Write a program to measure the analog voltage on the PCO(ADCO) pin using the ADC

Question

Write a program to measure the analog voltage on the PCO(ADCO) pin using the ADC peripheral with V_ref selected to be AV_cc. Using a voltage source, apply a DC voltage to ADC0 and record measurements at 20 different input voltages between 0 and 5 volts. Use a multimeter to measure the actual input voltage V_in. Measure the supply voltage AV_cc on the 5V pin. Provide a table that includes the measured (by multimeter) voltage V_in, the expected ADC value for V_in, the recorded ADC value (a 10-bit unsigned integer), and the voltage that the ADC value represents. Do your measurements match your expectations? How do you expect the measurement from Part 1 to affect these results? Explain your answer. Plot the recorded ADC value (y-axis) versus the measured input voltage V_in (x-axis).

Explanation / Answer

Ans:

// program for reading and displaying

#include <avr/io.h>

// includes lcd.h

#include "lcd.h"

void InitADC()

{

ADMUX=(1<<REFS0); // For Aref=AVcc;

ADCSRA=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0); //Rrescalar div factor =128

}

uint16_t ReadADC(uint8_t ch)

{

ch=ch&0b00000111;

ADMUX|=ch;

ADCSRA|=(1<<ADSC);

while(!(ADCSRA & (1<<ADIF)));

ADCSRA|=(1<<ADIF);

return(ADC);

}

void Wait()

{

uint8_t i;

for(i=0;i<20;i++)

_delay_loop_2(0);

}

void main()

{

uint16_t adc_result;

LCDInit(LS_BLINK|LS_ULINE);

LCDClear();

InitADC();

LCDWriteString("ADC Test");

LCDWriteStringXY(0,1,"ADC=");

while(1)

{

// for reading values, channel-0

adc_result=ReadADC(0);

// lcd values

LCDWriteIntXY(4,1,adc_result,4);

Wait();

}

}

// for measuring

#define BATTERY_VOLTAGE(v)

do {

ADCCON2 = 0x2F;

ADCCON1 = 0x76;

while(!(ADCCON1 & 0x80));

v = ADCL;

// values

v |= (((unsigned int)ADCH) << 5);

} while(0)

#define CONST 0.0183195

unsigned char getBatteryVoltage(void) {

unsigned int adcValue;

SAMPLE_BATTERY_VOLTAGE(adcValue);

adcValue >>= 4;

return CONST * adcValue;

}

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