ADC

[neena]

Hello,

 

I am using atmega128 board. I wanted a  C code for adc anolog values range from 0-5V. And also how to check the output on avr studio 4.

 

Please help.

[Jason Jordon]

I found this code:

 

#include <avr/io.h> // include I/O definitions (port names, pin names, etc) 

#include “global.h” // include our global settings 

// 

//

---

Defines

---

 

#define BV(bit) (1<<(bit)) // Byte Value => converts bit into a byte value. One at bit location. 

#define cbi(reg, bit) reg &= ~(BV(bit)) // Clears the corresponding bit in register reg 

#define sbi(reg, bit) reg |= (BV(bit)) // Sets the corresponding bit in register reg 

// 

//

---

Function Prototypes

---

 

void adc_init(void); // Will set up the registers for A/D conversion 

//

---

Begin Code

---

 

int main(void) 

{ 

 unsigned short adc_result; // Just a variable to hold the result 

 adc_init(); // Call the init function 

 DDRF = 0x00; // configure a2d port (PORTF) as input so we can receive analog signals 

 PORTF = 0x00; // make sure pull-up resistors are turned off (else we’ll just read 0xCFF) 

 while(1) 

 { 

 sbi(ADCSRA,ADSC); // start a conversion by writing a one to the ADSC bit (bit 6) 

 while(ADCSRA & 0b01000000); // wait for conversion to complete (bit 6 will change to 0) 

 adc_result = ((ADCL) | ((ADCH)<<); // 10-bit conversion for channel 0 (PF0) 

 } 

 return 0; 

} // end main() 

// 

void adc_init(void) 

{ 

 sbi(ADCSRA,ADEN); // enables ADC by setting bit 7 (ADEN) in the ADCSRA 

 cbi(ADCSRA,ADFR); // single sample conversion by clearing bit 5 (ADFR) in the ADCSRA 

 ADCSRA = ((ADCSRA & 0b11111000) | 0b00000110); // selects div by 64 clock prescaler 

 ADMUX = ((ADMUX & 0b00111111) | 0b01000000); // selects AVCC as Vref 

 cbi(ADMUX,ADLAR); // selects right adjust of ADC result 

 ADMUX &= 0b11100000; // selects single-ended conversion on PF0 

} 

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