Bohdan Kondratenko

ADC.c

					
#include "ADC.h"

/* Setting both ADC and Timer 0 channel A to the Mode for sound capturing 
 * WARNING! Uses Timer 0 channel A
 * Reason for usage of Tim 0 channel A triggering - triggering frequency can be adjusted to the requirements (TIMA PWM TOP = OCRA)
 */
my_bool capture_start(unsigned long freq_HZ)
{
	//char debug_str[16];
	
  if (freq_HZ > 31250) // if this is true than the Timer will not be able to generate the frequncy
  {
     return LOW;
  }
	
  /*********************** ADC Setting ***********************/
  ADCSRA = 0;           // The registers are being first reset, co clean the pre-settings from Arduino IDE
  ADCSRA |=  (1<<ADEN) | (1<<ADATE) | (1<<ADIE) | (1<<ADPS1);   // | bit (ADPS0) | bit (ADPS0);  // turn ADC on, want interrupt on completion (switch off ADEN when going on sleep mode)
  /* ADCSRA Bits:
   * 7) ADEN: ADC Enable
   * 6) ADSC: ADC Start Conversion
   * 5) ADATE: ADC Auto Trigger Enable
   * 4) ADIF: ADC Interrupt Flag
   * 3) ADIE: ADC Interrupt Enable
   * 2-0) ADPS2:0: ADC Prescaler Select Bits (to be adjusted) (division factor between the system clock frequency and the input clock to the ADC) 010 -> 4
   */
  
  ADMUX = 0;
  ADMUX |= (1<<REFS0) | (1<<ADLAR); //reference source - supply voltage, input to read - Micro, Left alighn for receive (register ADCH)
  /* ADMUX Bits:
  * 7-6) REFS1:0: Reference Selection Bits (00 = AREF, internal VREF turned off; 01 = AVCC with external capacitor at AREF pin)
  * 5) ADLAR: ADC Adjust Result (1 - Left, 0 - Right)
  * 4)  Res: Reserved Bit
  * 3-0) MUX3:0: Analog Channel Selection Bits (for my input A0 or AC0 - 0000)
  */  
  
  ADCSRB = 0;
  ADCSRB |= (1<<ADTS1) | (1<<ADTS0); 
  /* ADC Control and Status Register
   * 2-0) ADTSx – ADC Auto Trigger Source 011 - Timer/Counter 0 Compare match A
   */

  /*********************** TIM0 (channel A) Setting ************************/ 
  TIMSK0 = 0;
  TIMSK0 |= (1<<OCIE0A);
  /* TIMSK0 – Timer/Counter0 Interrupt Mask Register
   * 2) OCIE0B: Timer/Counter0 Output Compare Match B Interrupt Enable
   * 1) OCIE0A: Timer/Counter0 Output Compare Match A Interrupt Enable
   * 0) TOIE0: Timer/Counter0, Overflow Interrupt Enable
   */ 
 
  
  TCCR0A = 0;
  TCCR0B = 0;
  TCCR0A |= (1<<WGM00) | (1<<WGM01);
  TCCR0B |= (1<<WGM02);            
  /* Timer/Counter1 Control Register A and B
   * 7) ICNC1: Input Capture Noise Canceler
   * 6) ICES1: Input Capture Edge Select
   * 5) Reserved Bit 
   * 4-3) WGM02:0: Waveform Generation Mod 111 - FAST PWM Mode, Top - OCR0A Register 
   * 2-0) CS12:0: Clock Select 001 - Prescaler 1 (to be adjusted);
   */

   /*** interrupt frequency (Hz) = (MCU clock speed 16,000,000Hz) / (prescaler * (compare match register + 1)) ***/
   /* compare match register = (MCU clock speed 16,000,000Hz) / interrupt frequency (Hz) / prescaler - 1 */ 
   
  uint8_t Val = F_CPU/freq_HZ/64-1;		// 64 - the prescaler!!
  OCR0A = Val;
  Val = OCR0A;
  
  //sprintf(debug_str, "OCR0A: %u\n", OCR0A);
  //print_str(debug_str);
  
  /*** Start Conversion! ***/
  TCNT0 = 0;
  ADCSRA |= (1<<ADSC);
  TCCR0B |= (1<<CS01) | (1<<CS00);
  
  return HIGH;
}

void capture_stop(void)
{
  ADCSRA = 0;  // turn off ADC
  
  //char str[10];
  //sprintf(str, "\nADC STOP");
  //print_str(str);
  
  //Serial.println();
  //Serial.println("ADC STOP");
}