Details

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BUY DS12885 https://www.utsource.net/itm/p/12541445.html

Below is the parameter table and instructions for the DS12885 Real-Time Clock (RTC) IC.

DS12885 Parameter Table

Parameter	Symbol	Min	Typ	Max	Unit
Supply Voltage	Vcc	2.0	3.6	5.5	V
Operating Temperature	Ta	-40		+85	°C
Standby Current	Icc	0.2	0.5	1.0	μA
Active Current	Icc	1.0	2.0	3.0	μA
Output Frequency	fOUT	32.768		32.768	kHz
Timekeeping Accuracy		±2		±2	ppm/°C
Data Retention Time				10	Years
Write Cycle Time	tWC	5	10	15	ms
Read Cycle Time	tRC	1	2	3	μs
Reset Pulse Width	tRST	100	200	300	ns
Clock Output Drive Current	IOUT	1.0	2.0	3.0	mA

DS12885 Instructions

1. Powering the Device

• Vcc: Connect the supply voltage to the Vcc pin. The DS12885 operates from 2.0V to 5.5V.
• GND: Connect the ground to the GND pin.

2. Clock Input

• X1 and X2: Connect a 32.768 kHz crystal between the X1 and X2 pins for accurate timekeeping.

3. Reset Pin (RST)

• RST: A low pulse on this pin resets the device. The reset pulse width should be at least 100 ns.

4. Data Communication

• SCL and SDA: Use these pins for I2C communication. The DS12885 has a fixed I2C address.
• CS: Chip select pin for SPI communication. Pull low to enable SPI mode.
• MOSI, MISO, SCK: Used for SPI communication when CS is low.

5. Clock Output (CLKO)

• CLKO: This pin outputs a 32.768 kHz signal. It can be used for external clock synchronization.

6. Battery Backup (VBAT)

• VBAT: Connect a backup battery to this pin to maintain the RTC during power loss. The battery voltage should be between 2.0V and 3.6V.

7. Programming the RTC

• Time and Date Registers: Write the current time and date to the appropriate registers using I2C or SPI.
• Alarm Registers: Set up alarms by writing the desired time to the alarm registers.
• Control Registers: Configure the device settings such as interrupt enable, square wave output, and power-down modes.

8. Reading the RTC

• Time and Date Registers: Read the current time and date from the appropriate registers.
• Status Registers: Check the status of the device, including any pending interrupts or errors.

9. Interrupt Handling

• INT/SQW: This pin can be configured to generate interrupts or square wave outputs. Configure the control registers to enable the desired functionality.

10. Data Retention

• Backup Battery: Ensure the backup battery is connected to maintain data retention during power loss.

Example Code (I2C)

#include <Wire.h>

#define DS12885_I2C_ADDRESS 0x68

void setup() {
  Wire.begin();
  set_time(2023, 10, 1, 12, 0, 0); // Set time to October 1, 2023, 12:00:00
}

void loop() {
  print_time(); // Print the current time
  delay(1000);  // Wait for 1 second
}

void set_time(int year, int month, int day, int hour, int minute, int second) {
  Wire.beginTransmission(DS12885_I2C_ADDRESS);
  Wire.write(0); // Start at the seconds register
  Wire.write(dec_to_bcd(second));
  Wire.write(dec_to_bcd(minute));
  Wire.write(dec_to_bcd(hour));
  Wire.write(dec_to_bcd(day));
  Wire.write(dec_to_bcd(month));
  Wire.write(dec_to_bcd(year % 100));
  Wire.endTransmission();
}

void print_time() {
  Wire.beginTransmission(DS12885_I2C_ADDRESS);
  Wire.write(0); // Start at the seconds register
  Wire.endTransmission();

  Wire.requestFrom(DS12885_I2C_ADDRESS, 7);

  if (Wire.available() == 7) {
    int second = bcd_to_dec(Wire.read());
    int minute = bcd_to_dec(Wire.read());
    int hour = bcd_to_dec(Wire.read());
    int day = bcd_to_dec(Wire.read());
    int month = bcd_to_dec(Wire.read());
    int year = bcd_to_dec(Wire.read()) + 2000; // Assuming 2000-2099
    Serial.print("Time: ");
    Serial.print(hour);
    Serial.print(":");
    Serial.print(minute);
    Serial.print(":");
    Serial.println(second);
    Serial.print("Date: ");
    Serial.print(month);
    Serial.print("/");
    Serial.print(day);
    Serial.print("/");
    Serial.println(year);
  }
}

int dec_to_bcd(int val) {
  return ((val / 10 * 16) + (val % 10));
}

int bcd_to_dec(int val) {
  return ((val / 16 * 10) + (val % 16));
}

This example code sets the time and continuously prints the current time using I2C communication with the DS12885.

(For reference only)