Electronics Forum -> Adc0808 Channel Interfarance Problem.

Electronics Forum

Help

Members

Calendar

Welcome Guest ( Log In | Register )

Resend Validation Email

Electronics Forum -> Digital Electronics and Embedded Design -> Embedded Designs

Forum Rules (Please read before posting)

Adc0808 Channel Interfarance Problem., urgent help required

Topic Options

Qaisar Azeemi

Posted: March 24, 2012 02:00 pm

Newbie

Group: Members+
Posts: 46
Member No.: 36,124
Joined: November 17, 2011

hi friends,

i am getting 3 analog signals at the inputs of ADC0808 and i am displaying it on LCD. they are voltage current and temperature signals. the problem is that when i vary one of the analog input it also effects the data from other inputs. that is if i vary voltage it resutls in the variation of voltage data, current data and temprature data on tha Screen of LCD. i tried my best to isolate it from each other by putting delays and clearing the arrays and data memory locations but the problem is as it is... please help me to rectify my problem...

following is my code:

CODE

#include <reg52.h>

#define select P3
#define Port P2 // control port
#define adc_input P1
#define data_port P0 // data from microcontroller to LCD
#define sec 50
#define scan 10

sbit ADC_A=Port^0; //ADC
sbit ADC_B=Port^1; //ADC
sbit RS=Port^7; //LCD
sbit E=Port^5; //LCD
sbit ctl=Port^6; //LCD
sbit SC=Port^4; //ADC
sbit CLK=Port^3; //ADC
sbit ALE=Port^2; //ADC

sbit v28=select^4; // carger 28v selected
sbit v14=select^5;
sbit v7=select^6;
sbit off=select^7;
sbit intr=select^2;
sbit c28=select^0;
sbit c14=select^1;
sbit c7=select^3;

unsigned int test_intermediate3=0, test_final=0, select_mem=0, x=0;
unsigned int test_intermediate1[scan], test_intermediate2[3]={0,0,0};
unsigned char temp[]={"Temp: "}, vna[]={" Volt: Amp: "}, hnm[]={" hr min %"}, bnc[]={"Backup: %Charge"};

//------------------- . --------------------------

void delay(unsigned int msec)
{
int i,j;
for(i=0; i==msec; i++)
for(j=0; j==1275; j++);

}

//...........;;;;;;;;;;..........................

void long_delay(unsigned int second)
{
int i,j;
for (j=0; j<second; j++)
for (i=0; i<0xffff; i++);
}

//---------------- timer 0 interrupt----------------

void timer0() interrupt 1
{

CLK=~CLK; // Toggle port bit p3.5
TR0=0; // stop timer
TH0=0xff; // 500hz clock for adc
TL0=0xff;
TR0=1; // start timer
}

//;;;;;;;;;;;;;;;;;;;;;;;;;;;

void switch2(void)
{
if (v7==1 & v14==0 & v28==0)
{
c7=1; c14=0; c28=0;
}

else
if(v14==1 & v7==0 & v28==0)
{
c14=1; c7=0; c28=0;
}
else
if (v28==1 & v7==0 & v14==0)
{
c28=1; c14=0; c7=0;
}

}

//---------------- External 0 interrupt----------------

void switching() interrupt 0
{

intr=1;
delay(sec*4);
select = select_mem;
intr=1;
delay(sec*4);

// ...............---------........................

if(v28==0 & v14==0 & v7==0 & off==1)
{ off=0; v7=1; v28=0; v14=0; }

else
if(v28==0 & v14==0 & v7==1 & off==0) //e1
{ v7=0; v14=1; v28=0; off=0; }

else
if(v28==0 & v14==1 & v7==0 & off==0) //e2
{ v14=0; v28=1; v7=0; off=0; }

else
if(v28==1 & v14==0 & v7==0 & off==0) //e3
{ v28=0; v14=0; v7=0; off=1; }

delay(sec*4);
intr=1;
c7=0; c14=0; c28=0;
delay(sec*4);
select_mem = select;

long_delay(10);
switch2();

}

//.................. LCD .................

