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/*
  Arduino based Digital Setting Circle

 Michael Fulbright 2010-06-06

 <mike.fulbright at pobox.com>

 Feel free to modify and share - please let me know if you make any changes so I can keep my version up to date

 2010-06-06:  Initial relase - supports 2X encoding

 */

// constants won't change. They're used here to
// set pin numbers:

const int AZ_enc_A = 6;  // digital pin 6 = PD6
const int AZ_enc_B = 7;  // digital pin 7 = PD7

const int ALT_enc_A = 9;   // digital pin 9 = PB1
const int ALT_enc_B = 10;  // digital pin 10 = PB2

const int RES = 4000;  // resolution of encoders

byte beenAligned = 0; 

long ALT_pos = RES/2;  // initial position of encoders is
long AZ_pos = RES/2;   // half their resolution

void setup() {

  // initialize the encoder inputs
  pinMode(ALT_enc_A, INPUT);
  pinMode(ALT_enc_B, INPUT);
  pinMode(AZ_enc_A, INPUT);
  pinMode(AZ_enc_B, INPUT);

  Serial.begin(9600);

  // Pin change interrupt control register - enables interrupt vectors
  // Bit 2 = enable PC vector 2 (PCINT23..16)
  // Bit 1 = enable PC vector 1 (PCINT14..8)
  // Bit 0 = enable PC vector 0 (PCINT7..0)
  PCICR |= (1 << PCIE2);
  PCICR |= (1 << PCIE0);

  // Pin change mask registers decide which pins are enabled as triggers
  PCMSK2 |= (1 << PCINT23);  // arduino pin 7 = PD7 = az encoder A
  PCMSK0 |= (1 << PCINT1);   // arduino pin 9 = PB1 = alt encoder A

  // enable interrupts
  interrupts();
}

void loop(){


  // see if command sent and reply if appropriate
  //

  byte inchar;
  while (!Serial.available())
  {
    delay(50);
  }
  inchar = Serial.read();

  // throw away rest of command - we don't need it
  Serial.flush();

  if (inchar == 'Q')
  {
    printEncoderValue(AZ_pos);
    Serial.print("\t");
    printEncoderValue(ALT_pos);
    Serial.print("\r");
  }
  else if (inchar == 'R' || inchar == 'Z' || inchar == 'I' || inchar == 'z')
  {
    // ignore command - just return proper code
    if (inchar == 'R' || inchar == 'I') 
      Serial.print("R");
    else if (inchar == 'Z')
      Serial.print("*");
    else if (inchar == 'z')
      Serial.print("r");
  }
  else if (inchar == 'r')
  {
    // print out resolution - hardcoded to 4000 tics/rev
    Serial.print("04000\t04000\r");
  }
  else if (inchar == 'V')
  {
    //version
    Serial.print("V1.0.0\r");
  }
  else if (inchar == 'T')
  {
    // test mode - output resolutions and error count
    Serial.print("04000,04000,00000\r");
  }
  else if (inchar == 'q')
  {
    // error count
    Serial.print("00000\r");
  }
  else if (inchar == 'P')
  {
    // encoder power up
    Serial.print("P");
  }
  else if (inchar == 'p')
  {
    //
    // dave eks error command
    Serial.print("00");
  }
  else if (inchar == 'h')
  {
    // report resolution in Dave Eks format
    Serial.write(0xA0);
    Serial.write(0x0F);
    Serial.write(0xA0);
    Serial.write(0x0F);
  }
  else if (inchar == 'y')
  {
    // report encoders in Dave Eks format
    printHexEncoderValue(ALT_pos);
    printHexEncoderValue(AZ_pos);
  } 
  else if (inchar == 'a')
  {
    if (beenAligned)
      Serial.print("Y");
    else
      Serial.print("N");
  }
  else if (inchar == 'A')
  {
    beenAligned = 1;
  }

#ifdef DEBUG
  Serial.print(digitalRead(AZ_enc_A));
  Serial.print(" ");
  Serial.print(digitalRead(AZ_enc_B));
  Serial.print(" ");
  Serial.print(digitalRead(ALT_enc_A));
  Serial.print(" ");
  wi
    Serial.print(digitalRead(ALT_enc_B));
  Serial.print("\r");

  //return;

  Serial.print(AZ_pos);
  Serial.print(" ");
  Serial.print(ALT_pos);
  Serial.print("\r");

  delay(500);
#endif


}


// print encoder value with leading zeros
void printEncoderValue(long val)
{
  unsigned long aval;

  if (val < 0)
    Serial.print("-");
  else
    Serial.print("+");

  aval = abs(val);

  if (aval < 10)
    Serial.print("0000");
  else if (aval < 100)
    Serial.print("000");
  else if (aval < 1000)
    Serial.print("00");
  else if (aval < 10000)
    Serial.print("0");

  Serial.print(aval); 
}

void printHexEncoderValue(long val)
{
  byte low, high;

  high = val / 256;

  low = val - high*256;

  Serial.write(low);
  Serial.write(high);

  return;
}


// we have to write our own interrupt vector handler..
ISR(PCINT2_vect){

  if (digitalRead(AZ_enc_A) == digitalRead(AZ_enc_B))
  {
    AZ_pos++;
    if (AZ_pos >= RES)
      AZ_pos = 0;
  }
  else
  {
    AZ_pos--;

    if (AZ_pos < 0)
      AZ_pos = RES - 1;
  }
}


ISR(PCINT0_vect){

  if (digitalRead(ALT_enc_A) == digitalRead(ALT_enc_B))
  {
    ALT_pos++;

    if (ALT_pos >= RES)
      ALT_pos = 0;
  }
  else
  {
    ALT_pos--;

    if (ALT_pos < 0)
      ALT_pos = RES - 1;
  }

}