/*
  ESP8266 Blink by Simon Peter
  Blink the blue LED on the ESP-01 module
  This example code is in the public domain

  The blue LED on the ESP-01 module is connected to GPIO1
  (which is also the TXD pin; so we cannot use Serial.print() at the same time)

  Note that this sketch uses LED_BUILTIN to find the pin with the internal LED
*/

#define WWV_SIGNAL_PIN 14

void ICACHE_RAM_ATTR readLevel();

volatile byte wwvbInState;            // store receiver signal level

byte prevWwvbInState;                 // store previous signal level
unsigned int prevEdgeMillis;          // store time signal was read
byte bitVal;                          // bit decoded 0, 1 or Mark
byte badBit;                          // bad bit, noise detected
byte prevMark;                        // store previous mark bit

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);     // Initialize the LED_BUILTIN pin as an output
  pinMode(WWV_SIGNAL_PIN, INPUT);
  attachInterrupt(digitalPinToInterrupt(WWV_SIGNAL_PIN), readLevel, CHANGE); // fire interrupt on edge detected
  Serial.begin(9600);
  Serial.print("herro booted\n");
}

// the loop function runs over and over again forever
void loop() {
  if (wwvbInState != prevWwvbInState) {
    pulseValue();
    prevWwvbInState = wwvbInState;
  }
  yield();
}

void pulseValue() {
  unsigned int edgeMillis = millis();         // save current time
  badBit = 0;                                 // set noise counter to zero
  if (wwvbInState == 1) {                     // rising edge
    prevEdgeMillis = edgeMillis;              // set previous time to current
  } 
  else {                                    // falling edge
    int pulseLength = edgeMillis - prevEdgeMillis; // calculate pulse length millis
    if (pulseLength < 100) {                  // less than 100ms, noise pulses
      badBit = 1;
    } 
    else if (pulseLength < 400) {           // 800ms carrier drop mark
      bitVal = 2;
    } 
    else if (pulseLength < 700) {           // 500ms carrier drop one
      bitVal = 1;
    } 
    else {                                  // 200ms carrier drop zero
      bitVal = 0;
    }
    if (badBit == 0) {
      printBitVal();
    }
  }
}


void readLevel() {
  wwvbInState = digitalRead(WWV_SIGNAL_PIN);   // read signal level
  digitalWrite(LED_BUILTIN, !wwvbInState); // flash WWVB receiver indicator pin
  yield();

}


void printBitVal() {
  if ((bitVal == 2) && (prevMark == 0)) {
    Serial.print(" : ");

    prevMark = 1;
  } 
  else if ((bitVal == 2) && (prevMark == 1)) {
    Serial.print("\nBit Value: ");
    Serial.print("| ");

    prevMark = 0;
  } 
  else {
    Serial.print(bitVal, DEC);
    prevMark = 0; 
  }
}

/*****************************************************************************
 * Time display functions
 *****************************************************************************/

void printTime() {
  Serial.print("?x00?y0?f"); // movie cursor to line 1 char 1, clear screen
}

// LCD routines to initialize LCD and clear screen
void lcdInit() {           // using P H Anderson Serial LCD driver board
  Serial.print("?G216");   // configure driver for 2 x 16 LCD
  delay(300);
  Serial.print("?BDD");    // set backlight brightness
  delay(300);
  Serial.print("?f");      // clear screen
  Serial.print("?c0");     // set cursor off
}