/* 1-Wire Interface v2

   David Johnson-Davies - www.technoblogy.com - 19th August 2018
   ATtiny85 @ 8 MHz (internal oscillator; BOD disabled)
   
   CC BY 4.0
   Licensed under a Creative Commons Attribution 4.0 International license: 
   http://creativecommons.org/licenses/by/4.0/
*/

// One Wire Protocol **********************************************

// Buffer to read data or ROM code
static union {
  uint8_t DataBytes[9];
  unsigned int DataWords[4];
};

const int OneWirePin = 3;

const int ReadROM = 0x33;
const int MatchROM = 0x55;
const int SkipROM = 0xCC;
const int ConvertT = 0x44;
const int ReadScratchpad = 0xBE;

inline void PinLow () {
  DDRB = DDRB | 1<<OneWirePin;
}

inline void PinRelease () {
  DDRB = DDRB & ~(1<<OneWirePin);
}

// Returns 0 or 1
inline uint8_t PinRead () {
  return PINB>>OneWirePin & 1;
}

void DelayMicros (int micro) {
  TCNT1 = 0; TIFR = 1<<OCF1A;
  OCR1A = (micro>>1) - 1;
  while ((TIFR & 1<<OCF1A) == 0);
}

void LowRelease (int low, int high) {
  PinLow();
  DelayMicros(low);
  PinRelease();
  DelayMicros(high);
}

uint8_t OneWireSetup () {
  TCCR1 = 0<<CTC1 | 0<<PWM1A | 5<<CS10;  // CTC mode, 500kHz clock
  GTCCR = 0<<PWM1B;
 }

uint8_t OneWireReset () {
  uint8_t data = 1;
  LowRelease(480, 70);
  data = PinRead();
  DelayMicros(410);
  return data;                         // 0 = device present
}

void OneWireWrite (uint8_t data) {
  int del;
  for (int i = 0; i<8; i++) {
    if ((data & 1) == 1) del = 6; else del = 60;
    LowRelease(del, 70 - del);
    data = data >> 1;
  }
}

uint8_t OneWireRead () {
  uint8_t data = 0;
  for (int i = 0; i<8; i++) {
    LowRelease(6, 9);
    data = data | PinRead()<<i;
    DelayMicros(55);
  }
  return data;
}

// Read bytes into array, least significant byte first
void OneWireReadBytes (int bytes) {
  for (int i=0; i<bytes; i++) {
    DataBytes[i] = OneWireRead();
  }
}

// Calculate CRC over buffer - 0x00 is correct
uint8_t OneWireCRC (int bytes) {
  uint8_t crc = 0;
  for (int j=0; j<bytes; j++) {
    crc = crc ^ DataBytes[j];
    for (int i=0; i<8; i++) crc = crc>>1 ^ ((crc & 1) ? 0x8c : 0);
  }
  return crc;
}

// Serial Seven-Segment Display **********************************************

const int Select = 0;
const int DataOut = 1;
const int ClockPin = 2;

const int Clear_Display = 0x76;
const int Cursor_Control = 0x79;
const int Decimal_Control = 0x77;

void SendByte(char data) {
 digitalWrite(Select, LOW);
 shiftOut(DataOut, ClockPin, MSBFIRST, data);
 digitalWrite(Select, HIGH);
}

// Clear display
void ClearDisplay () {
  SendByte(Clear_Display);
}

// Display Error
void DisplayError (char *str) {
  SendByte(Clear_Display);
  SendByte(Cursor_Control);
  SendByte(0);
  while (*str) SendByte(*str++);
}

// Display a four digit hexadecimal number
void Display (int n) {
  SendByte(Cursor_Control);
  SendByte(0);
  for (int i=12; i>=0; i=i-4) {
     SendByte((n>>i) & 0x0F);
  }
}

// Display temperature
void DisplayTemp (int t) {
  SendByte(Cursor_Control);
  SendByte(0);
  int temp = t>>4;
  int points = 0x20;                 // Display degree symbol
  if (temp>=100) SendByte(temp/100); // Hundreds
  if (temp<0) SendByte('-');
  SendByte((abs(temp)/10) % 10);     // Tens
  SendByte(abs(temp) % 10);          // Units
  if (temp>=0 && temp<100) {
    points = 0x22;                   // Display decimal point
    SendByte(((t & 0x0F)*10)>>4);    // Tenths
  }
  SendByte(Decimal_Control);
  SendByte(points);
  SendByte('C');
}

// Setup **********************************************

void setup() {
  pinMode(ClockPin, OUTPUT);
  pinMode(DataOut, OUTPUT);
  pinMode(Select, OUTPUT);
  digitalWrite(Select, HIGH);
  digitalWrite(ClockPin, LOW);
  digitalWrite(DataOut, LOW);
  OneWireSetup();
}

// Read temperature of a single DS18B20 or MAX31820 on the bus
void Temperature () {
  cli();                            // No interrupts
  if (OneWireReset() != 0) {
    sei();
    DisplayError("Err");
  } else {
    OneWireWrite(SkipROM);
    OneWireWrite(ConvertT);
    while (OneWireRead() != 0xFF);
    OneWireReset();
    OneWireWrite(SkipROM);
    OneWireWrite(ReadScratchpad);
    OneWireReadBytes(9);
    sei();                          // Interrupts
    if (OneWireCRC(9) == 0) {
      DisplayTemp(DataWords[0]);
    } else DisplayError("Crc");
  }
  delay(1000);
}

// Display serial number of a single device on the 1-wire bus
void SerialNumber () {
  ClearDisplay(); 
  cli();
  if (OneWireReset() != 0) {
    sei();
    DisplayError("Err");
  } else {
    OneWireWrite(ReadROM);
    OneWireReadBytes(8);
    sei();
    if (OneWireCRC(8) == 0) {
      for (int i=3; i>=0; i--) {
        Display(DataWords[i]);
        delay(1000);
      }
    } else DisplayError("Crc");
  }
  delay(1000);
}

void loop () {
  Temperature();
  SerialNumber();
}