Question

Using Arduino:

Three analog temperature Sensors are connected to channels 0, 1, and 2 of ATMEG328P. Write an AVR C program that continuously reads the temperature values from the three sensors connected to channels 0, 1 and 2 (ADC0, ADC1, ADC2). The program will turn on an LED connected to PORTD pin 3 if the values of the three sensors are not equal. Use the following ADC configuration.

 Single-ended mode operation

.  Select manual trigger mode.

 Disable ADC interrupt.

 Select AVCC as the reference voltage.

 ADC result is right justified.

 Select the ADC Prescaler 64.

Expert Answer

Answer 1

ANSWER:

GIVEN THAT:

int temp_sensor()
{
ADCSRAbits.ADEN=1; //ADC ENABLE
ADMUXbits.REFS1=0; //AVcc IS REFERENCE
ADMUXbits.REFS0=1;
ADMUXbits.ADLAR=0; //RIGHT JUSTIFIED
ADCSRAbits.ADATE=0; //MANUAL TRIGGER
ADCSRAbits.ADIE=0; //interrupt disabled
ADCSRAbits.ADPS2=1; //PRESCALAR 64
ADCSRAbits.ADPS1=1;
ADCSRAbits.ADPS0=0;

ADMUXbits.MUX0=0; //ADC0 CHANNEL
ADCSRAbits.ADSC=1; //START CONVERSION
#if (ADCSRAbits.ADIF ==1)
PORTB=ADCL; //storing value to port B data register
ADCSRAbits.ADSC=0; //STOP CONVERSION
#endif

ADMUXbits.MUX0=1; //ADC1 CHANNEL
ADCSRAbits.ADSC=1; //START CONVERSION
#if (ADCSRAbits.ADIF ==1)
PORTC=ADCL; //storing value to port C data register
ADCSRAbits.ADSC=0; //STOP CONVERSION
#endif

ADMUXbits.MUX2=1; //ADC2 CHANNEL
ADCSRAbits.ADSC=1; //START CONVERSION
#if (ADCSRAbits.ADIF ==1)
PORTD=ADCL; //storing value to port D data register
ADCSRAbits.ADSC=0; //STOP CONVERSION
#endif

#if(PORTB != PORT C && PORT C != PORT D && PORTD != PORT B)
PINDbits.PIND3=1;
#endif

return 0;
}

* only ADCL is used because result will be right justified and for precision not more than 8 bit ,ADCL register value is enough as a result for ADC conversion.

* if ADCSRAbits.ADIF is set it means ADC conversion is over. Thus, it is used as a parameter for checking conversion completion.