void lcd_cmd( unsigned int item )
{
data_port=item; //command on data port p0 of lcd
RS=0; // selecting command register of lcd
// RW=0;
E=1;
delay(1);
E=0;

}

void lcd_data( unsigned int item )
{
data_port=item; //data on data port p0 of lcd
RS=1; // selecting data register of lcd
// RW=0;
E=1;
delay(1);
E=0;

}

//----------- custom character Generation for Degree symbol-----------

void shape()
{

lcd_cmd(64); // first location in CGRAM
delay(sec);
lcd_data(2);
delay(sec);
lcd_data(5);
delay(sec);
lcd_data(2);
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(0);
delay(sec);

}

//-------------------- for volt symbol-----------------

void shape2()
{

lcd_cmd(72); // second location in CGRAM
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(17);
delay(sec);
lcd_data(17);
delay(sec);
lcd_data(17);
delay(sec);
lcd_data(10);
delay(sec);
lcd_data(4);
delay(sec);
lcd_data(0);
delay(sec);

}

//---------------------- for current symbol-------------------

void shape3()
{

lcd_cmd(80); // Third location in CGRAM
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(0);
delay(sec);
lcd_data(4);
delay(sec);
lcd_data(10);
delay(sec);
lcd_data(17);
delay(sec);
lcd_data(31);
delay(sec);
lcd_data(17);
delay(sec);
lcd_data(0);
delay(sec);

}

//..... Converting binary value of ADC to ASCII value of LCD for Temprature........

void convert()
{
int s;

test_final=(((9*test_intermediate3)/5)+32); // Farenhite conversion

s=test_final/100;
test_final=test_final%100;

lcd_cmd(0xc5);
delay(sec);
if (s!=0)
{
lcd_data(s+48); //c5
delay(sec);
}
else
{
lcd_cmd(0x06);
delay(sec);
}

s=test_final/10;
test_final=test_final%10;

lcd_data(s+48); //c6
delay(sec);
lcd_data(test_final+48); //c7
delay(sec);
lcd_data(0); // space for degree symbol
delay(sec);
lcd_data('F');
delay(sec);
lcd_data(' ');
delay(sec);

//------------------- for Celcius scale----------------

test_final=test_intermediate3;

s=test_final/100;
test_final=test_final%100;

lcd_cmd(0xcB);
delay(sec);
if (s!=0)
{
lcd_data(s+48); // 1st digit MS
delay(sec);
}
else
{
lcd_cmd(0x06);
delay(sec);
}

s=test_final/10; // 2nd digit
test_final=test_final%10; // 3rd digit LS

lcd_data(s+48); //89
delay(sec);
lcd_data(test_final+48); //88
delay(sec);
lcd_data(0); // space for degree symbol
delay(sec);
lcd_data('C');
delay(sec);
lcd_data(' ');
delay(sec);

}

// Converting binary value of ADC to ASCII value of LCD for volts

void Convert2()
{
int s;
//.................... Voltage conversion ............................

test_final=test_intermediate3/5;

s=test_final/100;
test_final=test_final%100;

lcd_cmd(0x85);
delay(sec);
if (s!=0)
{
lcd_data(s+48);
delay(sec);
}
else
{
lcd_cmd(0x06);
delay(sec);
}

s=test_final/10;
test_final=test_final%10;

lcd_data(s+48);
delay(sec);
lcd_data(test_final+48);
delay(sec);
lcd_data(1);
delay(sec);
lcd_data(' ');
delay(sec);
}

//-------------------..................-------------------

void Convert3()
{
int s;
//.................... current conversion ............................

test_final=test_intermediate3;

s=test_final/100;
test_final=test_final%100;

lcd_cmd(0x8D);
delay(sec);
if (s!=0)
{
lcd_data(s+48);
delay(sec);
}
else
{
lcd_cmd(0x06);
delay(sec);
}

s=test_final/10;
test_final=test_final%10;

lcd_data(s+48);
delay(sec);
lcd_data(test_final+48);
delay(sec);
lcd_data(2);
delay(sec);

}

//.........--------.......Main Program.......-------........

