// Copyright 2017 Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland
// www.source-code.biz, www.inventec.ch/chdh
//
// This module is multi-licensed and may be used under the terms of any of the following licenses:
//
//  LGPL, GNU Lesser General Public License, V2.1 or later, http://www.gnu.org/licenses/lgpl.html
//  EPL, Eclipse Public License, V1.0 or later, http://www.eclipse.org/legal
//
// Please contact the author if you need another license.
// This module is provided "as is", without warranties of any kind.
//
// Home page: http://www.source-code.biz/snippets/java/I2cBusDriver

package biz.source_code.utils;

import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.TimeZone;

// Driver for the PCF8563 RTC (real-time clock) chip.
public class PCF8563Driver {

private static final int         slaveAddr = 0x51;
private static final TimeZone    GMT = TimeZone.getTimeZone("GMT");

// Returns 0 if the RTC time is not valid, which is normally caused by a low battery.
public static long getTime (I2cBusDriver i2c) throws Exception {
   byte[] d = i2c.getRegs(slaveAddr, 2, 7);
   if ((d[0] & 0x80) != 0) {
      return 0; }
   int second = decodeBcd(d[0] & 0x7F);
   int minute = decodeBcd(d[1] & 0x7F);
   int hour   = decodeBcd(d[2] & 0x3F);
   int day    = decodeBcd(d[3] & 0x3F);
   int month  = decodeBcd(d[5] & 0x1F);
   int year   = decodeBcd(d[6] & 0xFF) + (((d[5] & 0x80) != 0) ? 1900 : 2000);     // same logic as Uboot
   GregorianCalendar cal = new GregorianCalendar(GMT, Locale.US);
   cal.clear();
   cal.set(year, Math.max(0, month - 1), day, hour, minute, second);
   return cal.getTimeInMillis(); }

public static void setTime (I2cBusDriver i2c, long time) throws Exception {
   GregorianCalendar cal = new GregorianCalendar(GMT, Locale.US);
   cal.setTimeInMillis(time);
   int year    = cal.get(Calendar.YEAR);
   int month   = cal.get(Calendar.MONTH) + 1;
   int day     = cal.get(Calendar.DAY_OF_MONTH);
   int hour    = cal.get(Calendar.HOUR_OF_DAY);
   int minute  = cal.get(Calendar.MINUTE);
   int second  = cal.get(Calendar.SECOND);
   int weekDay = (cal.get(Calendar.DAY_OF_WEEK) + 6) % 7;   // Sunday = 0
   byte[] d = new byte[16];
   d[0] = 0x00;
   d[1] = 0x00;
   d[2] = encodeBcd(second);
   d[3] = encodeBcd(minute);
   d[4] = encodeBcd(hour);
   d[5] = encodeBcd(day);
   d[6] = (byte)weekDay;
   d[7] = (byte)(((year >= 2000 && year <= 2099) ? 0x00 : 0x80) | encodeBcd(month));
   d[8] = (year >= 1900 && year <= 2099) ? encodeBcd(year % 100) : 0;
   d[9] = (byte)0x80;
   d[10] = (byte)0x80;
   d[11] = (byte)0x80;
   d[12] = (byte)0x80;
   d[13] = (byte)0x00;
   d[14] = (byte)0x03;
   d[15] = (byte)0x00;
   i2c.setRegs(slaveAddr, 0, d); }

private static int decodeBcd (int i) {
   int hi = (i & 0xF0) >> 4;
   int lo = (i & 0x0F);
   return hi * 10 + lo; }

private static byte encodeBcd (int i) {
   if (i > 99 || i < 0) {
      return 0; }
   int hi = i / 10;
   int lo = i % 10;
   return (byte)((hi << 4) | lo); }

}