esp8266-clock/main/ds3231.c

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

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

#include <esp_err.h>

#include <stdio.h>
#include <stdlib.h>

#include "bcd.h"

#define DS3231_ADDRESS 0x68
#define SECONDS_REGISTER_ADDRESS 0x00
#define MINUTES_REGISTER_ADDRESS 0x01
#define HOURS_REGISTER_ADDRESS 0x02
#define DOW_REGISTER_ADDRESS 0x03
#define DAY_REGISTER_ADDRESS 0x04
#define MONTH_REGISTER_ADDRESS 0x05
#define YEAR_REGISTER_ADDRESS 0x06


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;
    ESP_ERROR_CHECK(i2c_driver_install(i2c_master_port, conf.mode));
    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_RATE_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_RATE_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_RATE_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(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(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(SECONDS_REGISTER_ADDRESS, &seconds);
	ret &= read_value(MINUTES_REGISTER_ADDRESS, &minutes);
	ret &= read_hour_value(&hours);
	ret &= read_value(DOW_REGISTER_ADDRESS, &dow);
	ret &= read_value(DAY_REGISTER_ADDRESS, &day);
	ret &= read_month_value(&month);
	ret &= read_value(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(SECONDS_REGISTER_ADDRESS, bin2bcd(date_time.tm_sec));
	ret &= write_value(MINUTES_REGISTER_ADDRESS, bin2bcd(date_time.tm_min));
	ret &= write_value(HOURS_REGISTER_ADDRESS, bin2bcd(date_time.tm_hour));
	ret &= write_value(DOW_REGISTER_ADDRESS, bin2bcd(date_time.tm_wday));
	ret &= write_value(DAY_REGISTER_ADDRESS, bin2bcd(date_time.tm_mday));
	ret &= write_value(MONTH_REGISTER_ADDRESS, bin2bcd(date_time.tm_mon) | 0x80);
	ret &= write_value(YEAR_REGISTER_ADDRESS, bin2bcd(date_time.tm_year));
	ret &= write_value(YEAR_REGISTER_ADDRESS, bin2bcd(date_time.tm_year));
	
	return ret;

}