09 Experiment

Automatic Porch Light

Source and description

http://sincgrid.in/avr-tutorials/avr-tutorial-experiment-9/

http://sincgrid.in/avr-tutorials/avr-tutorial-experiment-9/

/*Connections:
 *D10(PB2)-red led
 *D11(PB3)-green led
 *D12(PB4)-blue led
 *LDR – A0
 */

#include <avr/io.h>

uint16_t adc_value;            //Variable used to store the value read from the ADC
uint8_t i=0;                    //Variable for the for() loop

void adc_init(void);         //Function to initialize/configure the ADC
uint16_t read_adc(uint8_t channel);    //Function to read an arbitrary analogic channel/pin

int main(void){

DDRB|= _BV(DDB2);        //D10(PB2) as red led
DDRB|= _BV(DDB3);        //D11(PB3) as green led
DDRB|= _BV(DDB4);        //D12(PB4) as blue led

adc_init();        //Setup the ADC

for(;;){        //Our infinite loop
 for(i=0; i<1; i++){

 adc_value = read_adc(i);        //Read one ADC channel

if((adc_value<15)&&(adc_value>0))
{
PORTB|= _BV(PORTB2);
PORTB&= _BV(PORTB3);
PORTB&= _BV(PORTB4);
}
if((adc_value>15)&&(adc_value<75))
{
PORTB&= _BV(PORTB4);
PORTB&= _BV(PORTB2);
PORTB|= _BV(PORTB3);
}

if(adc_value>75)
{
PORTB|= _BV(PORTB4);
PORTB&= _BV(PORTB2);
PORTB&= _BV(PORTB3);
}
}
}

return 0;
}

void adc_init(void){
 ADCSRA |= ((1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0));    //16Mhz/128 = 125Khz the ADC reference clock
 ADMUX |= (1<<REFS0);                //Voltage reference from Avcc (5v)
 ADCSRA |= (1<<ADEN);                //Turn on ADC
 ADCSRA |= (1<<ADSC);                //Do an initial conversion because this one is the slowest
                                              //and to ensure that everything is up and running
}

uint16_t read_adc(uint8_t channel){
 ADMUX &= 0xF0;                    //Clear the older channel that was read
 ADMUX |= channel;                //Defines the new ADC channel to be read
 ADCSRA |= (1<<ADSC);                //Starts a new conversion
 while(ADCSRA & (1<<ADSC));            //Wait until the conversion is done
 return ADCW;                    //Returns the ADC value of the chosen channel
}