/*
 * Analog-to-digital converter (ADC) Test Program
 *
 * This program reads and prints out the current voltage of the signal applied
 * to the PORTA:0 pin.
 *
 * This program uses VT100 escape sequences to control the cursor on the
 * Hyperterminal screen, rather than just blasting out line after line of output.
 * Terminal escape sequences allow you to do things like clearing the screen,
 * position the cursor before text output, and changing the text color.
 * Given that '\x1B' is the hex representation of the ASCII escape (ESC) character, 
 * the sequence ESC[2J clears the terminal, and ESCc resets the terminal. 
 *
 * One reference for VT100 escape codes is:
 *   http://ascii-table.com/ansi-escape-sequences-vt-100.php
 *
 * Last Modified 2010/08/19 02:19 (ebw)
 */

#include <avr/io.h>       // for PORTx, DDRx, AD*, etc.
#include <util/delay.h>   // for _delay_ms()
#include <stdio.h>        // for printf()
#include "uart.h"         // for uart_init()

/* functions to declare before their use */
void printWelcome(), printValue();

/*
 * Initialization consists of setting up the ADC and the UART, both of
 * which are described in detail in the ATmega16 datasheet.
 *
 * The ADC is first setup to use AVCC for the ADC voltage reference, then
 * the ADC enabled and the ADC clock is configured to prescale the system clock
 * down by 128 to be slow enough to get full 10-bit accuracy.
 */
void init()
{
    ADMUX  = _BV(REFS0);
    ADCSRA = _BV(ADEN) | _BV(ADPS2) | _BV(ADPS1) | _BV(ADPS0);      

    uart_init();

    printWelcome();
}


int main()
{
    uint16_t adc_level;       // for holding ADC value (if needed multiple times)

    init();

    while (1)
    {
        ADCSRA |= _BV(ADSC);         // start ADC conversion

        while (ADCSRA & _BV(ADSC))
            ;                        // wait until conversion done (bit cleared)

        adc_level = ADC;             // capture the ADC value

        printValue(adc_level);       // for debugging, if we need it

        _delay_ms(100);              // delay 100msec
    }

    return 0;                        // never executed...
} 


/*
 * Print the magic VT100 escape sequence to reset and clear the screen,
 * then the welcome banner.
 */
void printWelcome()
{
    printf("\x1B[2J\x1B\x63");
    printf("Welcome to the ADC test program!");
}


/*
 * Print the magic VT100 escape sequences to move the cursor to <Row2,Column1>,
 * erase the current line, then the requested value.
 */
void printValue(uint16_t value)
{
    printf("\x1B[2;1H\x1B[2K");
    printf("ADC value: %u", value);
}