void setup ()
{

  ADCSRA &= ~(bit (ADPS0) | bit (ADPS1) | bit (ADPS2)); // clear prescaler bits
  
  // uncomment as required
  //  ADCSRA |= bit (ADPS0);                               //   2  
  //  ADCSRA |= bit (ADPS1);                               //   4  
  //  ADCSRA |= bit (ADPS0) | bit (ADPS1);                 //   8  
  ADCSRA |= bit (ADPS2);                               //  16 
  //  ADCSRA |= bit (ADPS0) | bit (ADPS2);                 //  32 
  //  ADCSRA |= bit (ADPS1) | bit (ADPS2);                 //  64 
  //  ADCSRA |= bit (ADPS0) | bit (ADPS1) | bit (ADPS2);   // 128
  
  Serial.begin (115200);
  Serial.println ();
  
}  // end of setup

const int ITERATIONS = 10000;
unsigned long totals [6];
const byte lowPort = 0;
const byte highPort = 4;

void loop ()
{
  for (int whichPort = lowPort; whichPort <= highPort; whichPort++)
    totals [whichPort - lowPort] = 0;
  
  unsigned long startTime = micros ();
  for (int i = 0; i < ITERATIONS; i++)
    {
      for (int whichPort = lowPort; whichPort <= highPort; whichPort++)
        {
          int result = analogRead (whichPort);
          totals [whichPort - lowPort] += result;
        } 
    }
  unsigned long endTime = micros ();
  
  for (int whichPort = lowPort; whichPort <= highPort; whichPort++)
    {
      Serial.print ("Analog port = ");
      Serial.print (whichPort);
      Serial.print (", average result = ");
      Serial.println (totals [whichPort - lowPort] / ITERATIONS);
    }
  auto time_taken = endTime - startTime; 
  EKOX(time_taken);

  auto sample_time_ms =  float(time_taken)/ITERATIONS/1000;
  EKOX(sample_time_ms);
  auto sample_rate = 1./sample_time_ms*1000;
  EKOX(sample_rate);
  Serial.println ();
  Serial.flush ();
  exit (0);
}
// end of loop








/***********************************************************************************/
/*  DAC0 and DAC1 output of a sin wave - Frequency of sine = 44.1 KHz / sinsize    */
/***********************************************************************************/

const uint32_t sinsize  = 256 ;   
uint32_t sinus[2][sinsize];
  
volatile uint32_t bufn;

void dac_setup () {

  PMC->PMC_PCER1 = PMC_PCER1_PID38;     // DACC power ON
  DACC->DACC_CR = DACC_CR_SWRST ;       // Reset DACC

  DACC->DACC_MR = DACC_MR_TRGEN_EN                   // Hardware trigger select
                  | DACC_MR_TRGSEL(0b011)            // Trigger by TIOA2
                  | DACC_MR_TAG_EN                   // enable TAG to set channel in CDR
                  | DACC_MR_WORD_WORD                // write to both channels
                  | DACC_MR_REFRESH (1)
                  | DACC_MR_STARTUP_8
                  | DACC_MR_MAXS;

  DACC->DACC_IER |= DACC_IER_TXBUFE;                 // Interrupt used by PDC DMA
                
  DACC->DACC_ACR = DACC_ACR_IBCTLCH0(0b10)           // For DAC frequency > 500 KHz
                   | DACC_ACR_IBCTLCH1(0b10)
                   | DACC_ACR_IBCTLDACCORE(0b01);

  NVIC_EnableIRQ(DACC_IRQn);                         // Enable DACC interrupt

  DACC->DACC_CHER = DACC_CHER_CH0                    // enable channel 0 = DAC0
                    | DACC_CHER_CH1;                 // enable channel 1 = DAC1

  /*************   configure PDC/DMA  for DAC *******************/

  DACC->DACC_TPR  = (uint32_t)sinus[0];         // DMA buffer
  DACC->DACC_TCR  = sinsize;
  DACC->DACC_TNPR = (uint32_t)sinus[1];         // next DMA buffer (circular buffer)
  DACC->DACC_TNCR = sinsize;
  bufn = 1;
  DACC->DACC_PTCR = DACC_PTCR_TXTEN;            // Enable PDC Transmit channel request

}

void DACC_Handler() {
  
  uint32_t status = DACC->DACC_ISR;   // Read and save DAC status register
  if (status & DACC_ISR_TXBUFE) {     // move DMA pointer to next buffer
    bufn = (bufn + 1) & 1;
    DACC->DACC_TNPR = (uint32_t)sinus[bufn];
    DACC->DACC_TNCR = sinsize;
  }
}

void tc_setup() {

  PMC->PMC_PCER0 |= PMC_PCER0_PID29;                      // TC2 power ON : Timer Counter 0 channel 2 IS TC2
  TC0->TC_CHANNEL[2].TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK2  // MCK/8, clk on rising edge
                              | TC_CMR_WAVE               // Waveform mode
                              | TC_CMR_WAVSEL_UP_RC        // UP mode with automatic trigger on RC Compare
                              | TC_CMR_ACPA_CLEAR          // Clear TIOA2 on RA compare match
                              | TC_CMR_ACPC_SET;           // Set TIOA2 on RC compare match


  TC0->TC_CHANNEL[2].TC_RC = 238;  //<*********************  Frequency = (Mck/8)/TC_RC = 44.1 KHz
  TC0->TC_CHANNEL[2].TC_RA = 40;  //<********************   Any Duty cycle in between 1 and TC_RC

  TC0->TC_CHANNEL[2].TC_CCR = TC_CCR_SWTRG | TC_CCR_CLKEN; // Software trigger TC2 counter and enable
}

void setup() {

  for(int i = 0; i < sinsize; i++) 
    {
   uint32_t chsel = (0<<12) | (1<<28);                      // LSB on DAC0, MSB on DAC1 !!
   sinus[0][i]  = 2047*sin(i * 2 * PI/sinsize) + 2047;      //  0 < sinus [i] < 4096
   sinus[1][i] = sinus[0][i] |= sinus[0][i] <<16 | chsel;   // two buffers formated
                                                            // MSB [31:16]on channel 1
                                                            // LSB [15:0] on chanel 0
    }
  tc_setup();
  dac_setup();
}

void loop() {

}