 TMR2RL = 0xCA;                   // Timer2 reload value
//sfr16 TMR2 = 0xCC;                     // Timer2 counter
sfr16 adc0 = 0xBD; 

void oscillator_init(void);
void timer2_init(void);
void delay(void);
void lcmnd(unsigned int value);
void ldata(unsigned int value);
void lcd_init(void);
void adc_init(void);

sbit rs=P1^3;
sbit en=P1^4;
sbit rw=P1^5;

unsigned int temp;
int i;		

void delay()
{
unsigned int j;
for(j=0;j<50000;j++);
}

void cmnd(unsigned int value)
{
P2=value;
rs=0;
rw=0;
en=1;
delay();
en=0;
}				    
void ldata(unsigned int value)
{
P2=value;
rs=1;
en=1;
rw=0;
en=1;
delay();
en=0;
}
void lcd_init()
{
cmnd(0x38);
cmnd(0x0C);
cmnd(0x01);
cmnd(0x80);
}


void oscillator_init()
{
OSCICN = 0x86;		//sys clk divided by 2
CLKSEL = 0X00;
XBR0 = 0x00;             //Enable crossbar and weak pullups        
XBR1 = 0x40;
PCA0MD &= ~0x40;

P1MDIN &= 0x7F;			  //0111 1011	 P1.7, P1.2
P1SKIP |= 0x80;			  //1000 0100

}
void main(void)
{
oscillator_init();
lcd_init();
adc_init();
EA=1;
timer2_init();

while(1)
{
cmnd(0x80);
cmnd(0x0C);

ldata((temp/1000)+48);				  // display the result on LCD
ldata(((temp%1000)/100)+48);
ldata(((temp%100)/10)+48);
ldata(((temp%10))+48);
}
}

void adc_read() interrupt 5
{

TF2H = 0; 								   
//AD0BUSY=1;							  //start conv.
// 	
//while (AD0INT == 0);	  			 //conv. in progress

if(AD0INT == 1)	  			 //conv finished
{
ADC0H &= 0x0F;
temp =	ADC0H;			   //adc high byte
temp<<=8;
temp|=ADC0L;	
AD0INT = 0;
}
}
void timer2_init(void)
{
TMR2CN = 0x00;                      // Stop Timer2; Clear TF2;
// use SYSCLK as timebase, 16-bit
// auto-reload
CKCON |= 0x10;                      // Select SYSCLK for timer 2 source
TMR2RL = 65535 - (SYSCLK / 10000);  // Init reload value for 10 us
TMR2 = 0xffff;                      // Set to reload immediately
ET2 = 1;                            // Enable Timer2 interrupts
TR2 = 1;                            // Start Timer2
}
/*
void display() interrupt 10
{
cmnd(0x80);
cmnd(0x0C);

ldata((temp/1000)+48);				  // display the result on LCD
ldata(((temp%1000)/100)+48);
ldata(((temp%100)/10)+48);
ldata(((temp%10))+48);

} */



void adc_init (void)
{

ADC0CN = 0x03;                      // ADC0 disabled, burst-mode disabled,
// conversion triggered on TMR2 overflow

ADC0TK = 0x08;                      // Pre-tracking mode enabled, keep
// default timing settings

REF0CN = 0x02;                      // external VREF  on VREF pin,
// Bias Generator enabled

ADC0MX = 0x0f;      			 // ADC0 positive input = P1.7

ADC0CF = 0x00;                      // Repeat count = 1

ADC0CF |= ((SYSCLK/3000000)-1)<<3;  // Set SAR clock to 3MHz

//EIE1 |= 0x08;                       // Enable ADC0 EOC interrupt

AD0EN = 1;                          // Enable ADC0				
} 

my readings are 

when it have to be 0000, it is 0391

when it have to be 1269, it is  1824

when it have to be 1719, it is  2130

when it have to be 2600, it is  3232

and so on.. 

is there any problem in programming adc or is it because of noise.. ???

I checked 0v. it is OK.. 

Hello expertrs,

im working on c8051f410. adc is working properly. It is showing count 0391 instead of 0000. I think there is issue of noise. can anyone tell how this noise can be removed. Is it removed by hardware or software.

i am using trimpot to vary the input volt to adc. 

 many thanks.

yes i start every line of code with first coloumn. does it make any difference???

im starting the programs with includes. but not mentioned it here. 

sysclk is 24.5 Mhz. 

Timer is for 10 us

when i use the following code i get 0000 at 0V but for 0.04V im getting 0003. but 0002 is not obtained. next im getting 0007, it is skipping the values in between. after 0007, it jumps to 0015, then 0031, then 0063, then 0127, then 0255, 0511,1023,2048. after 2048 it is continuously increasing... Vref=2v, 

 i have changed sysclk and SARCLK..  what else modifications are required???

