int maxpix = 1000;  // maximálna poloha v pixeloch
int stpx = 16;  // lineárna závislosť medzi krokmi a bodmi
int stlf = 205;  // množstvo krokov na posunutie o jeden pixelový riadok

byte naTlac[1000];  // alokovaných 1000 bajtov, kde sa budú písať hodnoty

long step = 0;  // kroky motora tlačovej hlavy
long tarstep = 0;  // cieľová pozícia motora tlačovej hlavy
long printpix = 0; // pixel na tlač
long pixel = 0;  // horizontálna poloha v pixeloch
byte pxlnfeed = 0;  // má sa posunúť riadok v úrovni pixelov?
long stplnfdamnt = 0;  // relatívne množstvo krokov na posuv papiera o riadok
byte val = 0;  // hodnota čítaná z array naTlac
byte toprint = 0; // má sa tlačiť? Platí len pre jeden riadok pixelov
long retstep = 0;  // kroky návratu tlačovej hlavy
byte printdir = 0;  // smer tlače
unsigned int clearing = 0;
const byte pins[8] = {6, 7, 8, 9, 10, 11, 12, 13};   //pins for bit outputs, in bit order
const byte Numpins = sizeof(pins);

void setup() {
  pinMode(2, OUTPUT);  // stepper 1 dir
  pinMode(3, OUTPUT);  // stepper 1 step
  pinMode(4, OUTPUT);  // stepper 2 step
  pinMode(5, INPUT_PULLUP);  // koncový kalibračný spínač
  for (int pinNum = 0; pinNum < Numpins; pinNum++) {
    pinMode(pins[pinNum], OUTPUT); //writes a 1 to a pin that is a zero in the received byte
  }
  Serial.begin(9600);
  Serial.println();  // tento riadok môžete vynechať
  //shlulls();
  for (int v = 0; v < maxpix - 1; v = v + 1) { //This will clear pixels 0 -> 998  - is that the intent?  Pixel 999(i.e. the 1000th pixel, is untouched)
    naTlac[v] = 0;
  }
}

void loop() {
  if (Serial.available()) {
    naTlac[printpix] = Serial.read();
    printpix = printpix + 1;
  }
  if (printpix >= maxpix) {
    Serial.write(0x13);
    printpix = 0;
    toprint = 1;
  }
  if (toprint == 1 && printdir == 0)     stepMovePrint();
  if (toprint == 1 && printdir == 1)     stepMovePrintReverse();
  while (clearing < maxpix) {
    naTlac[clearing] = 0;
    clearing = clearing + 1;
  }
}

void stepMovePrint() {  // tlačenie jedného riadku
  tarstep = pixel * stpx;
  digitalWrite(2, LOW);
  if (toprint == 1) {
    while (pixel < maxpix) {
      tarstep = pixel * stpx;
      val = naTlac[pixel];
      while (tarstep > step) {
        tarstep = pixel * stpx;
        digitalWrite(3, HIGH);
        delayMicroseconds(40);
        digitalWrite(3, LOW);
        delayMicroseconds(40);
        if (tarstep - step <= stpx - 10) {
          for (int pinNum = 0; pinNum < Numpins; pinNum++) {
            digitalWrite(pins[pinNum], LOW);  //writes a 1 to a pin that is a zero in the received byte
          }
        }
        else prhdwt();
        step = step + 1;
      }
      if (tarstep <= step) pixel = pixel + 1;
    }
  }
  toprint = 0;
  digitalWrite(5, LOW);
  printdir = 1;
  stepLinefeed();
}

void stepLinefeed() {
  stplnfdamnt = stlf;
  while (stplnfdamnt >= 1) {
    digitalWrite(4, HIGH);
    delayMicroseconds(100);
    digitalWrite(4, LOW);
    delayMicroseconds(100);
    stplnfdamnt = stplnfdamnt - 1;
  }
  printpix = 0;
  clearing = 0;
  for (int i = 0; i < maxpix; i = i + 1) naTlac[i] = 0;
  Serial.write(0x11);
}

void stepMovePrintReverse() {  // tlačenie jedného riadku
  tarstep = pixel * stpx;
  digitalWrite(2, HIGH);
  if (toprint == 1) {
    while (pixel >= 0) {
      tarstep = pixel * stpx;
      if (pixel > -1) val = naTlac[pixel];
      if (pixel == -1) val = naTlac[0];

      while (tarstep < step) {
        tarstep = pixel * stpx;
        digitalWrite(3, HIGH);
        delayMicroseconds(40);
        digitalWrite(3, LOW);
        delayMicroseconds(40);
        if (step - tarstep <= stpx - 10) {
          for (int pinNum = 0; pinNum < Numpins; pinNum++) {
            digitalWrite(pins[pinNum], LOW);  //writes a 1 to a pin that is a zero in the received byte
          }
        }
        else prhdwt();
        step = step - 1;
      }
      if (tarstep >= step) pixel = pixel - 1;
    }
  }
  digitalWrite(5, LOW);
  toprint = 0;
  printdir = 0;
  stepLinefeed();
}

void shlulls() {
  digitalWrite(2, HIGH);
  while (digitalRead(6) == HIGH) {
    digitalWrite(3, HIGH);
    delayMicroseconds(2500);
    digitalWrite(3, LOW);
    delayMicroseconds(2500);
  }
  tarstep = 0;
  step = 0;
  pixel = 0;
  printpix = 0;
  while (step <= 400) {
    digitalWrite(2, LOW);
    digitalWrite(3, HIGH);
    delayMicroseconds(250);
    digitalWrite(3, LOW);
    delayMicroseconds(250);
    step = step + 1;
  }
}

void prhdwt() { /* Print head write (writes a byte to the whole printhead) */
  byte num1 = ~naTlac[pixel];
  for (int pinNum = 0; pinNum < Numpins; pinNum++ ) {
    digitalWrite(pins[pinNum], num1 & 0b00000001);  //writes a 1 to a pin that is a zero in the received byte
    num1 = num1 >> 1;
  }
}