Simple Clock - AVR Weather Station

A comprehensive AVR-based weather station and digital clock project featuring real-time clock, environmental sensors, and an intelligent display system with advanced alarm functionality and power management.

📋 Table of Contents

• Overview
• Features
• Hardware Requirements
• Pin Configuration
• Installation
• Usage
• Project Structure
• API Documentation
• Configuration
• Troubleshooting
• Contributing
• License

🌟 Overview

This project implements a sophisticated weather station and digital clock using an AVR microcontroller (ATmega328P). The system combines multiple sensors to provide real-time environmental data, precise timekeeping, and intelligent display management with automatic brightness control, advanced alarm functionality, and power management features.

✨ Features

Core Functionality

• Real-time Clock: DS3231 RTC module with battery backup
• Environmental Monitoring:
  • Temperature and humidity (DHT22)
  • Barometric pressure (BMP180)
  • Internal temperature from DS3231
• Triple Display Modes:
  • Large digital time display (30 seconds)
  • Calendar and date information (15 seconds)
  • Weather sensor data (15 seconds)
• Advanced Alarm System: Multi-stage alarm with progressive escalation
• Intelligent Brightness Control: Time-based LCD backlight management
• Interactive Controls: Button-based mode switching
• Power Management: Watchdog timer and sleep capabilities

Advanced Features

• Custom LCD Characters: Large digit display using custom character sets
• I2C Communication: Efficient sensor communication protocol
• Interrupt-driven Architecture: Timer-based updates and button handling
• PWM Backlight Control: Smooth brightness transitions
• Musical Alarms: Multiple ringtone patterns for different alarm stages
• Smart Sensor Reading: Optimized sensor polling (every 30 seconds, disabled at night)

🆕 Recent Updates

Version 2.0 Features

• Triple Display System: Enhanced from dual to triple display modes with optimized timing
• Advanced Alarm System: Multi-stage progressive alarm with weekend mode
• Power Management: Watchdog timer implementation for system reliability
• PlatformIO Support: Modern build system integration alongside traditional Make
• Optimized Sensor Reading: Smart polling strategy to reduce power consumption
• Enhanced Brightness Control: More granular time-based brightness management
• Improved Display Content: Better organized weather information display

Key Improvements

• Reliability: Watchdog timer prevents system hangs
• Efficiency: Reduced sensor polling during night hours
• User Experience: Better display mode organization and timing
• Maintainability: PlatformIO integration for easier development

🔧 Hardware Requirements

Microcontroller

• ATmega328P (Arduino Uno compatible)
• Clock Speed: 8MHz (configurable)
• Memory: 32KB Flash, 2KB SRAM

Sensors and Modules

• DS3231 RTC Module: Real-time clock with temperature sensor
• DHT22: Digital temperature and humidity sensor
• BMP180: Barometric pressure sensor
• LCD1602 with I2C Backpack: 16x2 character display
• Buzzer: Piezo buzzer for alarm sounds
• Photoresistor: Ambient light sensing (optional, currently disabled)
• Push Button: Mode switching control

Power Requirements

• Operating Voltage: 5V DC
• Current Consumption: ~100-200mA (depending on display brightness)
• Backup Power: CR2032 battery for RTC (included in DS3231 module)

📌 Pin Configuration

Component	Pin	Function
I2C Bus
SDA	A4 (PC4)	I2C Data Line
SCL	A5 (PC5)	I2C Clock Line
DHT22
Data	PD5	Digital I/O
Buzzer
Signal	PB0	PWM Output
LCD Backlight
PWM	PD3	PWM Control
Button
Mode Switch	PD2	Digital Input (with pull-up)
Photoresistor
Analog	A2 (PC2)	ADC Input (optional)

🚀 Installation

Prerequisites

• AVR-GCC Toolchain: Version 3.4 or later
• AVRDUDE: For programming the microcontroller
• Make: Build system
• Git: Version control