void main()
{

int i,j,k,l,m,n;
adc_input=0xff; // making p1 as input port
TMOD=0x01; // timer 0, mode 1
TH0=0xff; // 500hz clock for adc
TL0=0xff;
TR0=1; // timer start

IE=0x83; // interrupt enable; timer interrupt, external interrupt and globle interrupt.

v28=0; v14=0; v7=0; off=1; // intializing charger selection to 0V
c28=0; c14=0; c7=0;
intr=1;

select_mem = select;
delay(sec);

lcd_cmd(0x38); // initializing LCD module
delay(sec);

lcd_cmd(0x0c);
delay(sec);

lcd_cmd(0x01);
delay(sec);

lcd_cmd(0x06);
delay(sec);

//;;;;;;;;;;;;;;-----------;;;;;;;;;;;;;;;
//......... volt and ampere display........

lcd_cmd(0x80);
delay(sec);

for(i=0; vna[i]!='\0'; i++)
{
lcd_data(vna[i]);
delay(sec);
}

//;;;;;;;;;;;;-----------------------;;;;;;;;;;;;;;;;;
//..........- Back up and %Charge display ----........

lcd_cmd(0x90);
delay(sec);

for(i=0; bnc[i]!='\0'; i++)
{
lcd_data(bnc[i]);
delay(sec);
}

//;;;;;;;;;;;;;;-----------;;;;;;;;;;;;;;;
//......... ----Temp: display-----........

lcd_cmd(0xc0);
delay(sec);

for(i=0; temp[i]!='\0'; i++)
{
lcd_data(temp[i]);
delay(sec);
}

//;;;;;;;;;;;;;;-------------------------;;;;;;;;;;;;;;;;;
//.............- hour and minute display ------...........

lcd_cmd(0xD0);
delay(sec);

for(i=0; hnm[i]!='\0'; i++)
{
lcd_data(hnm[i]);
delay(sec);
}

//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

while(1)
{

//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;Temprature samples;;;;;;;;;;;;;;;;;;;;;;

test_intermediate3=0;
test_final=0;
test_intermediate2[0]=0;
test_intermediate2[1]=0;
test_intermediate2[2]=0;

for(j=0;j<3;j++)
{
for(i=0;i<scan;i++)
{ ctl=0;
delay(10);
ADC_A=0;
ADC_B=0; // channel 0 is selected ; pin 26 of ADC

delay(200);

ALE=0;
SC=0;
delay(1);

ALE=1;
delay(1);
SC=1;
delay(1);

ALE=0;
delay(1);
SC=0;

delay(200);

test_intermediate1[i]=adc_input/scan;

}

for(i=0;i<scan;i++)
test_intermediate2[j]+=test_intermediate1[i];
}

test_intermediate2[0]=test_intermediate2[0]/3;
test_intermediate2[1]=test_intermediate2[1]/3;
test_intermediate2[2]=test_intermediate2[2]/3;

test_intermediate3=test_intermediate2[0] + test_intermediate2[1] + test_intermediate2[2];

convert();
shape();

long_delay(1);
ctl=1;
delay(10);
ADC_A=1;
ADC_B=0; // channel 1 is selected for voltage

//;;;;;;;;;;;;;;;;; Voltage samples;;;;;;;;;;;;;;;;;;;;;;;;;

test_intermediate3=0;
test_final=0;
test_intermediate2[0]=0;
test_intermediate2[1]=0;
test_intermediate2[2]=0;

for( k=0;k<3;k++)
{
for(l=0;l<scan;l++)
{
delay(10);
ADC_A=1;
ADC_B=0; // channel 1 is selected

delay(200);

ALE=0;
SC=0;
delay(1);

ALE=1;
delay(1);
SC=1;
delay(1);

ALE=0;
delay(1);
SC=0;

delay(200);

test_intermediate1[l]=adc_input/scan;

