Colony » Colony Scout

#include <avr/io.h>

#include "analog.h"

int line_threshold = 150;

int line_read(int which);

void line_update(int* values);

int line_locate(int* values);

void analog_init(void)

{

  // ADMUX register

  // Bit 7,6 - Set voltage reference to AVcc (0b01)

  // Bit 5 - ADLAR not set

  // Bit 4 - X

  // Bit 3:0 - Current channel

  ADMUX = _BV(REFS0);

  // ADC Status Register A

  // Bit 7 - ADEN  analog enable set

  // Bit 6 - ADSC  start conversion bit not set

  // Bit 5 - ADATE enable auto trigger (for free running mode) not set

  // Bit 4 - ADIF  ADC interrupt flag

  // Bit 3 - ADIE  enable ADC interrupt (required for free-running mode)

  // Bits 2-0 - ADPS set to 8 MHz / 64 = 125 kHz (should be 50-200 kHz)

  ADCSRA = _BV(ADEN) | _BV(ADPS2) | _BV(ADPS1);

  // Set line sensor mux lines PD2, PD3, and PB3 (MOSI) to output

  DDRD |= _BV(DDD2) | _BV(DDD3);

  DDRB |= _BV(DDB3);

}

int analog_read(int which)

{

  ADMUX = (ADMUX & 0xF0) | (which & 0x0F);

  // Start the conversion

  ADCSRA |= _BV(ADSC);

  // Wait for the conversion to finish

  while (ADCSRA & _BV(ADSC));

  int adc_l = ADCL;

  int adc_h = ADCH;

  return ((adc_h << 8) | adc_l);

}

int line_read(int which)

{

  PORTD = (PORTD & 0xF3) | ((which & 3) << 2);

  PORTB = (PORTB & 0XF7) | ((which & 4) << 1);

  // For loop is used only as a delay to allow mux to settle

  volatile int i;

  for(i=0; i < 5; i++);

  return analog_read(ADC_LINE);

}

void line_update(int* values)

{

  int i;

  for(i = 0; i<5; i++)

    values[i] = line_read(i) < line_threshold ? LWHITE : LBLACK;

}

int line_locate(int* values)

{

  int i;

  int wsum = 0;

  int count = 0;

  for(i = 0; i < 5; i++)

  {

    count += values[i] / 2;

    wsum += i * values[i];

  }

  if (count == 0)

    return NOLINE;        

  if (count == 5)

    return FULL_LINE;

  return (wsum/count)-4;

}

int line_read_pos(void)

{

  int values[5];

  line_update(values);

  return line_locate(values);

}

void line_set_threshold_high(uint8_t threshold)

{

  line_threshold = ((int)(threshold & 3) << 8) | (line_threshold & 0xFF);

}

void line_set_threshold_low(uint8_t threshold)

{

  line_threshold = (line_threshold & 0x300) | (uint16_t) threshold;

}