// inslude the SPI library:
#include <SPI.h>
int data[19] = {0};
byte data_max[19] = {0};
int threshold[] = {100, 100, 100, 60, 100, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210};
byte steps[19] = {0};
byte mapping[19] = {33, 35, 36, 38, 40, 42, 43, 45, 47, 48, 50, 52, 54, 55, 57, 59, 60, 62, 64};
byte note_off_flag = 0;

void setup() {
  pinMode(A5,OUTPUT);
  digitalWrite(A5,HIGH);
  pinMode(10, OUTPUT); // SS pin
  pinMode(3,OUTPUT); // oscillator pin
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV64); // 250kHz
  Serial.begin(31250); // midi baud rate
  TCCR2A = 0x12; // toggle oc2b for 50% duty cycle
  TCCR2B = 0x01; // T_ck = CPU_ck/1
  OCR2A = 0x28; // f = T_ck/(2*OCR2A) = ~200kHz @ 0x28
  // calibration code
  delay(10000);
  for (int i = 0; i < 2000; i++) { // 2000*14ms = 28s
    digitalWrite(10,LOW);
    delay(1);
    for (byte i = 0; i < 19; i++) {
      data[i] = SPI.transfer(0); // if doing 16b, change to "SPI.transfer(0)<<8;"
    }
    digitalWrite(10,HIGH);
    delay(12);
    for (byte i = 0; i < 19; i++) {
      if (data[i] > data_max[i]) data_max[i] = data[i];
    }
  }
  for (byte i = 0; i < 19; i++) {
    threshold[i] = data_max[i] + 10;
  }

  Serial.write(0xb0); // send all notes off
  Serial.write(120);
  Serial.write(0);
  delay(3000);
  for (byte i = 0; i < 20; i++) data[i] = 0;
}

void loop() {
  digitalWrite(10,LOW);
  delay(1);
  for (byte i = 0; i < 19; i++) {
    data[i] = SPI.transfer(0); // if doing 16b, change to "SPI.transfer(0)<<8;"
  }
  digitalWrite(10,HIGH);
  delay(12); // just in case b/c of 8b values
  // this is for doing 16b values
  // remember to change all values to unsigned int
/*
  delay(1);
  digitalWrite(10,LOW);
  delay(1);
  for (byte i = 0; i < 19; i++) {
    data[i] += SPI.transfer(0);
  }
  digitalWrite(10,HIGH);
*/
  for (byte i = 0; i < 19; i++) {
    int k = data[i] - threshold[i];
    byte j = steps[i];
    if (k > 0) {
      //k = data[i];
      //if (k > 127) k = 127;
      //k = (k - 64) << 1;
      if (j == 0) steps[i] = 1;
      else if (j == 1) { // note on
        steps[i] = 2;
        Serial.write(0x90);
        Serial.write(mapping[i]);
        Serial.write(70);
      }
//      else { // polyphonic aftertouch
//        Serial.write(0xa0);
//        Serial.write(mapping[i]);
//        Serial.write(k);
//      }
    }
    else {
      if (j == 1) steps[i] = 0;
      else if (j == 2) steps[i] = 3;
      else if (j == 3) {
        steps[i] = 0;
        Serial.write(0x80);
        Serial.write(mapping[i]);
        Serial.write(0);
      }
    }
  }
/*  byte m = 0;
  for (byte i = 0; i < 19; i++) {
    m += steps[i];
  }
  if ((m == 0) && (note_off_flag == 0)) {
    note_off_flag = 1;
    Serial.write(0xb0); // send all notes off
    Serial.write(120);
    Serial.write(0);
  }
  else if (m != 0) note_off_flag = 0;
  */
}

// all notes off
/*
  Serial.write(0xb0);
  Serial.write(120);
  Serial.write(0);
*/