File content as of revision 4:0c07690cb24f:

/*
 * mbed library program
 *  Control M41T62 RTC Module
 *
 * Copyright (c) 2014,'15,'17 Kenji Arai / JH1PJL
 *  http://www.page.sannet.ne.jp/kenjia/index.html
 *  http://mbed.org/users/kenjiArai/
 *      Created: June       21st, 2014
 *      Revised: August     23rd, 2017
 */
/*
 *---------------- REFERENCE ----------------------------------------------------------------------
 *  http://www.st-japan.co.jp/web/jp/catalog/sense_power/FM151/CL1410/SC403/PF82507
 *  http://strawberry-linux.com/catalog/items?code=12062
 */

#include "mbed.h"
#include "m41t62_rtc.h"

M41T62::M41T62 (PinName p_sda, PinName p_scl)
 : _i2c_p(new I2C(p_sda, p_scl)), _i2c(*_i2c_p)
{
    M41T62_addr = M41T62ADDR;
    _i2c.frequency(100000);
}

M41T62::M41T62 (I2C& p_i2c)
 : _i2c(p_i2c)
{
    M41T62_addr = M41T62ADDR;
    _i2c.frequency(100000);
}

void M41T62::read_rtc_std (tm *t)
{
    rtc_time time;

    read_rtc_direct(&time);
    t->tm_sec  = time.rtc_seconds;
    t->tm_min  = time.rtc_minutes;
    t->tm_hour = time.rtc_hours;
    t->tm_mday = time.rtc_date;
    if ( time.rtc_weekday == RTC_Wk_Sunday) {
        t->tm_wday = 0; // Sun is not 7 but 0
    } else {
        t->tm_wday = time.rtc_weekday;
    }
    t->tm_mon  = time.rtc_month - 1;
    t->tm_year = time.rtc_year_raw + 100;
    t->tm_isdst= 0;
}

void M41T62::write_rtc_std (tm *t)
{
    rtc_time time;

    time.rtc_seconds  = t->tm_sec;
    time.rtc_minutes  = t->tm_min;
    time.rtc_hours    = t->tm_hour;
    time.rtc_date     = t->tm_mday;
    if ( t->tm_wday == 0) {
        time.rtc_weekday = RTC_Wk_Sunday;
    } else {
        time.rtc_weekday = t->tm_wday;
    }
    time.rtc_month    = t->tm_mon + 1;
    time.rtc_year_raw = t->tm_year - 100;
    write_rtc_direct(&time);
}

void M41T62::read_rtc_direct (rtc_time *tm)
{
    uint8_t eep_dt;

    eep_dt = M41T62_REG_SSEC;
    _i2c.write((int)M41T62_addr, (char *)eep_dt, 1);
    _i2c.read((int)M41T62_addr, (char *)rtc_buf, 8);
    tm->rtc_seconds = bcd2bin(rtc_buf[M41T62_REG_SEC]  & 0x7f);
    tm->rtc_minutes = bcd2bin(rtc_buf[M41T62_REG_MIN]  & 0x7f);
    tm->rtc_hours   = bcd2bin(rtc_buf[M41T62_REG_HOUR] & 0x3f);
    tm->rtc_date    = bcd2bin(rtc_buf[M41T62_REG_DAY]  & 0x3f);
    tm->rtc_weekday = rtc_buf[M41T62_REG_WDAY] & 0x07;
    tm->rtc_month   = bcd2bin(rtc_buf[M41T62_REG_MON]  & 0x1f);
    tm->rtc_year_raw= bcd2bin(rtc_buf[M41T62_REG_YEAR]);
    tm->rtc_year = tm->rtc_year_raw + 100 + 1900;
}

void M41T62::write_rtc_direct (rtc_time *tm)
{
    uint8_t eep_dt;

    eep_dt = M41T62_REG_SSEC;
    _i2c.write((int)M41T62_addr, (char *)eep_dt, 1);
    _i2c.read((int)M41T62_addr, (char *)rtc_buf, 8);
    rtc_buf[0] = M41T62_REG_SSEC;
    rtc_buf[M41T62_REG_SSEC + 1] = 0;
    rtc_buf[M41T62_REG_YEAR + 1] = bin2bcd(tm->rtc_year_raw);
    rtc_buf[M41T62_REG_MON  + 1] = bin2bcd(tm->rtc_month)   | (rtc_buf[M41T62_REG_MON]  & ~0x1f);
    rtc_buf[M41T62_REG_DAY  + 1] = bin2bcd(tm->rtc_date)    | (rtc_buf[M41T62_REG_DAY]  & ~0x3f);
    rtc_buf[M41T62_REG_WDAY + 1] = (tm->rtc_weekday & 0x07) | (rtc_buf[M41T62_REG_WDAY] & ~0x07);
    rtc_buf[M41T62_REG_HOUR + 1] = bin2bcd(tm->rtc_hours)   | (rtc_buf[M41T62_REG_HOUR] & ~0x3f);
    rtc_buf[M41T62_REG_MIN  + 1] = bin2bcd(tm->rtc_minutes) | (rtc_buf[M41T62_REG_MIN]  & ~0x7f);
    rtc_buf[M41T62_REG_SEC  + 1] = bin2bcd(tm->rtc_seconds) | (rtc_buf[M41T62_REG_SEC]  & ~0x7f);
    _i2c.write((int)M41T62_addr, (char *)rtc_buf, 9);
}

void M41T62::frequency(int hz)
{
    _i2c.frequency(hz);
}

void M41T62::set_sq_wave (uint8_t sqw_dt)
{
    uint8_t eep_dt[2];

    // set SQW frequency
    eep_dt[0] = M41T62_REG_WDAY;
    _i2c.write((int)M41T62_addr, (char *)eep_dt, 1);
    _i2c.read((int)M41T62_addr, (char *)eep_dt, 1);
    eep_dt[1] = (eep_dt[0] & 0x07) | (sqw_dt << 4);
    eep_dt[0] = M41T62_REG_WDAY;
    _i2c.write((int)M41T62_addr, (char *)rtc_buf, 2);
    // set or clear SQWE
    eep_dt[0] = M41T62_REG_ALARM_MON;
    _i2c.write((int)M41T62_addr, (char *)eep_dt, 1);
    _i2c.read((int)M41T62_addr, (char *)eep_dt, 1);
    eep_dt[1] = (eep_dt[0] & 0x07) | (sqw_dt << 4);
    eep_dt[0] = M41T62_REG_WDAY;
    _i2c.write((int)M41T62_addr, (char *)rtc_buf, 2);
    if (sqw_dt == RTC_SQW_NONE) {   // Clear SQWE
        eep_dt[1] = eep_dt[0] & 0xbf;
    } else {                        // Set SQWE
        eep_dt[1] = eep_dt[0] | 0x40;
    }
    eep_dt[0] = M41T62_REG_ALARM_MON;
    _i2c.write((int)M41T62_addr, (char *)rtc_buf, 2);
}

uint8_t M41T62::bin2bcd (uint8_t dt)
{
    uint8_t bcdhigh = 0;

    while (dt >= 10) {
        bcdhigh++;
        dt -= 10;
    }
    return  ((uint8_t)(bcdhigh << 4) | dt);
}

uint8_t M41T62::bcd2bin (uint8_t dt)
{
    uint8_t tmp = 0;

    tmp = ((uint8_t)(dt & (uint8_t)0xf0) >> (uint8_t)0x4) * 10;
    return (tmp + (dt & (uint8_t)0x0f));
}