/*
  How to Use 74HC165 Shift register as serial Asyn input 6 bit
  8 shift per: Idle1-Start0-d0d1d2d3d4d5-Stop1
  Versione UART TX-RX */
const int dataPin = 2; /* Q7 */
const int CP = 5; /* CP */
const int PL = 4; /* PL */
const int Start = 3; /* start Read */
//
const int numBit = 6; /* numero data bit */
const int numShift = 9; /* 8+1 shift: idle1-Start0-d0d1d2d3d4-Stop1 */
volatile uint32_t m0, m1, T, bounce;
volatile uint8_t rby;
volatile int8_t shift_count, bit_count;
#define BAUD 104
#define RECV_OK -1
#define FERR -2

void setup() {
  Serial.begin(9600);
  pinMode(Start, INPUT_PULLUP);
  pinMode(CP, OUTPUT);
  pinMode(PL, OUTPUT);
  digitalWrite(CP, HIGH);
  digitalWrite(PL, HIGH);
  shift_count = bit_count = rby = bounce = 0;
  load_SR();
  //attachInterrupt(digitalPinToInterrupt(Start), StartBit, FALLING);
  //attachInterrupt(digitalPinToInterrupt(dataPin), StartRec, FALLING);

}
void loop() {
  if (shift_count) shifter(); else check_bounce();
  if (bit_count > 0) serialin();
  else if (bit_count < 0) {
    if (bit_count == RECV_OK) Serial.println(rby, BIN);
    else if (bit_count == FERR) Serial.println("Framing Error");
    bit_count = 0;
  }

}
void load_SR() {
  digitalWrite(PL, HIGH); // Per sicurezza - Flash di cattura
  digitalWrite(PL, LOW); // Durata minima impulso (/PL):
  digitalWrite(PL, HIGH); // da 20 a 120 nS
}

void shifter() {
  uint32_t mx = millis();
  if ((mx - m0) > BAUD) {
    m0 += BAUD;
    digitalWrite(CP, LOW); // Per sicurezza Shift avviene da L --> H
    digitalWrite(CP, HIGH); // Durata minima impulso (CP):
    digitalWrite(CP, LOW); // da 20 a 120 nS
    shift_count--;
    //if (shift_count == 0) attachInterrupt(digitalPinToInterrupt(Start), StartBit, FALLING);
  }
}

void serialin() {
  uint32_t mx = millis();
  if ((mx - m1) > T) {
    if (bit_count > numBit) { // Siamo al bit di stop
      if (digitalRead(dataPin)) bit_count = RECV_OK; else bit_count = FERR;
      attachInterrupt(digitalPinToInterrupt(dataPin), StartRec, FALLING);
    } else {
      rby >>= 1;
      if (digitalRead(dataPin)) rby |= 0x80;
      T = BAUD;
      m1 += T;
      bit_count++; // sempre allo stato RUN (count > 0)
    }
  }
}

void StartBit() {
  m0 = millis();
  load_SR();
  shift_count = numShift;
  detachInterrupt(digitalPinToInterrupt(Start)); //disabilita l'interupt fino al termine della trasmissione
}

void StartRec() {
  m1 = millis();
  T = BAUD + BAUD / 2;
  bit_count = 1;
  rby = 0;
  detachInterrupt(digitalPinToInterrupt(dataPin));
}

void check_bounce(){
  uint32_t mx = millis();
  if((mx-bounce) > 400){
    attachInterrupt(digitalPinToInterrupt(Start), StartBit, FALLING);
    bounce += 400;
  }
}