PCF8563 Real-Time Clock (RTC)

// Requires the esp-idf-lib PCF8563 driver from the ESP Component Registry:
//   idf.py add-dependency "esp-idf-lib/pcf8563^1.0.7"

#include <stdio.h>
#include <string.h>
#include <time.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "pcf8563.h"

#define SDA_GPIO GPIO_NUM_21
#define SCL_GPIO GPIO_NUM_22

void app_main(void)
{
    ESP_ERROR_CHECK(i2cdev_init());

    i2c_dev_t dev;
    memset(&dev, 0, sizeof(i2c_dev_t));
    ESP_ERROR_CHECK(pcf8563_init_desc(&dev, 0, SDA_GPIO, SCL_GPIO));

    while (1) {
        struct tm time;
        bool valid;
        if (pcf8563_get_time(&dev, &time, &valid) == ESP_OK)
            printf("%04d-%02d-%02d %02d:%02d:%02d (%s)\n",
                   time.tm_year + 1900, time.tm_mon + 1, time.tm_mday,
                   time.tm_hour, time.tm_min, time.tm_sec,
                   valid ? "valid" : "voltage low - time may be wrong");
        else
            printf("Could not read time from RTC\n");
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

i2c:
  sda: GPIO21
  scl: GPIO22

time:
  - platform: pcf8563
    id: rtc_time

text_sensor:
  - platform: template
    name: "PCF8563 Date and Time"
    lambda: |-
      char buf[20];
      auto now = id(rtc_time).now();
      if (!now.is_valid()) return {"unknown"};
      now.strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S");
      return {buf};
    update_interval: 1s

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
lib_deps =
    elpaso/Rtc_Pcf8563

#include <Arduino.h>
#include <Wire.h>
#include <Rtc_Pcf8563.h>

Rtc_Pcf8563 rtc;

void setup() {
    Serial.begin(115200);
    Wire.begin(21, 22); // SDA: GPIO21, SCL: GPIO22
    rtc.initClock();
    // day, weekday, month, century (0 = 20xx), year (0-99)
    rtc.setDate(1, 2, 9, 0, 26);  // Tuesday 2026-09-01
    // second, minute, hour
    rtc.setTime(0, 30, 14);       // 14:30:00
}

void loop() {
    Serial.print("Time: ");
    Serial.print(rtc.getHour());
    Serial.print(":");
    Serial.print(rtc.getMinute());
    Serial.print(":");
    Serial.println(rtc.getSecond());
    Serial.print("Date: ");
    Serial.print(rtc.getDay());
    Serial.print("/");
    Serial.print(rtc.getMonth());
    Serial.print("/");
    Serial.println(rtc.getYear());
    delay(1000);
}

from machine import I2C, Pin
import time

# PCF8563 I2C address
PCF8563_ADDRESS = 0x51

def bcd_to_decimal(bcd):
    return (bcd >> 4) * 10 + (bcd & 0x0F)

def decimal_to_bcd(decimal):
    return ((decimal // 10) << 4) | (decimal % 10)

def set_time(i2c, year, month, day, hour, minute, second):
    data = [decimal_to_bcd(second), decimal_to_bcd(minute), decimal_to_bcd(hour),
            0, decimal_to_bcd(day), decimal_to_bcd(month), decimal_to_bcd(year - 2000)]
    i2c.writeto_mem(PCF8563_ADDRESS, 0x02, bytes(data))

def get_time(i2c):
    data = i2c.readfrom_mem(PCF8563_ADDRESS, 0x02, 7)
    second = bcd_to_decimal(data[0] & 0x7F)
    minute = bcd_to_decimal(data[1] & 0x7F)
    hour = bcd_to_decimal(data[2] & 0x3F)
    day = bcd_to_decimal(data[3] & 0x3F)
    month = bcd_to_decimal(data[5] & 0x1F)
    year = bcd_to_decimal(data[6]) + 2000
    return year, month, day, hour, minute, second

# Initialize I2C
i2c = I2C(0, scl=Pin(22), sda=Pin(21))

# Set initial time
set_time(i2c, 2023, 12, 4, 14, 30, 0)

# Loop to read time
while True:
    year, month, day, hour, minute, second = get_time(i2c)
    print(f"Time: {hour:02}:{minute:02}:{second:02}, Date: {year:04}/{month:02}/{day:02}")
    time.sleep(1)