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~: Keil interfacing programs for 8051 :~
After going through sample programs in keil now, you should be aware of how to write simple codes in C language for 8051. So now, let us see some more programs in C language for 8051. These programs are interfacing programs means different peripheral devices are connected with 8051 and we have to write the C program to properly interface these devices with it. different devices are push buttons, keypad, LEDs, 7-segment display, LCD, ADC, DAC etc. here I am not giving the schematic diagrams of interfacing but just a short description of hardware connection is given that tells how the device is connected with 8051.
LED Interfacing:
Hardware:- total 32 LEDs are connected one with each i/o line. Anodes of all 32 LEDs are tied to Vcc and cathode is connected with port pin. Here is the program to generate different chasing effects one after another continuously.
#include<reg51.h>
void delay(void);
void delay()
{
int a,b;
for(a=0;a<100;a++)
for(b=0;b<1000;b++);
}
void main()
{
int i, j, k, l;
for(i=0;i<50;i++) // ON-OFF effect
{
P0=0x00;
P1=0x00;
P2=0x00;
P3=0x00
Delay();
P0=0xFF;
P1=0xFF;
P2=0xFF;
P3=0xFF;
Delay();
}
for(j=0;j<50;j++) // alternate blinking effect
{
P0=0x55;
P1=0x55;
P2=0x55;
P3=0x55
Delay();
P0=0xAA;
P1=0xAA;
P2=0xAA;
P3=0xAA;
Delay();
}
for(k=0;k<50;k++) // ON-OFF effect for port lower and upper nibble
{
P0=0xF0;
Delay();
P0=0x0F;
Delay();
P0=0xFF
P1=0xF0;
Delay();
P1=0x0F;
Delay();
P1=0xFF
P2=0xF0;
Delay();
P2=0x0F;
Delay();
P2=0xFF
P3=0xF0;
Delay();
P3=0x0F;
Delay();
P3=0xFF;
}
for(l=0;l<50;l++) // alternate switching of ports one by one
{
P0=0x00
Delay();
P0=0xFF;
P1=0x00;
Delay();
P1=0xFF;
P2=0x00
Delay();
P2=0xFF;
P3=0x00;
Delay();
P3=0xFF;
}
Push button keypad and 7-segment interfacing:
Hardware:-8 push buttons are connected with P2 with one terminal as common ground. A common anode type 7-segment display is connected to P0. the program displays number 1 to 8 on 7-segment depending upon the key is pressed
#include<reg51.h>
void main(void)
{
loop:P2=0xFF; // send all 1's to P1
while(P21==0xFF); // remain within loop till key is not pressed
switch(P1) // when key pressed detect is
{
case 0xFE:
P0=0xF9; // and display digit from 1 to 8
break;
case 0xFD:
P0=0xA4;
break;
case 0xFB:
P0=0xB0;
break;
case 0xF7:
P0=0x99;
break;
case 0xEF:
P0=0x92;
break;
case 0xDF:
P0=0x82;
break;
case 0xBF:
P0=0xF8;
break;
case 0x7F:
P0=0x80;
break;
}
goto loop;
}
LCD interfacing:
Hardware:- normally all types of text LCDs have 8 data pins and 3 control signals. here data pins are connected with P0 and three control pins RS, R/W and EN are connected with P2.7, P2.6 & P2.5 respectively. Its a 16X2 LCD.
#include <reg51.h>
#include <string.h>
sbit rs = P2^7; // declare P2.7 as rs pin
sbit en = P2^5; // declare p2.5 as enable pin
sbit rw = P2^6; // declare p2.6 as read/write pin
sbit b = P0^7; // busy flag
void writecmd(unsigned char a); // function to send command to LCD
void writedat(unsigned char b); // function to send data to LCD
void busy(); // function to check LCD is busy or not
void writestr(unsigned char *s); // function to write string on LCD
void writecmd(unsigned char a)
{
busy(); // check for LCD is busy or not
rs = 0; // clear rs pin for command
rw = 0; // clear rw pin to write
P0 = a; // send command character
en = 1; // strob LCD
en = 0;
}
void writedat(unsigned char b)
{
busy(); // check for LCD is busy or not
rs = 1; // set rs pin for data
rw = 0; // clear rw pin to write
P0 = b; // send data character
en = 1; // strob LCD
en = 0;
}
void busy()
{
en = 0; // disable display
P0 = 0xFF; // configur P0 as input
rs = 0; // clear rs pin for command
rw = 1; // set rw pin to read
while(b==1)
{
en=0; // strob LCD till P0.7 is 1
en=1;
}
en=0;
}
void writestr(unsigned char *s)
{
unsigned char l,i;
l = strlen(s); // get the length of string
for(i=1;i<l;i++)
{
writedat(*s); // write every char one by one
s++;
}
}
main()
{
P0=0x00; // P0 and P0 as output ports
P2=0x00;
writecmd(0x3C); // initialize LCD
writecmd(0x0E);
writecmd(0x01); // clear memory and home cursor
writestr("Wel-Come to LCD"); // write message in first line
writecmd(0xC4); // move cursor to second line 4th pos
writestr("Program");
while(1) // continuous loop
}
ADC interfacing:
Hardware:- here I have interfaced 8 bit ADC 0804 with 8051 and given program displays digital equivalent value (HEX) of any analog input on 2-digit multiplex seven segment. Usually ADC has four control signals. CS (chip select-active low), WR (SOC-start of conversion-active low), RD(OE-o/p enable-active low)and INT. from these four only INT is o/p form ADC all other are inputs. The CS is connected with ground. WR, RD and INT signals are connected with P3.0, P3.1 and P3.2 respectively. 8 data pins are connected with P1. Multiplex 7-segment has 8 data pins and 2 display select pins. data pins are connected with P0 and display select pins are connected to P2.7 and P2.6 respectively.
