Hello Guys, This is my first thread post on this forum.
I’m a beginner on Arduino’s programming. I want to ask a question :
How arduino know the pin of each potensio without describing the ADC pin number.
I have a code below (credit to electrosmash):
Thanks Guys
Cheers 
// Licensed under a Creative Commons Attribution 3.0 Unported License.
// Based on RCArduino.Blogspot.com previous work.
// www.electrosmash.com/pedalshield
// tremolo effect produces a variation in the volume of the signal, by mixing the guitar with a sinusoidal waveform.
// potentiometer 0: controls the speed.
// potentiometer 1: controls the deph.
// potentiometer 2: controls the volume level.
int in_ADC0, in_ADC1; //variables for 2 ADCs values (ADC0, ADC1)
int POT0, POT1, POT2, out_DAC0, out_DAC1; //variables for 3 pots (ADC8, ADC9, ADC10)
const int LED = 3;
const int FOOTSWITCH = 7;
const int TOGGLE = 2;
int sample, accumulator, count, LFO;
// Create a table to hold pre computed sinewave, the table has a resolution of 600 samples
#define no_samples 44100
#define MAX_COUNT 160
uint16_t nSineTable[no_samples];//storing 12 bit samples in 16 bit variable.
// create the individual samples for our sinewave table
void createSineTable()
{
for(uint32_t nIndex=0; nIndex<no_samples; nIndex++)
{
// normalised to 12 bit range 0-4095
nSineTable[nIndex] = (uint16_t) (((1+sin(((2.0*PI)/no_samples)*nIndex))*4095.0)/2);
}
}
void setup()
{
createSineTable();
/* turn on the timer clock in the power management controller */
pmc_set_writeprotect(false);
pmc_enable_periph_clk(ID_TC4);
/* we want wavesel 01 with RC */
TC_Configure(TC1,1, TC_CMR_WAVE | TC_CMR_WAVSEL_UP_RC | TC_CMR_TCCLKS_TIMER_CLOCK2);
TC_SetRC(TC1, 1, 238); // sets <> 44.1 Khz interrupt rate
TC_Start(TC1, 1);
// enable timer interrupts on the timer
TC1->TC_CHANNEL[1].TC_IER=TC_IER_CPCS;
TC1->TC_CHANNEL[1].TC_IDR=~TC_IER_CPCS;
/* Enable the interrupt in the nested vector interrupt controller */
/* TC4_IRQn where 4 is the timer number * timer channels (3) + the channel number
(=(1*3)+1) for timer1 channel1 */
NVIC_EnableIRQ(TC4_IRQn);
//ADC Configuration
ADC->ADC_MR |= 0x80; // DAC in free running mode.
ADC->ADC_CR=2; // Starts ADC conversion.
ADC->ADC_CHER=0x1CC0; // Enable ADC channels 0,1,8,9 and 10
//DAC Configuration
analogWrite(DAC0,0); // Enables DAC0
analogWrite(DAC1,0); // Enables DAC0
}
void loop()
{
//Read the ADCs
while((ADC->ADC_ISR & 0x1CC0)!=0x1CC0);// wait for ADC 0, 1, 8, 9, 10 conversion complete.
in_ADC0=ADC->ADC_CDR[7]; // read data from ADC0
in_ADC1=ADC->ADC_CDR[6]; // read data from ADC1
POT0=ADC->ADC_CDR[10]; // read data from ADC8
POT1=ADC->ADC_CDR[11]; // read data from ADC9
POT2=ADC->ADC_CDR[12]; // read data from ADC10
}
void TC4_Handler()
{
// Get the status to clear the interrupt to be fired again.
TC_GetStatus(TC1, 1);
//Increase the sinewave index and/or reset the value.
POT0 = POT0>>1; //divide value by 2 (its too big)
count++;
if (count>=160) //160 chosen empirically
{
count=0;
sample=sample+POT0;
if(sample>=no_samples) sample=0;
}
//Create the Low Frequency Oscillator signal with depth control based in POT1.
LFO=map(nSineTable[sample],0,4095,(4095-POT1),4095);
//Modulate the output signals based on the sinetable.
out_DAC0 =map(in_ADC0,1,4095,1, LFO);
out_DAC1 =map(in_ADC1,1,4095,1, LFO);
//Add volume feature with POT2
out_DAC0 =map(out_DAC0,1,4095,1, POT2);
out_DAC1 =map(out_DAC1,1,4095,1, POT2);
//Write the DACs
dacc_set_channel_selection(DACC_INTERFACE, 0); //select DAC channel 0
dacc_write_conversion_data(DACC_INTERFACE, out_DAC0);//write on DAC
dacc_set_channel_selection(DACC_INTERFACE, 1); //select DAC channel 1
dacc_write_conversion_data(DACC_INTERFACE, out_DAC1);//write on DAC
}