ADC interfacing with Microcontrollers: Programming for ADC0804
►Programming AVR Microcontroller ►AVR Assembly Programming for ADC0804CODE:
.include "8515def.inc"
.equ rd = PORTB0 ;Read signal PortB.0
.equ wr = PORTB1 ;Write Signal PortB.1
.equ cs = PORTB2 ;Chip Select PortB.2
.equ intr = PORTB3 ;INTR signal PortB.3
.equ adc_port = PINA ;ADC data pins PortA
.def adc_val = r16 ;To store ADC value
.def temp = r17 ;Temporary register
.org 0x00
start:
ldi temp,low(RAMEND) ;Load stack with
out SPL,temp ;RAMEND - highest value
ldi temp,high(RAMEND) ;of internal SRAM
out SPH,temp
sbi DDRB,rd ;Make RD as o/p
sbi DDRB,wr ;Make WR as o/p
sbi DDRB,cs ;Make CS as o/p
again:
rcall conv ;Start ADC Conversion
rcall read ;Read ADC conversion
ldi temp,0xFF
out DDRC,temp ;Make PORTC as o/p Port
out PORTC,adc_val ;Move the read value to PORT C
rjmp again ;Do it again
conv: ;Start conversion
cbi PORTB,cs ;Make CS low
cbi PORTB,wr ;Make WR low
nop
sbi PORTB,wr ;Make WR high
sbi PORTB,cs ;Make CS high
wait:
sbic PINB,intr ;Wait for INTR signal
rjmp wait
ret ;Conversion done
read: ;Read ADC
cbi PORTB,cs ;Make CS low
cbi PORTB,rd ;Make RD low
in adc_val,adc_port ;Read ADC data
sbi PORTB,rd ;Make RD high
sbi PORTB,cs ;Make CS high
ret ;Reading done
CODE:
#include <avr/io.h>#define adc_port PINA //ADC data pins PORTA
#define rd PB0 //Read signal PORTB0
#define wr PB1 //Write signal PORTB1
#define cs PB2 //Chip Select PORTB2
#define intr PB3 //INTR signal PORTB3
void conv(); //Start Conversion
void read(); //Read ADC value
unsigned char adc_val;
int main(){
DDRB = (1<<rd)|(1<<wr)|(1<<cs); //RD, WR, CS as output
DDRC = 0xFF; //PORTC as output
PORTC = 0xFF;
while(1){ //Forever loop
conv(); //Start of conversion
read(); //Read converted ADC
PORTC = adc_val; //Move it to PORTC
}
return 0;
}
void conv(){
PORTB = PORTB & (~((1<<cs)|(1<<wr))); //Make CS and WR low
PORTB = PORTB | ((1<<cs)|(1<<wr)); //Make CS and WR high
while(PINB&(1<<intr)); //Wait for INTR signal
}
void read(){
PORTB = PORTB & ( ~((1<<cs)|(1<<rd))); //Make RD and CS low
adc_val = adc_port; //Read ADC port
PORTB = PORTB | ((1<<cs)|(1<<rd)); //Make RD and CS high
}
The next section of the tutorial will cover the programming of 8051 for ADC0804.
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