DS1302 Real-Time Clock (RTC) C Driver

Overview

The DS1302 is a real-time clock (RTC) module that keeps track of time and date. This C driver allows communication with the DS1302 using a microcontroller over a 3-wire SPI interface (CE, SCLK, I/O).

Currently example only supports for STM32F103, feel free to contact me if you need any help or develop additional features.

Features

• Read and write datetime (SS:MN:HH:DD:MM:WD:YR)

Hardware Requirements

• Microcontroller (e.g., STM32, AVR, ESP32, etc.)
• DS1302 RTC module
• 3 GPIO pins for communication

Example

• Currently support STM32 example, tested on STM32F103C6T6 The example set an initial Date and time and them print it out through UART.

Wiring Diagram

For example STM32F103C6T6, you can find the information in inc/board_config.h or belows:

DS1302 Pin	MCU Pin
CE (RST)	GPIO_A3
SCLK	GPIO_A1
I/O	GPIO_A2
UART (TX)	GPIO_A9
VCC	3.3V/5V
GND	GND

Installation

1. Copy driver files (ds1302.c, ds1302_hw.c and ds1302.h, ds1302_hw.h) into your project.
2. Include the header file in your source code:

   #include "ds1302.h"

Usage

Initialize hardware abstraction for ds1302

void ds1302_com_init(void)
{
  ds1302_hw_ops_t ds1302_hw = {
      .rst_write = hal_gpio_ds1302_rst_write,
      .clk_write = hal_gpio_ds1302_clk_write,
      .dat_set_mode = hal_gpio_ds1302_dat_set_mode,
      .dat_write = hal_gpio_ds1302_dat_write,
      .dat_read = hal_gpio_ds1302_dat_read,
      .delay_us = sw_udelay,
  };
  ds1302_set_hw_spec(&ds1302_hw);
}

int hal_gpio_ds1302_rst_write(uint8_t val)
{
  HAL_GPIO_WritePin(DS1302_RST_PORT, DS1302_RST_PIN, val);
  return 0;
}
...

Initialize MCU hardwares

  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART1_UART_Init();
  ds1302_com_init();

Set Time & Date

  datetime_t set_time = DATETIME_INIT(30, 59, 23, 31, 12, 7, 1); /// 30 secs to happy new year!!!
  ds1302_en_write();
  ds1302_write_time(&set_time, REG_WRITE_BURST);

Read Time & Date

    HAL_Delay(1000);

    /* Read all of the time variables*/
    ds1302_read_time(&time_keeper, REG_READ_BURST);

    hal_uart_prinf("%d:%d:%d:%d:%d:%d:%d \n",
                   time_keeper.seconds,
                   time_keeper.minutes,
                   time_keeper.hours,
                   time_keeper.date,
                   time_keeper.months,
                   time_keeper.weekday,
                   time_keeper.years);

Results:

55:0:0:1:1:1:2 
56:0:0:1:1:1:2 
57:0:0:1:1:1:2 
58:0:0:1:1:1:2 
59:0:0:1:1:1:2 
0:1:0:1:1:1:2 
1:1:0:1:1:1:2 
2:1:0:1:1:1:2 
3:1:0:1:1:1:2 
4:1:0:1:1:1:2 
5:1:0:1:1:1:2 
6:1:0:1:1:1:2 
7:1:0:1:1:1:2 
9:1:0:1:1:1:2 
10:1:0:1:1:1:2 
11:1:0:1:1:1:2 
12:1:0:1:1:1:2 
13:1:0:1:1:1:2 
14:1:0:1:1:1:2 
15:1:0:1:1:1:2 
16:1:0:1:1:1:2 

Notes

• DS1302 operates at 3.3V or 5V.
• connect a backup battery to maintain time when power is lost.

Power Consumption experiment

• Measurement device: Nordic PPK2
• Condition: Input supply to VCC2 (main power souce)
• Result: 30uA @ 2V (datasheet: 25uA) and 88uA @5V (datasheet: 80uA)

License

This driver is open-source and can be used freely in any project.

Author: Binh Pham Contact me: You can find my contact @ https://github.com/ch-binh Version: 1.0
Last Updated: March 2025