Building the Project

1. Clone the repository:

   git clone <repository-url>
   cd simple-clock

2. Install PlatformIO (if not already installed):

   pip install platformio

3. Build the project:

   pio run

4. Upload to microcontroller:

   pio run --target upload

5. Alternative: Using Make (if preferred):

   make clean
   make all
   make upload

Hardware Assembly

1. Connect I2C devices:

   • DS3231: VCC→5V, GND→GND, SDA→A4, SCL→A5
   • LCD1602: VCC→5V, GND→GND, SDA→A4, SCL→A5 (I2C address: 0x27)

2. Connect sensors:

   • DHT22: VCC→5V, GND→GND, Data→PD5
   • BMP180: VCC→3.3V, GND→GND, SDA→A4, SCL→A5

3. Connect peripherals:

   • Buzzer: Positive→PB0, Negative→GND
   • Button: One terminal→PD2, Other terminal→GND
   • LCD Backlight: PWM control→PD3

📖 Usage

Initial Setup

1. Power on the system - The device will display "Hello World" and perform a countdown

2. Set initial time and date (uncomment in main.c):

   DS3231_setDate(31, 8, 25);  // Day, Month, Year
   DS3231_setTime(10, 52, 0);  // Hour, Minute, Second

3. Configure alarm (optional):

   DS3231_setAlarm2(7, 0);  // 7:00 AM alarm

Display Modes

The system automatically cycles between three display modes:

Mode 0: Large Time Display (30 seconds)

• Shows large, easy-to-read time format using custom characters
• Displays current time in HH:MM:SS format
• Optimized for distance viewing
• Only mode active during night hours (0:00-6:00)

Mode 1: Calendar Display (15 seconds)

• Line 1: Time (HH:MM:SS) and Month abbreviation
• Line 2: Day of month, Full day name, Year
• Shows complete date and time information

Mode 2: Weather Information (15 seconds)

• Line 1: BMP180 temperature, DHT22 temperature, DS3231 temperature
• Line 2: DHT22 humidity, BMP180 pressure (mmHg)
• Only displays during daylight hours (6:00-23:00)
• Sensors read every 30 seconds

Alarm System

The alarm system features progressive escalation with multiple stages:

1. Initial Alarm (at set time): Beep every 15 seconds
2. +1 minute: Beep every 10 seconds
3. +5 minutes: Ringtone every 20 seconds
4. +10 minutes: Alarm beep every 20 seconds
5. +11 minutes: Alarm beep every 15 seconds

Note: Alarm is disabled on Saturdays (weekend mode)

Brightness Control

Automatic brightness adjustment based on time:

• Night (23:00-06:00): Display off (0% brightness)
• Evening (21:00-23:00): Dim (64% brightness)
• Morning (06:00-07:00): Dim (64% brightness)
• Day (07:00-21:00): Full brightness (96%)

📁 Project Structure

simple-clock/
├── src/                    # Source code files
│   ├── main.c             # Main application logic
│   ├── ds3231.c           # RTC module driver
│   ├── lcd1602.c          # LCD display driver
│   ├── dht22.c            # Temperature/humidity sensor
│   ├── bmp180.c           # Pressure sensor driver
│   ├── i2c.c              # I2C communication
│   ├── pwm.c              # PWM control
│   ├── adc.c              # Analog-to-digital conversion
│   ├── buzzer.c           # Audio output
│   └── uart.c             # Serial communication
├── include/               # Header files
│   ├── ds3231.h
│   ├── lcd1602.h
│   ├── dht22.h
│   ├── bmp180.h
│   ├── i2c.h
│   ├── pwm.h
│   ├── adc.h
│   ├── buzzer.h
│   └── uart.h
├── datasheet/             # Component datasheets
├── schemes/               # Circuit diagrams
├── lib/                   # External libraries
├── test/                  # Test files
└── README.md              # This file

📚 API Documentation

DS3231 RTC Module

void DS3231_init(void);
void DS3231_getTime(uint8_t* hour, uint8_t* minute, uint8_t* second);
void DS3231_setTime(uint8_t hour, uint8_t minute, uint8_t second);
void DS3231_getDate(uint8_t* day, uint8_t* month, uint8_t* year);
void DS3231_setDate(uint8_t day, uint8_t month, uint8_t year);
void DS3231_setAlarm2(uint8_t hour, uint8_t minute);
void DS3231_getTemperature(int8_t* temperature);