#define SYSCLK 24500000

void timer2_init(void)
{
TMR2CN = 0x00;                      // Stop Timer2; Clear TF2;
									// use SYSCLK as timebase, 16-bit
									// auto-reload
CKCON |= 0x10;                      // Select SYSCLK for timer 2 source
TMR2RL = - (SYSCLK);  			// Init reload value for 10 us
//TMR2RL = 0xCA;
TMR2 = 0xffff;                      // Set to reload immediately
ET2 = 1;                            // Enable Timer2 interrupts                            // Start Timer2
}

void oscillator_init()
{
OSCICN = 0x87;		//sys clk divided by 1
}



void adc_init (void)
{

ADC0CN = 0x03;                      // ADC0 disabled, burst-mode disabled,
									// conversion triggered on TMR2 overflow

ADC0TK = 0x08;                      // Pre-tracking mode enabled, keep
									// default timing settings

REF0CN = 0x02;                      // external VREF  on VREF pin,
									// Bias Generator enabled

ADC0MX = 0x0F;      			 	// ADC0 positive input = P1.7

ADC0CF = 0x00;                      // Repeat count = 1

ADC0CF |= ((SYSCLK/3000000)-1)<<3;   // Set SAR clock to 3MHz

//EIE1 |= 0x08;                       // Enable ADC0 EOC interrupt

AD0EN = 1;                          // Enable ADC0				
} 


void adc_read() interrupt 5
{
TF2H=0;

//while (AD0INT == 0);	  			//conv. in progress

if(AD0INT == 1)	  			 	//conv finished
{
 //	AD0INT=0;							 // clear ADC conversion complete
 	accumulator+=adc0;
	i++;
	if(i==16)
	{
	i=0;

	accumulator=accumulator/16;
	display();
	accumulator=0;
	}
}
}

void main(void)
{
oscillator_init();
lcd_init();
adc_init();
timer2_init();
EA=1;
while(1)
{
TR2=1;
}
}

sorry..   please help me out

#include<c8051f410.h>
#include "stdio.h"
#include<math.h>
#define SYSCLK 12250000
//
//sfr16 TMR2RL = 0xCA;                   // Timer2 reload value
//sfr16 TMR2 = 0xCC;                     // Timer2 counter
sfr16 adc0 = 0xBD; 

void oscillator_init(void);
void timer2_init(void);
void delay(void);
void lcmnd(unsigned int value);
void ldata(unsigned int value);
void lcd_init(void);
void adc_init(void);

sbit rs=P1^3;
sbit en=P1^4;
sbit rw=P1^5;

unsigned int temp;
int i;		

void delay()
{
unsigned int j;
for(j=0;j<50000;j++);
}

void cmnd(unsigned int value)
{
P2=value;
rs=0;
rw=0;
en=1;
delay();
en=0;
}				    
void ldata(unsigned int value)
{
P2=value;
rs=1;
en=1;
rw=0;
en=1;
delay();
en=0;
}
void lcd_init()
{
cmnd(0x38);
cmnd(0x0C);
cmnd(0x01);
cmnd(0x80);
}


void oscillator_init()
{
OSCICN = 0x86;		//sys clk divided by 2
CLKSEL = 0X00;
XBR0 = 0x00;             //Enable crossbar and weak pullups        
XBR1 = 0x40;
PCA0MD &= ~0x40;

P1MDIN &= 0x7B;			  //0111 1011	 P1.7, P1.2
P1SKIP |= 0x84;			  //1000 0100

}
void main(void)
{
oscillator_init();
lcd_init();
adc_init();
EA=1;
timer2_init();

while(1)
{
cmnd(0x80);
cmnd(0x0C);

ldata((temp/1000)+48);				  // display the result on LCD
ldata(((temp%1000)/100)+48);
ldata(((temp%100)/10)+48);
ldata(((temp%10))+48);
}
}

void adc_read() interrupt 5
{

TF2H = 0; 								   
//AD0BUSY=1;							  //start conv.
// 	
//while (AD0INT == 0);	  			 //conv. in progress

if(AD0INT == 1)	  			 //conv finished
{
ADC0H &= 0x0F;
temp =	ADC0H;			   //adc high byte
temp<<=8;
temp|=ADC0L;	
AD0INT = 0;
}
}
void timer2_init(void)
{
TMR2CN = 0x00;                      // Stop Timer2; Clear TF2;
// use SYSCLK as timebase, 16-bit
// auto-reload
CKCON |= 0x10;                      // Select SYSCLK for timer 2 source
TMR2RL = 65535 - (SYSCLK / 10000);  // Init reload value for 10 us
TMR2 = 0xffff;                      // Set to reload immediately
ET2 = 1;                            // Enable Timer2 interrupts
TR2 = 1;                            // Start Timer2
}
/*
void display() interrupt 10
{
cmnd(0x80);
cmnd(0x0C);

ldata((temp/1000)+48);				  // display the result on LCD
ldata(((temp%1000)/100)+48);
ldata(((temp%100)/10)+48);
ldata(((temp%10))+48);

