esp32-alarm-clock/main/ds3231.c

/*
 * SPDX-FileCopyrightText: 2022 Helmut Pozimski <helmut@pozimski.eu>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 */

#include <driver/i2c.h>
#include <esp_err.h>
#include <time.h>

#include "bcd.h"

#define DS3231_ADDRESS 0x68
#define CLOCK_SECONDS_REGISTER_ADDRESS 0x00
#define CLOCK_MINUTES_REGISTER_ADDRESS 0x01
#define CLOCK_HOURS_REGISTER_ADDRESS 0x02
#define CLOCK_DOW_REGISTER_ADDRESS 0x03
#define CLOCK_DAY_REGISTER_ADDRESS 0x04
#define CLOCK_MONTH_REGISTER_ADDRESS 0x05
#define CLOCK_YEAR_REGISTER_ADDRESS 0x06
#define ALRM1_SECONDS_REGISTER_ADDRESS 0x07
#define ALRM1_MINUTES_REGISTER_ADDRESS 0x08
#define ALRM1_HOURS_REGISTER_ADDRESS 0x09
#define ALRM1_DAY_DATE_REGISTER_ADDRESS 0x0A
#define CONTROL_REGISTER 0x0E
#define STATUS_REGISTER 0x0F


esp_err_t ds3231_init(int sda_pin, int scl_pin) {
    int i2c_master_port = I2C_NUM_0;
    i2c_config_t conf;
    conf.mode = I2C_MODE_MASTER;
    conf.sda_io_num = sda_pin;
    conf.sda_pullup_en = 1;
    conf.scl_io_num = scl_pin;
    conf.scl_pullup_en = 1;
    conf.clk_flags = 0;
    conf.master.clk_speed = 100000;
    ESP_ERROR_CHECK(i2c_driver_install(i2c_master_port, conf.mode, 0, 0, 0));
    ESP_ERROR_CHECK(i2c_param_config(i2c_master_port, &conf));
    return ESP_OK;
}

static esp_err_t read_value(uint8_t register_addr, uint8_t *value_read) {
    esp_err_t ret;
    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
    i2c_master_start(cmd);
    i2c_master_write_byte(cmd, DS3231_ADDRESS << 1 | I2C_MASTER_WRITE, 0x01);
    i2c_master_write_byte(cmd, register_addr, 0x01);
    i2c_master_stop(cmd);
    ret = i2c_master_cmd_begin(I2C_NUM_0, cmd, 1000 / portTICK_PERIOD_MS);
    i2c_cmd_link_delete(cmd);

    if (ret != ESP_OK) {
        return ret;
    }

    cmd = i2c_cmd_link_create();
    i2c_master_start(cmd);
    i2c_master_write_byte(cmd, 0x68 << 1 | I2C_MASTER_READ, 0x01);
    i2c_master_read(cmd, value_read, 1, 0x02);
    i2c_master_stop(cmd);
    i2c_master_cmd_begin(I2C_NUM_0, cmd, 1000 / portTICK_PERIOD_MS);
    i2c_cmd_link_delete(cmd);

    return ret;

}

static esp_err_t write_value(uint8_t register_addr, uint8_t write_value) {
    esp_err_t ret;
    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
    i2c_master_start(cmd);
    i2c_master_write_byte(cmd, DS3231_ADDRESS << 1 | I2C_MASTER_WRITE, 0x01);
    i2c_master_write_byte(cmd, register_addr, 0x01);
    i2c_master_write_byte(cmd, write_value, 0x01);
    i2c_master_stop(cmd);
    ret = i2c_master_cmd_begin(I2C_NUM_0, cmd, 1000 / portTICK_PERIOD_MS);
    i2c_cmd_link_delete(cmd);

    return ret;