LCD Display

void lcd_init(void);
void lcd_clear(void);
void lcd_set_cursor(char row, char col);
void lcd_print(const char *str);
void display_large_time2(uint8_t hours, uint8_t minutes, uint8_t seconds);
void create_custom_chars(void);

DHT22 Sensor

void DHT22_Read(uint8_t* humidity_int, uint8_t* humidity_dec, 
                uint8_t* temperature_int, uint8_t* temperature_dec);

BMP180 Sensor

void BMP180_init(void);
float BMP180_readTemperature(void);
float BMP180_readPressure(void);

Buzzer Control

void initTimer2(void);
void playBeep(void);
void playAlarmBeep(void);
void playRingtone2(void);
void playNote(uint16_t frequency, uint16_t duration);
void playMorningScale(void);
void playBugleCall(void);
void playCheerfulWake(void);
void playChimePattern(void);

Power Management

void init_watchdog(void);
void wdt_reset(void);

PWM Control

void pwm_init(int8_t pin);
void pwm_set_duty_cycle(uint8_t duty_cycle);

⚙️ Configuration

Clock Frequency

#define F_CPU 8000000UL  // 8MHz operation

Timer Configuration

#define PRESCALER 1024
#define TARGET_FREQ 1    // 1Hz interrupt

I2C Settings

#define SCL_CLOCK 100000L  // 100kHz I2C clock

Display Timing

// Display mode switching (in main loop)
// 0 → for 0–29 seconds (30 seconds)
// 1 → for 30–44 seconds (15 seconds)  
// 2 → for 45–59 seconds (15 seconds)
current_display_mode = (time_second % 60 < 30) ? 0 : ((time_second % 60 < 45) ? 1 : 2);

Power Management

// Watchdog timer configuration
wdt_enable(WDTO_8S);  // 8-second timeout
WDTCSR |= (1 << WDIE);  // Enable watchdog interrupt

🔧 Troubleshooting

Common Issues

1. LCD Not Displaying:

   • Check I2C connections (SDA→A4, SCL→A5)
   • Verify I2C address (should be 0x27)
   • Ensure proper power supply (5V)

2. Time Not Updating:

   • Check DS3231 connections
   • Verify battery in RTC module
   • Ensure proper I2C communication

3. Sensors Not Reading:

   • Check individual sensor connections
   • Verify power supply for each sensor
   • Test I2C bus with scanner

4. Alarm Not Working:

   • Verify buzzer connection (PB0)
   • Check alarm time setting
   • Ensure Timer2 is properly initialized

5. Display Too Dim/Bright:

   • Check PWM backlight control (PD3)
   • Verify time-based brightness logic
   • Test manual brightness adjustment

Debug Features

Enable UART debugging by uncommenting UART-related code in main.c:

//#include "uart.h"  // Uncomment for debugging
//uart_init(UART_BAUD_SELECT(UART_BAUD_RATE, F_CPU));

Power Management Issues

1. System Hanging:

   • Check watchdog timer configuration
   • Verify wdt_reset() calls in main loop
   • Ensure proper interrupt handling

2. Display Not Updating:

   • Check Timer1 configuration and interrupts
   • Verify update_flag is being set properly
   • Ensure global interrupts are enabled (sei())

🤝 Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Development Guidelines

• Follow existing code style and naming conventions
• Add appropriate comments for complex functions
• Test changes on actual hardware
• Update documentation for new features
• Ensure backward compatibility

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Sergey Denisov - Original LCD library implementation
• Andy Gock - UART library foundation
• Bosch Sensortec - BMP180 sensor documentation
• AVR Community - Various sensor driver implementations
• PlatformIO - Modern embedded development platform

📞 Support

For questions, issues, or contributions:

• Create an issue in the repository
• Check existing documentation and troubleshooting guide
• Review component datasheets in the datasheet/ directory

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Note: This project is designed for educational and hobbyist purposes. Always follow proper electrical safety practices when working with electronic components.

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