STM32 Weather Station with OLED Display

Overview

This project is a real-time embedded weather station built using an STM32 Nucleo F446RE microcontroller. It reads environmental data from a BME280 sensor and displays the results on an SSD1306 OLED screen. The system also includes a real-time clock (RTC) and a multi-button interface for user interaction.

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Features

• Temperature, humidity, and pressure measurement (BME280)

• Real-time clock display (RTC)

• Multiple display screens:

  • Temperature
  • Humidity
  • Pressure
  • Clock

• Button-controlled navigation

• Time setting mode with blinking active field

• Power (sleep/wake) functionality

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Circuit Diagram

The system uses a shared I2C bus for both the BME280 sensor and SSD1306 OLED display. Push buttons are connected with pull-down resistors and handled via external interrupts.

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BME280 Sensor Connections

Pin	STM32	Description
VCC	3.3V	Power
GND	GND	Ground
SCL	PB8	I2C Clock
SDA	PB9	I2C Data
CSB	VCC	I2C mode select
SDO	GND	Address (0x76)

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OLED Display Connections

Pin	STM32	Description
VCC	3.3V	Power
GND	GND	Ground
SCL	PB8	I2C Clock
SDA	PB9	I2C Data

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Button Mapping

Function	Pin	Description
NEXT / MODE	PA5	Screen change / long press for time setting
UP	PA1	Increase value
DOWN	PB0	Decrease value
POWER	PA4	Display ON/OFF

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Operating Modes

Normal Mode

• Switch between screens using NEXT button
• Displays sensor data or clock

Time Setting Mode

• Enter with long press
• Select field (hour/min/sec)
• Adjust using UP/DOWN
• Active field blinks

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Implementation Highlights

• Sensor reading via Bosch BME280 driver
• Interrupt-based button handling (HAL_GPIO_EXTI_Callback)
• Screen rendering using switch-case structure
• Blinking effect using system tick timing
• OLED reinitialization for power control

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File Structure

• main.c → Main application logic
• bme280.* → Sensor driver
• ssd1306.* → OLED driver

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Libraries Used

This project uses the following external libraries:

• BME280 Sensor API (Bosch Official)

  • https://github.com/boschsensortec/BME280_SensorAPI

• SSD1306 OLED Driver (STM32)

  • https://github.com/afiskon/stm32-ssd1306

These libraries were integrated and adapted for use with STM32 HAL.

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Limitations

• RTC is not battery-backed
• UI is text-based only

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Possible Improvements

• Add graphical UI (icons, charts)
• Add non-volatile memory for RTC
• Improve power optimization

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Conclusion

This project demonstrates a clean embedded system design with sensor integration, interrupt-driven input handling, and structured user interface logic.

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