#include <reg51.h>
#include <string.h>
sbit wr = P3^0; // ADC write enable
sbit rd = P3^1; // ADC read enable
sbit d1 = P2^7 // display 1 select bit
sbit d2 = P2^6 // display 2 select bit
unsigned char data d;
unsigned int a=0,b=0,c=0;
void int1(void) interrupt 1 //external interrupt 1 subroutine
{
EA=0 // first disable any other interrupt
rd = 0; // send read signal
d=P1; // read the data from port
rd=1;
a = (d & 0x0F); // saperate upper and lower
b = d >> 4; // nibbles
EA=1; // again enable interrupts
}
void tmr1(void) interrupt 3 // timer 1 overflow interrupt
{
c++; // count no of timer 1 interrupts
TH1=0xEC; // reload timer
TL1=0x77;
TF1=0; // clear timer 1 overflow flag
if((c%2)==0) // check interrupt has arrived even
{ // times or odd times
d1=1; // alternatively change display
d2=0; // for even times
P0=b;
}
else // and odd times
{
d1=0;
d2=1;
P0=a;
}
}
main()
{
P0=0x00; // P0 output ports
P1=0xFF; // P1 input port
TMOD=0x90; // initialize T1 as 16 bit timer
TH1=0xEC; // load count 60535(=EC77h)
TL1=0x77; // so it will overflow after 5 ms
TR1=1; // start timer
d1=0;
d2=1; //enable first display
P0=a; //display 0 initially
IE=0x89; // enable external and timer interrupts
wr = 0; // send write signal
wr = 1;
while(1); // wait in continuous loop
}
DAC interfacing:
Hardware:-a 8 bit DAC is connected to P2. Its two control signals WR and CS are tied to ground. Here I am writing a program to generate three different types of waveforms square, triangular and staircase type. To select desire waveform three push buttons are connected at P3.0 to P3.2.
#include<reg51.h>
void delay1(); //key debounce delay
void delay2(); // delay for frequency
void sqrarwave(); // function to generate square wave
void triwave(); // function to generate triangular wave
void stairwave(); // function to generate staircase wave
void delay1() // approx. 100 ms delay
{
int a,b;
for(a=0;a<100;a++)
for(b=0;b<1000;b++);
}
void delay2() // approx 1 ms delay
{
int c;
for(c=0;c<1000;c++);
}
void squarwave()
{
while(P3==0xFF) // till any button is not pressed
{
P2=0xFF; // first send all high to P2
Delay2();
P2=0x00; // then send all low to P2
Delay2();
}
}
void triwave()
{
unsigned char d;
while(P3==0xFF)
{
for(d=0x00;d<0xFF;d++) // send values 00 to FF
{
P2=d; // one by one for positive ramp
}
for(d=0xFF;d<0x00;d--) // send values FF to 00
{
P2=d; // one by one for negative ramp
}
}
void stairwave()
{
while(P3==0xFF)
{
P2=0x00; // step by step increment
Delay2();
P2=0x20; // values sent to P2
Delay2();
P2=0x40;
Delay2();
P2=0x80;
Delay2();
}
}
void main()
{
P2=0x00; // P2 as output port
P3=0xFF; // P3 as input port
While(P3=0xFF); // wait till any button is pressed
Switch(P3)
{
case 0xFE: // for first button
delay1(); // key debounce delay
P3=0xFF; // send all 1’s again to P3
squarwave(); // generate square wave
break;
case 0xFD:
delay1();
P3=0xFF;
triwave();
break;
case 0xFB:
delay1();
P3=0xFF;
stairwave();
break;
}
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