/*********************************

This code provide you to print an

analog value on ADC channel 0

to the USART of an ATmega 328p

by Mathieu Souchet

*********************************/

#define F_CPU 16000000UL

#include <avr/io.h>

#include <util/delay.h>

#define BAUDRATE 9600

#define BAUD_PRESCALLER (((F_CPU / (BAUDRATE * 16UL))) - 1)

//Declaration of our functions

void USART_init(void);

void adc_init(void);

unsigned char USART_receive(void);

void USART_send( unsigned char data); //Send a char

void USART_putstring(char* StringPtr); //Send a string

uint16_t adc_value; //Variable used to store

uint16_t read_adc(uint8_t channel);

char buffer[5];

int main(void){

USART_init(); //Call the USART initialization code

adc_init();

while(1){ //Infinite loop

adc_value=read_adc(0);

itoa(adc_value,buffer,10);

USART_putstring(buffer); //Pass the string to the USART_putstring function and sends it over the serial

USART_send('\r'); //Carriage return

USART_send('\n'); //Linefeed

_delay_ms(500);

}

return 0;

}

//Initialise USART

void USART_init(void){

UBRR0H = (uint8_t)(BAUD_PRESCALLER>>8);

UBRR0L = (uint8_t)(BAUD_PRESCALLER);

UCSR0B = (1<<RXEN0)|(1<<TXEN0);

UCSR0C = (3<<UCSZ00);

}

unsigned char USART_receive(void){

while(!(UCSR0A & (1<<RXC0)));

return UDR0;

}

//Send a char via USART

void USART_send( unsigned char data){

while(!(UCSR0A & (1<<UDRE0)));

UDR0 = data;

}

//Send a String via USART

void USART_putstring(char* StringPtr){

while(*StringPtr != 0x00){

USART_send(*StringPtr);

StringPtr++;}

}

//Initialise ADConverter

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

}

//REturn a value from the ADC

uint16_t read_adc(uint8_t channel){

ADMUX = (ADMUX & 0xF0) | (channel & 0x0F); //Select ADC channel with safety mask

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

}