} */



void adc_init (void)
{

ADC0CN = 0x03;                      // ADC0 disabled, burst-mode disabled,
// conversion triggered on TMR2 overflow

ADC0TK = 0x08;                      // Pre-tracking mode enabled, keep
// default timing settings

REF0CN = 0x02;                      // external VREF  on VREF pin,
// Bias Generator enabled

ADC0MX = 0x0f;      			 // ADC0 positive input = P1.7

ADC0CF = 0x00;                      // Repeat count = 1

ADC0CF |= ((SYSCLK/3000000)-1)<<3;  // Set SAR clock to 3MHz

//EIE1 |= 0x08;                       // Enable ADC0 EOC interrupt

AD0EN = 1;                          // Enable ADC0				
} 

#include<c8051f410.h>
#include "stdio.h"
#include<math.h>
#define SYSCLK 12250000
//
//sfr16 TMR2RL = 0xCA;                   // Timer2 reload value
//sfr16 TMR2 = 0xCC;                     // Timer2 counter
sfr16 adc0 = 0xBD; 

void oscillator_init(void);
void timer2_init(void);
void delay(void);
void lcmnd(unsigned int value);
void ldata(unsigned int value);
void lcd_init(void);
void adc_init(void);

sbit rs=P1^3;
sbit en=P1^4;
sbit rw=P1^5;

unsigned int temp;
int i;		

void delay()
{
unsigned int j;
for(j=0;j<50000;j++);
}

void cmnd(unsigned int value)
{
P2=value;
rs=0;
rw=0;
en=1;
delay();
en=0;
}				    
void ldata(unsigned int value)
{
P2=value;
rs=1;
en=1;
rw=0;
en=1;
delay();
en=0;
}
void lcd_init()
{
cmnd(0x38);
cmnd(0x0C);
cmnd(0x01);
cmnd(0x80);
}


void oscillator_init()
{
OSCICN = 0x86;		//sys clk divided by 2
CLKSEL = 0X00;
XBR0 = 0x00;             //Enable crossbar and weak pullups        
XBR1 = 0x40;
PCA0MD &= ~0x40;

P1MDIN &= 0x7F;			  //0111 1011	 P1.7, P1.2
P1SKIP |= 0x80;			  //1000 0100

}
void main(void)
{
oscillator_init();
lcd_init();
adc_init();
EA=1;
timer2_init();

while(1)
{
cmnd(0x80);
cmnd(0x0C);

ldata((temp/1000)+48);				  // display the result on LCD
ldata(((temp%1000)/100)+48);
ldata(((temp%100)/10)+48);
ldata(((temp%10))+48);
}
}

void adc_read() interrupt 5
{

TF2H = 0; 								   
//AD0BUSY=1;							  //start conv.
// 	
//while (AD0INT == 0);	  			 //conv. in progress

if(AD0INT == 1)	  			 //conv finished
{
ADC0H &= 0x0F;
temp =	ADC0H;			   //adc high byte
temp<<=8;
temp|=ADC0L;	
AD0INT = 0;
}
}
void timer2_init(void)
{
TMR2CN = 0x00;                      // Stop Timer2; Clear TF2;
// use SYSCLK as timebase, 16-bit
// auto-reload
CKCON |= 0x10;                      // Select SYSCLK for timer 2 source
TMR2RL = 65535 - (SYSCLK / 10000);  // Init reload value for 10 us
TMR2 = 0xffff;                      // Set to reload immediately
ET2 = 1;                            // Enable Timer2 interrupts
TR2 = 1;                            // Start Timer2
}
/*
void display() interrupt 10
{
cmnd(0x80);
cmnd(0x0C);

ldata((temp/1000)+48);				  // display the result on LCD
ldata(((temp%1000)/100)+48);
ldata(((temp%100)/10)+48);
ldata(((temp%10))+48);

} */



void adc_init (void)
{

ADC0CN = 0x03;                      // ADC0 disabled, burst-mode disabled,
// conversion triggered on TMR2 overflow

ADC0TK = 0x08;                      // Pre-tracking mode enabled, keep
// default timing settings

REF0CN = 0x02;                      // external VREF  on VREF pin,
// Bias Generator enabled

ADC0MX = 0x0f;      			 // ADC0 positive input = P1.7

ADC0CF = 0x00;                      // Repeat count = 1

ADC0CF |= ((SYSCLK/3000000)-1)<<3;  // Set SAR clock to 3MHz

//EIE1 |= 0x08;                       // Enable ADC0 EOC interrupt

AD0EN = 1;                          // Enable ADC0				
} 

Hello experts,

i m working on C8051f410.. I am new on this device so facing some problems.  I have to enabe internal ADC and display the result(count 0000-4095) on LCD..

I am configuring it in following way. but the counts are not continuous from 0000 to 4095(0000 - 0FFF). 

at 0V it is displaying 0063. at 0.57 it is 0127. But the counts between 0067 and 0127 are not displayed. similar situation is there for other values of voltage. input is given at P1.7.