#include <avr/io.h>
#include <stdio.h>

#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

#define HEX__(n) 0x##n##UL

#define B8__(x) ((x&0x0000000FLU)?1:0)  \
  +((x&0x000000F0LU)?2:0)  \
  +((x&0x00000F00LU)?4:0)  \
  +((x&0x0000F000LU)?8:0)  \
  +((x&0x000F0000LU)?16:0) \
  +((x&0x00F00000LU)?32:0) \
  +((x&0x0F000000LU)?64:0) \
  +((x&0xF0000000LU)?128:0)

#define B8(d) ((unsigned char)B8__(HEX__(d)))


#ifndef F_CPU
#define F_CPU 			8000000       	// Mhz 
#endif
#define UART_BAUD_RATE		9600      	// 9600 baud

void uart0_init(void);

int uart_putchar(char c, FILE *stream);
int ADConvert(short Channel, short DivFactor);

void adc_init(void);

int uart_putchar(char c, FILE *stream) {

  if (c == '\n') uart_putchar('\r', stream);
  loop_until_bit_is_set(UCSR0A, UDRE);
  UDR0 = c;

  return 0;
}


void uart0_init(void) {
  unsigned char baudrateDiv;

  baudrateDiv = (unsigned char)((F_CPU+(UART_BAUD_RATE*8L))/(UART_BAUD_RATE*16L)-1);
  	
  UBRR0H = baudrateDiv >> 8;	
  UBRR0L = baudrateDiv;
	
  UCSR0B = (1 << RXEN0) | (1 << TXEN0);
  UCSR0C = (1 << USBS0) | (3 << UCSZ0);

  fdevopen(uart_putchar, NULL);
  printf("\n\nuart0_init();\n");
}

void enable_external_ram (void) __attribute__ ((naked)) __attribute__ ((section (".init1")));

void enable_external_ram(void)
{
  /* 
   * enable external memory, no wait states 
   */
  MCUCR |= _BV(SRE);
}


int main(void)
{
  unsigned char * xram_ptr;

  unsigned int i,j,x;

  uart0_init();

  adc_init();

  TCCR3A = 0x00;

  while (1) {
    //  printf("Hello world!");
    //  read from ADC and output to serial - better serial as library but for now...

    // toggle bank -- PE7/6/5
    
    DDRE=0xff;


    PORTE = 0x7F;

    for (i=0;i<254;i++){

	       xram_ptr = (char *)(0xFF00+i);

	  *xram_ptr = i;

    }

    PORTE = 0x7F;

    xram_ptr = (char *)0xFF00;

    for (i=0;i<254;i++){

      x = *(xram_ptr+i);

	  printf("%d %d\n", i, x);

    }

	//      printf("%d\n", ADConvert(0,2));
  } 
}


void adc_init(void)
{
  /*
  sbi(ADCSRA,ADEN); // enables ADC by setting bit 7 (ADEN) in the ADCSRA
  sbi(ADCSRA,ADFR); // single sample conversion by clearing bit 5 (ADFR) in the ADCSRA
  ADCSRA = ((ADCSRA & B8(11111000)) | B8(00000111)); // selects div by 64 clock prescaler
  ADMUX = ((ADMUX & B8(00111111)) | B8(01000000));         // selects AVCC as Vref
  cbi(ADMUX,ADLAR);       // selects right adjust of ADC result
  ADMUX &= B8(11100000); // selects single-ended conversion on PF0*/
  

  ADCSRA |= (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0); // Set ADC prescalar to 128 - 125KHz sample rate @ 16MHz

  ADMUX |= (1 << REFS0); // Set ADC reference to AVCC
  //  ADMUX |= (1 << ADLAR); // Left adjust ADC result to allow easy 8 bit reading

  // No MUX values needed to be changed to use ADC0

  ADCSRA |= (1 << ADFR);  // Set ADC to Free-Running Mode

  ADCSRA |= (1 << ADEN);  // Enable ADC 

  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)


}


int ADConvert(short Channel, short DivFactor)
{
  int ADresult;/* Result to be returned*/
  
  sbi(ADCSRA, ADSC);               /* Start ADC*/
   loop_until_bit_is_set(ADCSRA, ADIF); /* Wait for ADIF, will happen soon */

  /*
   * Read the input value
   */
  ADresult = ADCL;    /* Read LSB first   */
  ADresult |= ((int)ADCH) << 8;/* then MSB         */

  /*
   * Clear the ADCSRA, including the AD Interrupt Flag (by setting it!)
   */
  //  ADCSRA = 0x10;

  return(ADresult);
}