}

static uint8_t convert_12h_to_24h(uint8_t value_read) {
    uint8_t cleaned_value = value_read & 0xBF;
    if (value_read & 0x10) {
        cleaned_value = cleaned_value & 0XDF;
        return bcd_first_digit_value_bin(cleaned_value)
               + 12 + bcd_last_digit_value_bin(cleaned_value);
    }
    return bcd_first_digit_value_bin(cleaned_value)
           + bcd_last_digit_value_bin(cleaned_value);
}

static esp_err_t read_hour_value(uint8_t *hour_value) {
    uint8_t value_read;
    esp_err_t ret = read_value(CLOCK_HOURS_REGISTER_ADDRESS, &value_read);

    if (ret != ESP_OK) {
        return ret;
    }

    if (value_read & 0x20) {
        *hour_value = convert_12h_to_24h(value_read);
    } else {
        *hour_value = bcd2bin(value_read);
    }

    return ret;
}

static esp_err_t read_month_value(uint8_t *month_value) {
    uint8_t value_read;
    esp_err_t ret = read_value(CLOCK_MONTH_REGISTER_ADDRESS, &value_read);
    if (ret == ESP_OK) {
        *month_value = bcd2bin(value_read & 0x7F);
    }
    return ret;
}

esp_err_t ds3231_read_date_time(struct tm *date_time) {
    esp_err_t ret;
    uint8_t seconds, minutes, hours, dow, day, month, year;
    ret = read_value(CLOCK_SECONDS_REGISTER_ADDRESS, &seconds);
    ret |= read_value(CLOCK_MINUTES_REGISTER_ADDRESS, &minutes);
    ret |= read_hour_value(&hours);
    ret |= read_value(CLOCK_DOW_REGISTER_ADDRESS, &dow);
    ret |= read_value(CLOCK_DAY_REGISTER_ADDRESS, &day);
    ret |= read_month_value(&month);
    ret |= read_value(CLOCK_YEAR_REGISTER_ADDRESS, &year);

    date_time->tm_sec = bcd2bin(seconds);
    date_time->tm_min = bcd2bin(minutes);
    date_time->tm_hour = hours;
    date_time->tm_wday = bcd2bin(dow);
    date_time->tm_mday = bcd2bin(day);
    date_time->tm_mon = month;
    date_time->tm_year = bcd2bin(year);

    return ret;

}

esp_err_t ds3231_write_date_time(struct tm date_time) {
    esp_err_t ret;
    ret = write_value(CLOCK_SECONDS_REGISTER_ADDRESS, bin2bcd(date_time.tm_sec));
    ret |= write_value(CLOCK_MINUTES_REGISTER_ADDRESS, bin2bcd(date_time.tm_min));
    ret |= write_value(CLOCK_HOURS_REGISTER_ADDRESS, bin2bcd(date_time.tm_hour));
    ret |= write_value(CLOCK_DOW_REGISTER_ADDRESS, bin2bcd(date_time.tm_wday));
    ret |= write_value(CLOCK_DAY_REGISTER_ADDRESS, bin2bcd(date_time.tm_mday));
    ret |= write_value(CLOCK_MONTH_REGISTER_ADDRESS, bin2bcd(date_time.tm_mon) | 0x80);
    ret |= write_value(CLOCK_YEAR_REGISTER_ADDRESS, bin2bcd(date_time.tm_year));

    return ret;
}

esp_err_t ds3231_set_alrm1(struct tm date_time, uint16_t mode) {
    esp_err_t ret;
    ret = write_value(ALRM1_SECONDS_REGISTER_ADDRESS, bin2bcd(date_time.tm_sec) | ((mode & 0x01) << 7));
    ret |= write_value(ALRM1_MINUTES_REGISTER_ADDRESS, bin2bcd(date_time.tm_min) | ((mode & 0x02) << 6));
    ret |= write_value(ALRM1_HOURS_REGISTER_ADDRESS, bin2bcd(date_time.tm_hour) | ((mode & 0x04) << 5));
    ret |= write_value(ALRM1_DAY_DATE_REGISTER_ADDRESS, bin2bcd(date_time.tm_mday) | ((mode & 0x08) << 4));
    return ret;
}

esp_err_t ds3231_enable_arlm1_interrupt() {
    return write_value(CONTROL_REGISTER, 0x1D);
}

esp_err_t ds3231_acknowledge_alrm1() {
    esp_err_t ret;
    uint8_t register_value;
    ret = read_value(STATUS_REGISTER, &register_value);
    register_value ^= 0x01;
    ret |= write_value(STATUS_REGISTER, register_value);
    return ret;
}

esp_err_t ds3231_disable_32khz_output() {
    esp_err_t ret;
    uint8_t register_value;
    ret = read_value(STATUS_REGISTER, &register_value);
    register_value ^= 0x08;
    ret |= write_value(STATUS_REGISTER, register_value);
    return ret;
}