}

for(i=0;i<scan;i++)
test_intermediate2[k]+=test_intermediate1[i];
}

test_intermediate2[0]=test_intermediate2[0]/3;
test_intermediate2[1]=test_intermediate2[1]/3;
test_intermediate2[2]=test_intermediate2[2]/3;

test_intermediate3=test_intermediate2[0] + test_intermediate2[1] + test_intermediate2[2];

Convert2();
shape2();

long_delay(1);
ADC_A=0;
ADC_B=1; // channel 2 is selected for current

//;;;;;;;;;;;;;;;;; Current samples;;;;;;;;;;;;;;;;;;;;;;;;;

test_intermediate3=0;
test_final=0;
test_intermediate2[0]=0;
test_intermediate2[1]=0;
test_intermediate2[2]=0;

for( m=0;m<3;m++)
{
for( n=0;n<scan;n++)
{
delay(10);
ADC_A=0;
ADC_B=1; // channel 2 is selected

delay(200);

ALE=0;
SC=0;
delay(1);

ALE=1;
delay(1);
SC=1;
delay(1);

ALE=0;
delay(1);
SC=0;

delay(200);

test_intermediate1[n]=adc_input/scan;

}

for(i=0;i<scan;i++)
test_intermediate2[m]+=test_intermediate1[i];
}

test_intermediate2[0]=test_intermediate2[0]/3;
test_intermediate2[1]=test_intermediate2[1]/3;
test_intermediate2[2]=test_intermediate2[2]/3;

test_intermediate3=test_intermediate2[0] + test_intermediate2[1] + test_intermediate2[2];

Convert3();
shape3();
long_delay(1);

}
}

i dont know how to upload immage here from my pc so plz consider all connections ok. and eoc pin of adc0808 is tied with Vcc.

thanking you in anticipation.

regards
Qaisar azeemi.

Gorgon	Posted: March 25, 2012 02:12 am
Forum Addict ++ Group: Trusted Members Posts: 2,930 Member No.: 3,861 Joined: December 18, 2005	Is the ADCs voltage references connected in any way to the voltage you measure? If your reference is variable all measurements will be variable too. TOK -------------------- Light travels faster than sound. That's why some people appear bright until they speak!

Qaisar Azeemi	Posted: March 26, 2012 06:05 am
Newbie Group: Members+ Posts: 46 Member No.: 36,124 Joined: November 17, 2011	yes refrance is connected. i have connected 2.56v dc to +Vref using a voltage divider network... it is fixed...

Sch3mat1c	Posted: March 26, 2012 06:13 pm
Forum Addict ++ Group: Moderators Posts: 18,193 Member No.: 73 Joined: July 24, 2002	Circuit, layout? -------------------- Answering questions is a tricky subject to practice. Not due to the difficulty of formulating or locating answers, but due to the human inability of asking the right questions; a skill that, were one to possess, would put them in the "answering" category.

Qaisar Azeemi	Posted: March 27, 2012 06:32 am
Newbie Group: Members+ Posts: 46 Member No.: 36,124 Joined: November 17, 2011	how do i post immage ...... i don't know... :-(

MacFromOK	Posted: March 27, 2012 05:10 pm
Forum Addict ++ Group: Spamminator Taskforce Posts: 13,002 Member No.: 5,314 Joined: June 04, 2006	You can't upload images directly, but you can use a free image hosting service (such as photobucket.com) and either use the IMG tags (if the pic isn't too large) or just post a link to the image. -------------------- Mac * "Basic research is what I'm doing when I don't know what I'm doing." [Wernher Von Braun] * is not responsible for errors, consequential damage, or... anything.

CoulombMagician	Posted: April 01, 2012 04:13 pm
Forum Addict Group: Spamminator Taskforce Posts: 977 Member No.: 3,131 Joined: August 29, 2005	Been there, done that. Connect one input to ground and switch the mux to that input before reading any of your other inputs. This will eliminate the crosscoupling between channels in most cases. The "proper" way to do it is to drive each input with an active low impedance source which will discharge the input capacitance of the ADC, most people however just connect passive sources to ADC inputs.

1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)

0 Members:

« Next Oldest | Embedded Designs | Next Newest »

:: support us ::

ElectronicsSkin by DutchDork & The-Force