// Basic RTC clock with LED display using Attiny85
// Work-in-progress!!!
// TODO: Time not running

#include <TinyWireM.h>

// DS1307 related
#define DS1307_ADDR 0x68
byte seconds,minutes,hours;

// Display related
#define latchPin 3 //STCP
#define clockPin 5 //SHCP
#define dataPin 4  //DS
const uint8_t digitToSegment[] = {
 // ABCDEFGx encoded 0123456789_--1
 0b11111100, 0b01100000, 0b11011010, 0b11110010, 0b01100110,
 0b10110110, 0b10111110, 0b11100000, 0b11111110, 0b11110111,
 0b00000000, 0b00000010, 0b01100010
};

const int dms = 950;

byte d1 = 1;
byte d2 = 2;
byte d3 = 3;
byte d4 = 4;


void setup() {
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  digitalWrite(clockPin, LOW);
  
  TinyWireM.begin(); //SDA=PB0, SCL=PB2
  delay(100);
}

void loop() {
    // release latch
    digitalWrite(latchPin, LOW);
    // shift out the bits
    shiftOut(dataPin, clockPin, LSBFIRST, ~digitToSegment[d4]);
    shiftOut(dataPin, clockPin, LSBFIRST, ~digitToSegment[d3]);
    shiftOut(dataPin, clockPin, LSBFIRST, ~digitToSegment[d2]);
    shiftOut(dataPin, clockPin, LSBFIRST, ~digitToSegment[d1]);

    //latch output
    digitalWrite(latchPin, HIGH);
    // pause before next value:
    delay(dms);
  
  
  
  //reload time from RTC
  getTime();

}

void getTime(){
  byte wireRet = 0;
  
  TinyWireM.beginTransmission(DS1307_ADDR); // reset DS1307 register pointer 
  TinyWireM.write(0); 
  wireRet = TinyWireM.endTransmission(); 
  if (wireRet) delay(1500);
  wireRet = TinyWireM.requestFrom(DS1307_ADDR, 3);    // request n bytes from DS1307
  if (wireRet) delay(1500);

  seconds = bcdToDec(TinyWireM.read());  //read bytes received
  minutes = bcdToDec(TinyWireM.read());      
  hours = bcdToDec(TinyWireM.read());        
}

byte bcdToDec(byte val) {               // Convert binary coded decimal to normal decimal numbers
  return (val>>4) * 10 + (val & 15);
  //Each set of 4 bits represents a digit
}
byte decToBcd(byte val) {               // Convert to BCD
  return (int)(val/10)*16 + val - 10*(int)(val/10);
}

void setTime() {
  byte wireRet = 0;
  TinyWireM.beginTransmission(DS1307_ADDR);
  TinyWireM.write(0); // reset register pointer  
  TinyWireM.write(decToBcd(seconds)); // write the seconds, with the stop bit clear to restart
  TinyWireM.write(decToBcd(minutes));
  TinyWireM.write(decToBcd(hours));
  wireRet = TinyWireM.endTransmission(); 
  return wireRet;
}