#define DAC_SW    48

#define DAC_LED0  46
#define DAC_LED1  50

int dac_select = 0;
bool dac_sw_pressed = false;

#define ADC_SW    42

#define ADC_LED0  44
#define ADC_LED1  40

#define LP_IN_CLK   6
#define LP_OUT_CLK  7

int adc_select = 0;
bool adc_sw_pressed = false;

//max 12
#define BITS    12

//max 150000
#define FILT_FREQ 150000

void setup() {
  Serial.begin(115200);

  //analog
  analogWriteResolution(BITS);
  analogReadResolution(BITS);

  //DAC
  pinMode(DAC_SW, INPUT);
  digitalWrite(DAC_SW, HIGH);  
  
  pinMode(DAC_LED0, OUTPUT);
  digitalWrite(DAC_LED0, HIGH);
  pinMode(DAC_LED1, OUTPUT);

  pinMode(DAC0, OUTPUT);
  pinMode(DAC1, OUTPUT);

  //ADC
  pinMode(ADC_SW, INPUT);
  digitalWrite(ADC_SW, HIGH);  
  
  pinMode(ADC_LED0, OUTPUT);
  digitalWrite(ADC_LED0, HIGH);
  pinMode(ADC_LED1, OUTPUT);

  //PWM
  pinMode(LP_IN_CLK, OUTPUT);
  pinMode(LP_OUT_CLK, OUTPUT);

  //50%
  analogWrite(LP_IN_CLK, pow(2, BITS) / 2);
  analogWrite(LP_OUT_CLK, pow(2, BITS) / 2);

  PWMC_ConfigureClocks(FILT_FREQ * PWM_MAX_DUTY_CYCLE, 0, VARIANT_MCK);

}

bool check_switch(int in, int led0, int led1, int * select, bool * pressed)
{
  if (digitalRead(in) == 0 && *pressed == false)
  {
    *pressed = true;
    *select = !(*select);

    digitalWrite(led0, *select == 0);
    digitalWrite(led1, *select == 1);

    return true;
  }
  
  if (digitalRead(in) == 1)
    *pressed = false;
    
  return false;
}

long x = 0;
int64_t y = 0;

int x_ptr = 0;

#define TAPS 51

//**********************************************************************


/* //1. floating point parameters
#define MUL 1
float x_old[TAPS];
float b[TAPS] = {...};
//*/

/*//2. fixed point parameters 1000000
#define MUL 1000000
int64_t x_old[TAPS];
const int64_t b[TAPS] = {...};
//*/

/*//3. fixed point parameters 1048576
#define MUL 1048576
int64_t x_old[TAPS];
const int64_t b[TAPS] = {...};
//*/



//**********************************************************************

void loop() {
  check_switch(DAC_SW, DAC_LED0, DAC_LED1, &dac_select, &dac_sw_pressed);
  check_switch(ADC_SW, ADC_LED0, ADC_LED1, &adc_select, &adc_sw_pressed);

  if (adc_select == 0)
    x = analogRead(A0);
  else
    x = analogRead(A1);

  x -= 2048;

  x_old[x_ptr] = x * MUL;

  y = 0;
  for (int i = 0; i < TAPS; i++)
  {
    int index;
    
    if (i <= x_ptr)  
      index = x_ptr - i;
    else
      index = TAPS + x_ptr - i;
  
    y += (x_old[index] * b[i]) / ((int64_t)MUL * (int64_t)MUL);
  }
  x_ptr = (x_ptr + 1) % TAPS;

  y += 2048;

  if (dac_select == 0)
    analogWrite(DAC0, y);
  else
    analogWrite(DAC1, y);
}